Veterinary Clinical Pathology
兽医临床病理学
主讲：唐兆新教授
Prof,Zhaoxin Tang
College of Veterinary Medicine,South China Agricultural
University,Guangzhou,China,510642
Preface
Veterinary Clinical Pathology:
Veterinary Laboratory Medicine
Include:
1 Clinical Hematology
2 Clinical biochemistry
3 Clinical cytology
4 Clinical microbiology
5 Clinical parasitology
6 Clinical toxicology
Preface
General Laboratory concepts
Veterinarians have many choices regarding
laboratory testing,Important factors include:
--Need and usefulness
--Practicality
--Cost-effectiveness
--Accuracy
--Turnaround time
Complete Blood Count and Bone Marrow
Examination:general comments and
selected techniques
? Complete blood count
? Quantitation techniques
? Blood smear analysis
? Other determinations
? Bone marrow examination
? Bone marrow biopsy and aspirate
Complete blood count (CBC)
? CBC is a profile of tests used to describe the
quantity and quality of the cellular elements in
blood and a few substances in plasma.
? CBC is a cost-effective screen the detects many
abnormalities and disease conditions.
? Bone marrow examination is used in selected
instances to answer questions the more readily
available CBC cannot.
Quantitation Techniques
? Sample submission
? Microhemotcrit
? Hemoglobin concentration
? Cell counts
? Absolute nucleated RBC count
? Automated hematology cell counters
Blood Smear Analysis
? Making the smear
? Stains
? Evaluating blood smears
--platelet morphology
--leukocyte morphology
--leukocyte estimation
--leukocyte differential count
--erythrocyte morphology
Bone Marrow Examination
? Bone marrow is usually examined to answer
certain question that arose from evaluating the
CBC.
? Indications for bone marrow examination
include:
--nonregenerative anemia
--Persistent neutropenia
--Persistent thrombocytopenia
--Unexplained polycythemia or thrombocytosis
--Atypical cells in blood
Erythrocytes
? Basic concepts of erythrocyte
function,metabolism,production and
breakdown
? Heme synthesis
? Globin synthesis
? Iron metabolism
Erythrocyte metabolism
? Embden-meyerhof pathway
--Glycolysis generates ATP and NADH
? Pentose phosphate pathway
--This pathway produces NADPH
? Methemoblobin reductase pathway
--Methemoglobin(Fe3+) cannot transport oxygen
? Rapoport-luebering pathway
--2,3 diphosphoglycerate(2,3 DPG)
Red blood cells
The fundamental stimulus for production of red blood
cells (erythropoiesis) is erythropoietin(红细胞生成素 ）,
a glycoprotein produced by the kidneys in response to
renal tissue hypoxia,Other hormones,such as
corticosteroids,thyroid hormone and androgens,
stimulate the production or release of erythropoietin
but have no intrinsic erythropoietic activity.
The average lifespan of a circulating erythrocyte is 110-
120 days in the dog and 68 days in the cat,Aged or
damaged red cells are removed primarily by
macrophages in the liver,spleen and bone marrow,
Neutrophils
The production of neutrophils,eosinophils and basophils is termed
granulopoiesis,
The neutrophils in the bloodstream either circulate freely (the circulating
pool) or adhere to the vascular endothelium (the marginal pool),In the
dog the marginal pool and the circulating pool are approximately equal in
size,whilst in the cat the marginal pool is two to three times larger than
the circulating pool,There is a continual exchange of cells between these
two pools,
The half-life of circulating neutrophils is only 6-14 hours,after which time
they leave the circulation and pass into the tissue pool,The circulating
time is shortened during acute infections as neutrophils pass to the site of
infection in the tissues,The main function of the neutrophil is the
phagocytosis of pyogenic bacteria,
Lymphocytes
Lymphoid primitive stem cells divide and differentiate into pre-B
lymphocytes and pre-T lymphocytes in the bone marrow,Pre-T
lymphocytes mature and proliferate into T cells in the thymus,Pre-B
cells proliferate in the bone marrow and migrate to peripheral lymphoid
organs (spleen and lymph nodes) where further proliferation takes place,
Platelets
Platelets are produced from the cytoplasm of megakaryocytes
Once in the circulation,platelets survive for 8-12 days,Up to 20-30% of
circulating platelets can be sequestered in the spleen; the figure may be a
high as 90% if there is splenomegaly,
Old or damaged platelets are removed from the circulation by the spleen,
liver and bone marrow,
ROUTINE HAEMATOLOGY
The complete blood count is an integral part of the diagnostic investigation of
any systemic disease process,It consists of two components:
A quantitativeexamination of the cells,including,
packed cell volume (PCV)
total red cell count (RBC)
total white cell count(WBC)
differential white cell count
platelet count
mean corpuscular volume (MCV),
mean corpuscular haemoglobin (MCH),
mean corpuscular haemoglobin concentration (MCHC),
total plasma protein concentration.
A qualitative examination of blood smears for changes in cellular morphology.
Table 1 Reference values for red cell indices
Dogs Cats
Total red blood cells(x1012/L) 5.5~8.5 5.0~10.0
Haemoglobin(g/dl) 12.0~18.0 8.0~15.0
PCV (L/L) 0.37~0.55 0.26~0.45
MCV (fl) 60.0~77.0 39.0~55.0
MCH (pg) 19.5~24.5 12.5~17.5
MCHC (g/dl) 32.0~37.0 30.0~36.0
ROUTINE HAEMATOLOGY
RED BLOOD CELL INDICES
MCV(fl飞升 )= PCV (L/L) × 1000/ total red cells (× 1012/L)
MCH (pg皮克 ) = total haemoglobin (g/dl) × 10/ total red blood
cells (× 1012/L)
MCHC (g/dl) = total haemoglobin (g/dl)/PCV (L/L)
RBC indices are helpful in the classification of
certain anemias.
ROUTINE HAEMATOLOGY
Differential white cell counts
?The differential white cell count is performed by
counting 200 leucocytes in a blood smear,
?The cells are counted along the long edge of the
smear,using the battlement meander method,four
high-power fields are counted in one direction,then
four more in a direction at right angles to the first,
and so on,following the shape of a battlement,
?The percentage of each type of cell is determined,
?This percentage is then multiplied by the total white
cell count to obtain an absolute count for each cell
type,
ROUTINE HAEMATOLOGY
Plasma protein concentration
(Reference range,60-80 g/1 for the dog and cat)
?Total plasma protein (TPP) and PCV should be interpreted
together,
?Qualitative examination of a blood smear
A blood smear should always be evaluated when automated
cell counts are made or when in-practice instrumentation is
limited to a centrifuge for PCV
?Preparation of a blood smear
?A small drop of blood is placed on one end of a glass slide,
using a capillary tube,A spreader slide (made by breaking
off the comer of another slide,after scoring it with a glass
cutter or diamond writer) is placed on to the slide holding
the blood drop,in front of the drop and at an angle of 20-
40°,
ROUTINE HAEMATOLOGY
ANAEMIA
?Anaemia is characterized by an absolute decrease in red cell count,
haemoglobin concentration and PCV,
Acute haemorrhage
?Acute haemorrhage may be due to trauma or surgery,bleeding
gastrointestinal ulcers or tumours,rupture of a vascular tumour (e.g,
splenic haemangiosarcoma),or a coagulopathy (e.g,warfarin toxicity),
?Immediately following acute haemorrhage the red cell parameters,
including PCV,are normal because both red cells and plasma have been
lost in proportion,Compensatory mechanisms such as splenic
contraction may further offset any fall in PCV,The PCV falls when
blood volume is replaced by interstitial fluid and so does not indicate the
full magnitude of blood loss for at least 24 hours after the onset of
haemorrhage,
ROUTINE HAEMATOLOGY
?Chronic haemorrhage
Chronic external blood loss (e.g,chronic gastrointestinal haemorrhage,
renal or bladder neoplasia) initially results in a regenerative anaemia
but gradually the anaemia becomes non-regenerative as the iron stores
become depleted,Young animals become iron-deficient more bone
marrow is already very active producing red cells quickly than adults
following blood loss,partly because they have low iron stores and
partly because their to match their growth rate and so has less capacity
to increase its rate of haemopoiesis,
?Haemolytic anaemias
Most cases of haemolytic anaemia are immune-mediated,In the dog most
cases of immune-mediated is haemolytic anaemia (IHA) are primary
(idiopathic) and are termed autoimmune haemolytic anaemia (AIHA),
IHA may occur in association with,drugs(e.g,potentiated
sulphonamides); lymphoreticular diseases (e.g,lymphoid leukaemia);
systemic lupus erythematosus; or infections (e.g,Babesia,bacterial
endocarditis),
ROUTINE HAEMATOLOGY
DISORDERS OF WHITE CELL NUMBER
Neutrophilia
Figure 3.20 Causes of neutrophilia
Physiological response (fear,excitement,exercise)
Stress/corticosteroid-induced
Acute inflammatory response,bacterial infection (localized
or generalized),immune-mediated disease,
necrosis,e.g.pancreatitis,neoplasia,especially with tumor
necrosis.
Chronic granulocytic leukaemia
Neutrophil dysfunction
Paraneoplastic syndromes
Neutropenia
The three main causes of neutropenia are,
? An overwhelming demand for neutrophils
? Reduced production of neutrophils in the bone marrow
? Defective neutrophil maturation in the bone marrow,
?An overwhelming demand for neutrophils may occur with
peracute bacterial infections,especially Gram-negative
sepsis and endotoxaemia,
?Other possible causes include peritonitis,pyometra（子宫蓄脓）,
aspiration pneumonia and canine parvovirus infection,
DISORDERS OF WHITE CELL NUMBER
Eosinophilia
?Eosinophils are distributed in the body among various pools in a similar
way to neutrophils,although the bone marrow storage pool is minimal,
Eosinophils circulate in the bloodstream for only a few hours before
entering the tissues,where they may live for several days,Their two main
functions are to kill parasites and to regulate allergic and inflammatory
reactions,
Eosinopenia
?Eosinopenia in combination with lymphopenia occurs following stress,
administration of corticosteroids and in spontaneous
hyperadrenocorticism (Cushing's syndrome),
Basophilia
?Basophils contain inflammatory mediators such as histamine and heparin
and function in a similar manner to mast cells in hypersensitivity
reactions,
DISORDERS OF WHITE CELL NUMBER
Lymphocytosis
Causes of lymphocytosis
1,Physiological lymphocytosis,with concomitant
neutrophilia,in response to excitement (especially cats)
2,Strong immune stimulation (e.g,in chronic infection,
viraemia or immune-mediated disease)
3,Chronic lymphocytic leukaemia
4,Hypoadrenocortiscism (lymphocytosis may be associated
with an eosinophilia)
5,Increased numbers of large reactive lymphocytes may
occur transiently following vaccination
6,Young animals have a higher lymphocyte count than adult
animals
DISORDERS OF WHITE CELL NUMBER
Lymphopenia
Causes of lymphopenia are listed.
Stress
Glucocorticoid therapy
Hyperadrenocorticism
Chylothorax (loss of lymphocytes into the pleural space)
Lymphangiectasia (loss of lymphocytes into the gut)
Acute phase of most viral infections (e.g,canine distemper,parvovirus,FeLV)
Septicaemia/endotoxaemia
DISORDERS OF WHITE CELL NUMBER
Dogs Cats
percentage Absolute value percentage Absolute value(10/
Total WBC N/a 6~17 N/a 5.5~19.5
Band
neutropils 0~3 0~0.3 0~3 0~0.3
Neutropils 60~77 3~11.5 35~37 2.5~12.5
Lymphocytes 12~30 1~4.8 20~55 1.5~7
Monocytes 3~10 0.2~1.5 1~4 0~1.5
Eosinopils 2~10 0.1~1.3 2~12 0~1.5
basopils rare rare rare Rare
Reference ranges for total and differential white blood cell counts
Table 2 shows the alterations in some of parameters in various
diseases.
Laboratory assessment
Tests to assess primary haemostasis include:
Platelet count
Bleeding time
Clot retraction.
Tests to assess secondary haemostasis include:
Whole blood clotting time (WBCT)
Activated clotting time (ACT)
Activated partial thromboplastin time (APPT)
One-stage prothrombin time (OSPT)
Thrombin time (TT)
DISORDERS OF WHITE CELL NUMBER
Disseminated intravascular coagulation (DIC),This may be triggered by a
wide variety of diseases,including
?endotoxaemia
?neoplasia (especially haemangiosarcoma 血管肉瘤 )
?acute infections (e.g,infectious canine hepatitis)
?haemolytic anaemia
?pancreatitis
?heat stroke,
The clinicopathological features of DIC are,
? Thrombocytopenia
? Increased OSPT/APTT
? Elevated FDPs
? Low fibrinogen
? Schistocytes in the blood film,
DISORDERS OF WHITE CELL NUMBER
兽医临床病理学
College of Veterinary Medicine,SCAU,
Guangzhou,China 510642
Clinical biochemistry
Introduction
Serum proteins
Total protein and albumin
Globulins
Indicators of renal function
Urea nitrogen
Creatinine
Markers of hepatic disease
Alanine aminotransferase
Aspartate aminotransferase
Alkaline phosphatase
Gamma-glutamyi transferase
Bilirubin
Bile acids
Ammonia
Pancreatic disease
Amylase
Lipase
Electrolytes
Sodium; Potassium; Chloride
Magnesium; Calcium; Phosphorus
Muscle enzymes
Creatine kinase
Aspartate aminotransferase
Carbohydrate metabolism
Glucose
Fructosamine
Lipid metabolism
Cholesterol
Triglycerides
Miscellaneous tests
Iron
Lead
Zinc
Copper
Chemical profiles and test selection
SERUM PROTEINS
Total protein and albumin
Physiology
The circulating proteins are synthesized predominantly in the liver,although
plasma cells also contribute to their production,Quantitatively the single most
important protein is albumin (35-50% of the total serum protein concentration).
The other proteins are collectively known as globulins,The functions of proteins
are many and varied but include maintenance of plasma osmotic pressure,
transport of substances around the body (e.g,ferritin铁蛋白,ceruloplasmin血浆
铜蓝蛋白 ),humoral immunity,buffering and enzyme regulation.
Indications for assay
The measurement of proteins is generally included in an initial health screen in all
patients but especially where intestinal,renal or hepatic disease or haemorrhage
is suspected.
Analysis
Protein concentrations can be estimated in serum,plasma,urine or body fluids
with a refractometer or by spectrophotometry,Serum albumin levels are
measured by bromocresol green dye溴甲酚绿 binding and the serum globulin is
calculated by subtraction of the albumin concentration from the total protein
concentration.
Reference ranges
Neonates and very young animals have lower concentrations of albumin and
globulins (due to minimal quantities of immunoglobulins),As the animal gains
immunocompetence the protein concentrations rise to reach adult values.
Physiological decreases in albumin may be noted during pregnancy.
Critical values
Marked hypoalbuminaemia (<15 g/L) is associated with the development of
ascites and tissue oedema,Accumulation of peritoneal fluid may occur at
higher albumin concentrations if there is concurrent portal vein hypertension,
e.g,in chronic liver disease.
Interfering phenomena
Lipaemia,haemolysis and hyperbilirubinaemia produce false increases in total
protein concentrations.
Drug effects
Hormones have a marginal effect on plasma protein concentrations,
Corticosteroids and anabolic steroids may increase the protein concentration
due to their anabolic effects while the catabolic effects of thyroxine can cause a
decrease,
SERUM PROTEINS
Figure 4.3,Causes of hypoalbuminaemia.
Increased loss
Glomerular protein loss
Protein-losing enteropathy
Cutaneous lesions,e.g,bums
External haemorrhage
Decreased production
Hepatic insufficiency
Malnutrition
Maldigestion
Malabsorption
Sequestration
Body cavity effusion
SERUM PROTEINS
Globulins
Analysis
Serum protein electrophoresis (SPE) on cellulose acetate gels
allows fractionation of the proteins,depending
predominantly on their charge and size,After staining for
protein,the cellulose acetate strip is scanned by a
densitometer which converts the relative intensities of the
protein bands to percentages and generates a graph that
demonstrates the protein fractions (albumin,α 1-globulin,
α 2-globulin,β 1-globulin,β 2-globulin,γ -globulin),
Causes of hypoglobulinaemia
The most common pathological causes are haemorrhage and
protein-losing enteropathies,
SERUM PROTEINS
Figure 4.4,Causes of hyperglobulinaemia.
Polyclonal gammopathy
Infections:
Bacterial disease
Viral disease (e.g,FIP)
Immune-mediated diseases:
Systemic lupus erythematosus
Rneumatoid artnntis
Immune-mediated haemolytic anaemia
Immune-mediated thrombocytopema
Neoplasia,especially lymphosarcoma
Monoclonal gammopathy
Neoplasia:
Multiple myeloma
Macroglobulinaemia
Lymphosarcoma
Feline infectious peritonitis (rare)
SERUM PROTEINS
Urea nitrogen
Physiology
★ Dietary proteins are hydrolysed in the intestines to their
constituent amino acids which may,in turn,be degraded
to ammonia by the action of gut bacteria,
★ The ammonia and amino acids are transported to the
liver via the portal circulation where they are utilized in
the urea cycle,
★ The urea formed in the hepatocytes is excreted via the
kidney tubules,
★ Urea plays an important role in concentrating the urine;
the presence of high concentrations of urea and sodium
chloride in the renal medullary interstitium creates an
osmotic gradient for reabsorption of water,
INDICATORS OF RENAL FUNCTION
Indications for assay
The urea nitrogen (urea) concentration is one of the tests used
when screening renal function,It is often measured when
the clinical signs include vomiting,anorexia,weight loss,
polydipsia and dehydration.
Analysis
Urea can be measured in serum,plasma and urine by
spectrophotometry,Stick tests for whole blood are also
available.
Reference ranges
Dogs 3.0-9.0 mmol/L
Cats 5.0-10.0 mmol/L
Interfering phenomena
lipaemia interferes with the analysis and produces variable
effects depending on the methodology.
INDICATORS OF RENAL FUNCTION
Causes of reduced blood urea
☆ Reduced dietary protein intake is associated with a low
blood urea.
☆ In addition,patients with diffuse liver disease have an
impaired capacity to synthesize urea and reduced hepatic
production,Where hepatic disease is suspected,a
complete biochemistry profile and a bile acid stimulation
test are indicated.
☆ The marked diuresis（多尿） associated with some
conditions,especially hyperadrenocorticism and diabetes,
results in increased urinary loss of urea which,in turn,
causes a reduction of the blood urea,
INDICATORS OF RENAL FUNCTION
Causes of increased blood urea
☆ Increased dietary protein intake produces a high level of urea in the blood,
A moderate increase in dietary protein is not commonly associated with a
notable rise in urea above the reference range,but high-protein diets can
cause significant increases,
☆ A 12-hour fast is recommended before sampling for measurement of urea,
☆ Intestinal haemorrhage also results in an increased concentration which is
reported to correlate with the severity of blood loss,
☆ Urea is freely filtered at the glomerulus and reabsorbed in the renal
tubules,The rate of reabsorption is higher at slower urinary flow rates,e.g,
in dehydrated patients,
☆ Blood urea is therefore not a reliable estimate of the glomerular filtration
rate (GFR),Increased urea concentrations are associated with conditions
other than parenchymal renal disease,
☆ The presence of a concentrated urine sample (urine SG > 1.030 in dogs,>
1.035 in cats) supports the diagnosis of a prerenal azotaemia,
INDICATORS OF RENAL FUNCTION
Creatinine
Physiology
◤ Creatinine is formed from creatine in the muscles in an irreversible
reaction,The quantity of creatinine produced depends upon diet (small
contribution) and the muscle mass,Disease affecting the muscle mass may
affect the daily creatinine production.
◤ Both urea and creatinine are freely filtered at the renal glomerulus but
urea is subject to tubular reabsorption and thus creatinine is said to be a
better indicator of GFR.
Analysis
◤ Creatinine can be measured in serum,plasma or abdominal fluid by
spectrophotometric methods.
Reference ranges
Dogs 20-110 umol/L
Cats 40-150umol/L
INDICATORS OF RENAL FUNCTION
Causes of low serum creatinine
◤ Since the daily production of creatinine is dependent upon
the muscle mass of the animal,the body condition should be
considered when interpreting serum creatinine
concentrations,A poor body condition may be associated
with low concentrations while minor rises in such cases may
be more significant than in other individuals.
Causes of increased serum creatinine
◤ Decreased glomerular filtration is the major cause of raised
serum creatinine,However,approximately 75% of nephron
function must be impaired before serum creatinine (and
urea) is increased,Creatinine is considered a more reliable
indicator of GFR than is urea nitrogen,since there are
fewer factors which influence the serum concentration of
creatinine,
INDICATORS OF RENAL FUNCTION
?The biochemical parameters used to assess liver pathology may be divided
into two classes,the hepatic enzymes that reflect liver damage and
cholestasis,and the endogenous indicators of liver function,
? Alanine aminotransferase (ALT) is the most useful enzyme for identifying
hepatocellular damage in dogs and cats but should not be used alone as a
screening test for liver disease,
? The production of other enzymes,i.e,alkaline phosphatase (ALP) and
gamma-glutamyl transferase (GGT),is increased secondary to intra- and
extrahepatic cholestasis,
? These enzymes are markers of cholestatic disease,
? Bilirubin,serum albumin and serum bile acids are considered to be
indicators of hepatic function,
? It is common for extrahepatic disease (e.g,pancreatitis,diabetes mellitus,
hyperadrenocorticism and inflammatory bowel disease) to cause
abnormalities of these biochemical parameters,
MARKERS OF HEPATIC DISEASE
Alanine aminotransferase (ALT)
Physiology
ALT is found in the cytosol of hepatocytes and in muscle tissue in the dog and cat.
Activities in the serum are elevated by leakage of the enzyme secondary to an
increase in hepatocyte membrane permeability or cell necrosis,The former may
simply be a consequence of hypoxia and need not reflect cell death,Increased serum
ALT may be noted within 12 hours of an acute hepatic insult but can take 3-4 days
to reach peak levels after experimental cholestasis（ 胆汁阻塞 ）, The degree of increase
in enzyme activity correlates approximately with the number of hepatocytes affected
but does not indicate the nature,severity or reversibility of the pathological process.
ALT activity is not an indicator of hepatic function.
Indications for assay
Serum ALT is a useful aid in the diagnosis of hepatic disease and is measured where the
clinical signs might suggest a hepatopathy,e.g,weight loss,anorexia,polydipsia,
vomiting,diarrhoea,ascites and jaundice.
Analysis
The activity of the enzyme (in international units) is measured in serum or plasma by
spectrophotometric methods under specified conditions.
Reference ranges
Dogs < 100 units/L
Cats <75 units/L
MARKERS OF HEPATIC DISEASE
Causes of raised ALT activity
Guidelines for the interpretation of raised liver enzyme activities in relation
to liver diseases are given in Chapter liver,The majority of diseases that
affect the liver could potentially cause an increase in serum ALT activity
but those pathological processes that might cause a marked increase
include parenchymal disease/ damage,cholangitis,cholangiohepatitis,
chronic hepatitis,anoxia,cirrhosis and diffuse neoplasia,e.g,lymphoma
(lymphosarcoma),However,in some cases these diseases may be
accompanied by a negligible increase or no increase in serum ALT
activity.
Causes of reduced ALT activity
An artefactual reduction in serum enzyme activities may result from
substrate depletion,Dilution and repeat assay of the sample are necessary
to exclude this phenomenon,Reduced ALT activities (below the reference
range) are generally not considered to be of clinical significance,but the
possibility of chronic liver disease and nutritional deficiencies (zinc or
vitamin B6 ) should be considered.
MARKERS OF HEPATIC DISEASE
Aspartate aminotransferase (AST) (see also Muscle enzymes)
Physiology
AST is located in the mitochondria of the cell and is present in significant quantities
in hepatocytes,erythrocytes and in muscle,AST is therefore not liver-specific but,
like ALT,its activity in the serum is elevated by leakage of the enzyme from the
cell.
Indications for assay
AST is included in diagnostic profiles for investigation of suspected liver disease or
muscle disease.
Analysis
The enzyme activity is measured in serum and heparinized plasma by
spectrophotometry.
Reference ranges Dogs 7-50 units/L Cats 7-60 units/L
Causes of raised AST
The most common causes of increased AST are hepatic disease,muscle disease
(trauma,inflammation) and haemolysis,Concurrent measurement of other
hepatic enzymes (ALT,ALP,GGT) and hepatic function indicators (albumin,
urea,bilirubin,bile acids) are essential to establish the origin of the increased
serum AST and to provide further information regarding liver damage and
function (see Chapter 9),With respect to liver damage,the serum activity of AST
tends to parallel that of ALT,
MARKERS OF HEPATIC DISEASE
Alkaline phosphatase (ALP,SAP)
Physiology
In dogs and cats there are isoforms of ALP located in brush borders in the liver,
placenta,intestine,kidney and bone,In the dog there is also a steroid-induced
isoenzyme (SIALP),the origin of which has not been fully determined,The
production of SIALP is increased by the administration of glucocorticoids (oral,
parenteral or topical),by excessive production of endogenous glucocorticoids
(hyperadrenocorticism) and in association with chronic disease (e.g,renal or
hepatic),The liver isoenzyme is responsible for the serum activity in the normal
adult dog and cat,Indications for assay
Serum ALP is one of the tests commonly included in screening profiles for
hepatic disease (cholestasis) and hyperadrenocorticism,It is therefore useful
where the clinical signs suggest either of these diagnoses,e.g,weight loss,
anorexia,polydipsia,vomiting,diarrhoea,ascites and jaundice.
Analysis
Serum ALP activity is measured in serum or heparinized plasma by
spectrophotometry,Reference ranges
Dogs <200 units/L Cats < 100 units/L
MARKERS OF HEPATIC DISEASE
Causes of raised ALP
From a diagnostic viewpoint the most important isoenzymes in small animals
are the bone,hepatic and steroid-induced forms,Increases in bone ALP
causes raised serum activities in young growing animals,but values are
rarely more than two-fold greater than the upper limit of the adult
reference range,This physiological increase in serum ALP should be
considered.
Increases in the hepatic isoenzyme are commonly associated with
cholestatic disease.
Include pancreatitis,pancreatic neoplasia and cholelithiasis,Choleliths are
very rare in the dog,The enzyme is generally included in profiles where it
contributes to the diagnosis of hepatic disease,ALP should not be used
alone when screeningpatients for evidence of liver disease.
In dogs,the increase in ALP associated with steroid administration varies
dependingon the patient,the drug used and the route of administration.
ALP in the cat has a very short half-life and the magnitude of increase noted
in hepatic disease is generally less than that recorded in dogs,Any
increase in ALP is probably significant in a cat.
MARKERS OF HEPATIC DISEASE
,
Gamma-glutamyl transferase (GGT)
Physiology
GGT is a cytosolic and membrane-bound enzyme found in
highest concentrations in the brush borders of the renal and
bile duct epithelium,Cholestasis and enzyme induction due
to glucocorticoid therapy cause increased serum activities.
Indications for assay
GGT is used in conjunction with ALP and other liver tests
in the diagnosis and monitoring of hepatic disease,It is
thought to be more useful than ALP in the cat and the
serum activity in dogs does not appear to be affected by the
administration of anticonvulsants,
Dogs 0-8.0 units/L Cats 0-8.0 units/L
Causes of increased GGT
Serum GGT is a marker for cholestatic disease in the dog
and cat, In the cat it may be more useful than ALP in the
diagnosis of cholestatic hepatic disease
MARKERS OF HEPATIC DISEASE
Bilirubin
Physiology
Bilirubin（胆红素） is derived from the catabolism of haemoproteins in
the cells of the reticuloendothelial system,The newly formed lipid-soluble
bilirubin (indirect-reacting bilirubin) is then bound to albumin,which
facilitates its transfer through the aqueous phase of the plasma to the
liver,In the hepatocyte the bilirubin is conjugated with glucuronic acid
（葡糖醛酸）,creating a water-soluble molecule (direct-reacting
bilirubin),
Indications for assay
Measurement of bilirubin is indicated where there is jaundice（黄疸）
on clinical examination,visible icterus（黄疸） of the serum or plasma,
or suspected hepatic disease,Clinical jaundice in the dog is detected when
the bilirubin is at least 25-35 umol/L,
Analysis
The total serum bilirubin concentration (conjugated and unconjugated) is
measured in serum or plasma by spectrophotometry,
Reference ranges
Dogs 0-6.8 umol/L Cats 0-6.8 umol/L
MARKERS OF HEPATIC DISEASE
Causes of hyperbilirubinaemia
Jaundice may be classified according to the underlying pathological process:
?prehepatic jaundice (increased production of bilirubin,e.g,haemolytic anaemia,
and internal haemorrhage);
?hepatic jaundice (failure of uptake or conjugation of bilirubin);
?posthepatic jaundice (obstruction of the biliary system),
A full haematological profile is indicated in all jaundiced patients to exclude the
possibility of prehepatic causes,Characteristic findings that may be noted in
haemolytic anaemia include marked reticulocytosis (网状细胞过多症,indicative
oferythrocyte regeneration),autoagglutination of the red cells and the formation of
spherocytes,The platelet count and serum proteins are commonly within the
reference range for the species,The abnormalities of bilirubin associated with
hepatic disease and cholestatic disease are discussed more fully,
Previously it was believed that the measurement of direct and indirect-reacting
bilirubin would help to determine the cause of the jaundice,However,it is now
clear that this is not the case in the dog and cat and that hepatic,haemolytic and
biliary tract diseases produce variable increases in these fractions,Differentiation
of prehepatic,hepatic and posthepatic jaundice requires a full haematological and
biochemical investigation (including measurement of red cell mass,examination of
a blood smear and liver function tests) and may require examination of the biliary
tract,Hepatic biopsy may also be necessary in some cases,
MARKERS OF HEPATIC DISEASE
Bile acids
Physiology
The primary bile acids are produced in the liver from cholesterol and are then
conjugated to taurine（ 氨基乙磺酸 ） or glycine（ 氨基乙酸 ）, They are excreted into
the biliary tree and stored in the gallbladder,Gallbladder contraction
(stimulated by ingestion of food) releases the bile acids into the intestines where
they facilitate the digestion and absorption of dietary lipid,The bile acids are
efficiently reabsorbed in the ileum,resulting in very small faecal loss,The total
pool of bile acids may undergo enterohepatic circulation two to five times
during a single meal.
Indications for assay
Inclusion of bile acids in a profile is indicated where there is suspicion of
hepatic disease,Clinical signs in such patients might include hepatomegaly（ 肝
大 ）,microhepatica（ 小肝 ） and abnormal central nervous system signs,The
sensitivity of the bile acid assay may be increased by using a bile acid
stimulation test.
Reference ranges (fasted)
Dogs 0-15 umol/L
Cats 0-15 umol/L
MARKERS OF HEPATIC DISEASE
Causes of increased bile acids
The fasting serum bile acid concentration may be raised in association
with primary or secondary hepatic disease,The assay facilitates
identification of hepatic dysfunction but gives no indication as to the
nature or reversibility of the liver pathology,Values exceeding
30umol/L are commonly associated with histological lesions and biopsy
may be helpful in these cases,It is important to remember that the
histological changes could still be associated with secondary hepatic
disease even though the fasting bile acid concentration is >30 umol/L,
for example in hyperadrenocorticism.
The use of the bile acid stimulation test may improve the sensitivity of
testing,For this,serum bile acid concentrations are measured in a
sample collected after a 12-hour fast (fasting bile acid concentration)
and 2 hours after a fatty meal (postprandial（餐后） bile acid
concentration),In one study of 108 cats,the postprandial bile acid
concentration was found to have the highest sensitivity of any single
test for the diagnosis of feline liver disease,
MARKERS OF HEPATIC DISEASE
Ammonia
Physiology
Dietary proteins are hydrolysed in the gut to amino acids which,in turn,may be
degraded by intestinal bacteria,producing ammonia,Ammonia is transported
to the liver where it is used as a precursor in the synthesis of urea,Increased
blood ammonia concentrations are observed in some patients with diffuse liver
disease (with a reduced capacity for urea synthesis) and in individuals with
portosystemic shunts.
Indications for assay
Ammonia is used in the evaluation of hepatic function; the indications for
measurement are the same as for bile acids.
Analysis
Ammonia is measured in blood,serum or plasma by dry reagent and enzymatic
methods,Samples should be collected into a chilled sample tube and stored on
ice until analysis,which must be carried out within 20 minutes of collection.
Reference ranges
Dogs 0-60 umol/L
Cats 0-60 umol/L
MARKERS OF HEPATIC DISEASE
Causes of increased ammonia
Increased ammonia concentrations are associated with feeding high-
protein diets and with intestinal haemorrhage (due to the
increased delivery of amino acids to the intestinal bacteria).
Diffuse hepatic disease,resulting in the failure of conversion of
ammonia to urea,and portosystemic shunts (congenital and
acquired) will also produce increased serum ammonia
concentrations.
MARKERS OF HEPATIC DISEASE
PANCREATIC DISEASE
Amylase
Physiology
Amylase（ 淀粉酶 ） is a calcium-dependent enzyme,produced by the
pancreatic acinar cells,which hydrolyses complex carbohydrates,The
enzyme passes directly from the pancreas into the circulation where it
is filtered by the renal tubules; the inactivated enzyme is reabsorbed
by the tubular epithelium,Amylase activity in the tissues of the dog
and cat is highest in the pancreas but is also found in the intestines
and liver.
Indications for assay
Amylase should be measured when the presenting signs might suggest
pancreatitis（ 胰腺炎 ）,e.g,vomiting,abdominal pain or icterus,or
when there is free peritoneal fluid.
Analysis
Amylase activities may be measured in serum,heparinized plasma and
abdominal fluid using spectrophotometric methods.
Reference ranges
Dogs 400-2000units/L Cats 400-2000units/L
Causes of increased amylase
The tissue distribution of amylase is not restricted to the pancreas and
therefore raised serum activities are not specific for pancreatitis.
Reduced glomerular filtration (prerenal,renal,postrenal) is often associated
with an increased serum amylase activity but this is commonly less than two
to three times greater than the upper limit of the reference range.
Serum activities above this level are suggestive of pancreatitis but the degree of
increase does not correlate well with the severity of pancreatitis.
If an azotaemic（ 氮血症 ） patient has an amylase activity two to three times the
upper limit of the reference range then pancreatic disease must be
considered,The simultaneous measurement of amylase and lipase in cases
of suspected pancreatitis is advisable while additional tests of renal and
hepatic function should also be included in the biochemical profile.
Amylase is not a reliable indicatorof pancreatitis in cats,
In cases that present with free peritoneal fluid,full analysis of the fluid (protein
concentration,cell counts and cytological examination) and measurement of
the serum and fluid amylase activities may be useful,The presence of a non-
septic exudate with greater amylase activity than the serum may be
associated with pancreatitis or bowel rupture,
PANCREATIC DISEASE
Lipase
Physiology
Lipase is a digestive enzyme,produced by the pancreatic acinar cells,that
hydrolyses triglycerides,The enzyme is cleared from the circulation by
renal inactivation,As with amylase,lipase may originate from pancreatic
or extrapancreatic sources,Pancreatic damage and inflammation results
in the release of lipase into the surrounding gland and peritoneal tissue
which may cause the development of necrosis in the peripancreatic
peritoneal fat.
Indications for assay
Indications for the measurement of lipase are the same as for amylase.
Amylase and lipase assays should be performed simultaneously in cases in
which pancreatitis is suspected,but the increases in enzyme activities are
often not parallel (marked increases in one enzyme may be associated with
minimal increases in the other),Analysis
Lipase activities are measured in serum,heparinized plasma and body fluids
using turbidimetric methods.
Reference ranges
Dogs 0-500 units/L Cats 0-700 units/L
PANCREATIC DISEASE
Causes of raised serum lipase
Since lipase originates from both pancreatic and
extrapancreatic tissue,an increase in serum activity is not
diagnostic of pancreatitis,Increased serum activity is also
noted in azotaemic patients,although the values generally do
not exceed two to three times the upper limit of the reference
range.
In addition,moderate elevations of lipase (up to 5-fold
increases) have been reported in association with
administration of dexamethasone without evidence of
histological changes in the pancreas,A normal lipase activity
does not preclude pancreatic disease.
Lipase has been reported to be persistently elevated in cats
with experimentally induced pancreatitis but this is not a
consistent finding in naturally occurring disease,
PANCREATIC DISEASE
CARBOHYDRATE METABOLISM
Physiology
Glucose is the principal source of energy for mammalian tissues and is derived from the
diet and hepatic gluconeogenesis,The blood concentration is controlled by
hormones which regulate its entry into,and removal from,the circulation (insulin,
glucagon,adrenaline,cortisol),In the kidney of the dog and cat,glucose entering the
glomerular ultrafiltrate is reabsorbed by the renal tubules.
However,the renal reabsorption of glucose is overwhelmed in the presence of blood
glucose concentrations greater than 10-12 mmol/1,resulting in glucosuria.
Indications for assay
Measurement of blood glucose is essential where presenting clinical signs could suggest,
diabetes mellitus (polydipsia,polyuria,weight loss,cataract formation),
diabetic ketoacidosis (vomiting,diarrhoea,anorexia)
hypoglycaemia (weakness,collapse,seizures,disorientation,depression,blindness).
In addition,the assay is included in general health screens where it may provide
supportive evidence for other disease processes (hyperadrenocorticism,hepatic
disease),Measurement of the blood glucose concentration is the ideal method of
monitoring the stabilization of diabetic patients on insulin therapy and allows
optimization of the therapeutic regimen,In such cases,glucose is measured in
samples collected at 2-hourly intervals,allowing calculation of the duration of action
and peak time of action of the administered insulin,
Glucose
Analysis
Reagent strips,Rapid-analysis reagent strips require the use of whole blood
with no anticoagulant.
Laboratory analysis,Spectrophotometric methods (enzymatic or chemical)
arc generally used for the measurement of blood glucose,Where in-house
equipment demands the use of heparinized plasma,the sample must be
separated immediately after collection,This prevents depletion of the
plasma glucose by the erythrocytes,Collection of the blood into fluoride
oxalate is the preferred method of preventing erythrocyte glucose
utilization when a delay in analysis is anticipated,such as during
transport to a commercial laboratory.
Reference ranges
Dogs 3.5-5.5 mmol/L
Cats 3.5-6.5 mmol/L
Glucose
Causes of hypoglycaemia
Marked hypoglycaemia (glucose <2 mmol/L) most
commonly results from overproduction of insulin or
excessive utilization of glucose by neoplastic cells,
Insulin-secreting tumours of the pancreas (insulinomas)
produce biologically active hormone which increases
the uptake of glucose by the body tissues and impairs
hepatic gluconeogenesis,resulting in hypoglycaemia,
In one study of dogs with insulinomas the mean (+SD)
plasma glucose concentration was 2.14(± 0.82) mmol/1,
Extrapancrcatic tumours occasionally cause
hypoglycaemia by secretion of an insulin-like substance
or by increased utilization of plasma glucose,
Glucose
Neoplastic:
Insulin-secreting tumour of the pancreas
(insulinoma)
Hepatocellular carcinoma
Endocrine:
Hypoadrenocorticism
Hepatic insufficiency:
Congenital vascularshunts
Acquired vascular shunts
Chronic hepatic fibrosis (cirrhosis)
Hepatic necrosis (e.g,hepatotoxins,
bacterial infection,trauma)
Glucose
Figure 4.19,Causes of hypoglycaemia in the dog,
Cats may rarely be affected by insulinoma.
Substrate deficiency:
Neonatal hypoglycaemia
Juvenile hypoglycaemia
Hunting dog hypoglycaemia
Glycogen storage disease
Sepsis
Causes of hyperglycaemia
Hyperglycaemia commonly results from a relative or absolute lack of
insulin,This leads to impaired tissue utilization of plasma glucose and
an increase in the rate of gluconeogenesis.
Mild hyperglycaemia (6.7-10 mmol/L) in the dog may be noted as part
of an adrenaline stress response or secondary to excessive secretion or
administration of other diabetogenic hormones,in particular
glucocorticoids and progesterone,The mild hyperglycaemia is a result
of the hormonal antagonism of the actions of insulin,In addition,mild
hyperglycaemia may be noted in the postprandial period in dogs fed a
sugar-rich diet such as semi-moist foods.
A persistent,moderate to marked hyperglycaemia in the dog is
consistent with diabetes mellitus,Such cases do not present with
clinical signs (polyuria and polydipsia) until the renal threshold for
glucose is exceeded,resulting in osmotic diuresis.
In the cat,an adrenaline-induced stress response may produce a
moderate or marked increase in glucose concentration,The diagnosis
of diabetes mellitus is often difficult in cats and confirmation requires
documentation of persistent hyperglycaemia with compatible clinical
signs.
Glucose
Figure 4.20,Causes of hyperglycaemia.
Adrenaline stress response (especially marked in cats)
Postprandial
Diabetes mellitus
Hyperadrenocorticism (dogs and rarely cats)
Acromegaly (cats)
Acute pancreatitis (dogs and cats)
Renal insufficiency
Glucose
Fructosamine
Physiology
Fructosamine is a glycated serum protein which is formed by the non-
enzymatic reaction between a sugar and an amino acid,The total amount
of fructosamine formed is proportional to the serum glucose
concentration during the lifespan of the proteins,In dogs and cats,
fructosamine has been found to be a useful parameter in the diagnosis
and management of diabetes mellitus.
Indications for assay
Serum fructosamine concentrations are useful in the diagnosis of diabetes
mellitus and in identifying persistent hyperglycaemia during therapy.
Measurement of fructosamine may also be helpful in confirming the
presence of persistent hypoglycaemia.
Analysis
Fructosamine is measured using a method based on the reducing ability of
fructosamine in alkaline solution.
Reference ranges
Dogs 250-350 umol/L
Cats 150-270 umol/L
Causes of low serum fructosamine
A low serum fructosamine concentration has been recorded in a dog with
an insulin-secreting tumour of the pancreas (insulinoma),It has been
suggested that the measurement of serum fructosamine in addition to
glucose and insulin may be helpful in confirming the presence of
insulinomas.
Causes of raised fructosamine
Raised serum concentrations of fructosamine reflect persistent
hyperglycaemia over the preceding 2-3 weeks,In dogs with diabetes the
serum fructosamine concentration is significantly greater than in dogs
with other diseases,Fructosamine is also useful for confirming diabetes
mellitus in the cat and can be helpful in identifying persistent
hyperglycaemia after initial stabilization on insulin therapy.
Fructosamine
LIPID METABOLISM
Physiology
?Cholesterol is the most common steroid in the body tissues and acts as a
precursor compound for steroid hormone and bile salt synthesis.
?The majority of the body's cholesterol is synthesized by the liver,but
the remainder originates from dietary sources,Excess cholesterol is
excreted in the bile.
Indications for assay
?Hypercholesterolaemia is often associated with endocrine disease in the
dog and cat and is frequently measured as part of a general health
profile in these species,
?Raised plasma cholesterol alone is not commonly responsible for the
development of clinical disease in the dog and cat,However,marked
hypercholesterolaemia and hypertriglyceridaemia secondary to thyroid
dysfunction in dogs have been associated with the development of
peripheral vascular disease,
?Analysis Cholesterol concentrations are assayed in serum,heparinized
plasma or EDTA plasma using spectrophotometric,automated direct
and enzymatic methods,
Cholesterol
Figure 4 Causes of alterations in plasma cholesterol concentrations,
Hypocholesterolaemia
Protein-losing enteropathy
Maldigestion/malabsorption
Hepatopathy (portocaval shunt,cirrhosis)
Hypercholesterolaemia
Postprandial hyperlipidaemia
Secondary hyperlipidaemia:
Hypothyroidism
Diabetes mellitus
Hyperadrenocorticism
Cholestatic disease
Nephrotic syndrome
Causes of hypercholesterolaemia
A marginal increase in the cholesterol concentration may be noted in
samples collected in the postprandial period versus a fasted sample,This
increased level generally does not exceed the reference range for the
species.
Hypercholesterolaemia in the dog and cat is most commonly associated
with endocrine disease (diabetes mellitus,hypothyroidism,
hyperadrenocorticism),In each of these endocrine disorders there may
be a concurrent increase in serum triglyceride concentration.
Hypercholesterolaemia may also be noted in cholestatic disease and
glomerulonephritis(肾小球性肾炎 ）,
Further specialist investigation (e.g,lipoprotein electrophoresis) may be
necessary if no underlying systemic or endocrine disease can be
identified and the hypercholesterolaemia is marked and persistent.
Triglycerides
Physiology
The triglycerides are the most abundant lipids in the body and their
storage in adipose tissue provides an essential reserve of chemical
energy for tissue requirements,They are derived from the diet and also
synthesized de novo （ 重新 ） in the liver.
Indications for assay
Fasting hypertriglyceridaemia in the dog and cat is a pathological finding,
The presence of large triglyceride-rich lipoproteins imparts a turbidity
to the plasma or serum (lipaemia),Triglycerides should therefore be
measured in all fasting blood samples that appear to be lipaemic,
Clinical manifestations of hypertriglyceridaemia
include,recurrent abdominal pain,alimentary signs,seizures,
Causes of hypotriglyceridaemia
Hypotriglyceridaemia has not been consistently associated with any
specific disease process although it has been reported in several cases
of acute and chronic hepatic disease.
Causes of hypertriglyceridaemia
The most common cause of apparent hypertriglyceridaemia in the dog
and cat is a failure to obtain a fasting sample (postprandial
hyperlipidaemia),If hypertriglyceridaemia is documented in a sample
collected after a 12-hour fast,endocrine and systemic disease should be
excluded (diabetes mellitus,hypothyroidism,hyperadrencorticism,
glomerulonephritis),Many dogs with spontaneous acute pancreatitis
have increased serum triglyceride concentrations,The relationship
between pancreatitis and hyperlipidaemia has not been fully elucidated
but it appears that the increased triglyceride concentration may
predispose patients to pancreatic pathology.
Figure 5 Causes of hypertriglyceridaemia
in the dog and cat
Postprandial hyperlipidaemia
Secondary hyperlipidaemia:
Hypothyroidism
Diabetes mellitus
Hyperadrenocorticism
Acute pancreatitis
Primary hyperlipidaemia:
Idiopathic hyperchylomicronaemia of the Miniature Schnauzer
Familial hyperchylomicronaemia（ 乳糜微粒血症 ） in the cat
Idiopathic hypertriglyceridaemia
CHEMICAL PROFILES AND TEST SELECTION
? On the initial presentation of an ill patient,a clinician formulates a list of
differential diagnoses based on the history and clinical findings.
? Where the clinical findings are specific,e.g,pallor of the mucous
membranes suggestive of anaemia,then steps are taken to confirm this
suspicion and to elucidate the possible cause.
? A wider,more comprehensive investigation is necessary when clinical
signs may be caused by many metabolic disorders; for example,
polydipsia in the dog could be the result of endocrine disease,renal
disease or hepatic disease.
? The selection of tests depends upon the differential diagnoses,the range
of conditions that must be excluded,the availability of the tests,and the
cost of tests,In the case of the polydipsic dog,a cost-effective profile is
required to cover the possibility of organ failure (renal,hepatic),
endocrine disease (diabetes mellitus,hyperadrenocorticism) and
hypercalcaemia.
?Some of these differentials may be excluded or confirmed on
the basis of individual tests (e.g,urea and creatinine for
renal disease) but inclusion in a more comprehensive profile
allows the simultaneous assessment and cost-effective
exclusion of many other causes of polydipsia.
?When the clinical signs are vague and a 'general health
screen' is required,then it is necessary to select a broad
range of analytes which will reflect a number of common
diseases or pathological states,The inclusion of tests that
are not organ-specific but which provide general
information regarding the hydration and essential
homeostatic mechanisms is worthwhile,e.g,total proteins,
albumin,electrolytes,glucose.
CHEMICAL PROFILES AND TEST SELECTION
Profile
Health
Pre-
anaesthetic
screen*
Extended*
health
screen
Polydipsia
profile
Seizure
profile
Renal profile
Hepatic
profile
Tests
FBC,TP,albumin,globulin,ALT,ALP,GGT,bilirubin,
amylase,urea,creatinine,glucose,urinalysis
FBC,TP,albumin,globulin,ALT,ALP,bilirubin,urea,
creatinine,glucose
As health screen plus bile acids,electrolytes,cholesterol,
CK,calcium,phosphorus
FBC,TP,albumin,globulin,ALT,ALP,bilirubin,bile acids,
CK,cholesterol,urea,creatinine,glucose,calcium,
phosphorus,electrolyte screen,urinalysis (SG,dipstick
and sediment examination).
FBC,TP,albumin,globulin,ALT,ALP,bile acids,urea,
creatinine,glucose,calcium,CK,phosphorus,magnesium,
electrolyte screen
PCV,TP,albumin,globulin,urea,creatinine,sodium,
potassium,calcium,phosphorus,urinalysis (SG dipstick
and sediment examination)
TP,albumin,globulin,ALT,ALP,AST,GGT,bilirubin,
bile acids,cholesterol
Indications
Routine
screening
Screen for existing
disease prior to
routine surgery
Gastrointestinai.end
ocrine disease and
nonlocalizing signs
Polydipsia
Seizures,weakness,
episodic collapse
Monitoring
hepatotoxicity
Gastrointestinal System
Fecal analysis
Examination of vomitus
Blood tests
Imaging techniques
Endoscopy
Dysphagia and regurgitation
?Collect a history and conduct a thorough physical examination
?Complete a neurological examination
?Observe the patient eating,to assess the likely stage of the
swallowing process affected
?Plain radiography of pharynx and oesophagus
?Possible contrast studies - barium swallow and fluoroscopy
?Examination of oral cavity and pharynx under general
anaesthesia
?Endoscopic examination of pharynx and oesophagus
Possible diagnostic procedures for common alimentary symptoms
Vomiting
* Collect a history and conduct a thorough physical examination
* Characterize the vomitus produced
* Is the vomiting primary or secondary?
PRIMARY SECONDARY
Haematology and biochemistry Haematology
and biochemistry
Plain radiography Urinalysis
Contrast studies Specific tests of
Endoscopy/ exploratory organ function
laparotomy
Possible diagnostic procedures for common alimentary symptoms
Diarrhoea
? Collect a history and conduct a thorough physical examination
? Physical examination of the faeces produced
? Is the diarrhoea primary or secondary?
? If primary,is the diarrhoea of small or large intestinal origin?
PRIMARY SECONDARY
Small intestinal Large intestinal Urinalysis
Haematology/biochemistry Faecal culture Specific tests of organ function
Faecal culture Worm egg count
Worm egg count Rectal examination
Undigested food analysis Plain radiography
Serum folate/cobalamin Endoscopy/biopsy
Trypsin-like immunoreactivity
Breath hydrogen assay
Sugar permeability test
Ultrasound scan
Endoscopy/exploratory laparotomy
Possible diagnostic procedures for common alimentary symptoms
Constipation
* Collect a history and conduct a thorough physical
examination
* Rectal examination
* Neurological examination
* Orthopaedic assessment
* Plain radiography
Possible diagnostic procedures for common alimentary symptoms
Faecal tenesmus(里急后重 ）
?Collect a history and conduct a thorough
physical examination
?Rectal examination
?Faecal culture and worm egg count
?Plain radiography
?Contrast studies
?Ultrasound scan
?Endoscopy/biopsy
Possible diagnostic procedures for common alimentary symptoms
Acute abdomen
?Collect a history and conduct a thorough
physical examination
?Careful abdominal palpation
?Haematology and biochemistry
?Plain radiography
?Possibly contrast studies
?Paracentesis
?Ultrasound scan
? Exploratory laparotomy
Possible diagnostic procedures for common alimentary symptoms
Abdominal enlargement
?Collect a history and conduct a thorough
physical examination
?Careful abdominal palpation
?Haematology and biochemistry
?Plain radiography
?Paracentesis（ 腹腔穿刺 ）
?Ultrasound scan
?Exploratory laparotomy
Possible diagnostic procedures for common alimentary symptoms
FAECAL ANALYSIS
Physical appearance
Initial examination of a fresh fecal sample should concentrate on its physical
appearance,In many cases of diarrhoea it is possible to decide whether it is
associated with a small or large intestinal problem using the criteria shown in
Table 8.1.
Such a differentiation not only gives the clinician valuable information regarding
the location of the lesion but consequently assists in the selection of further
appropriate diagnostic tests.
Unfortunately,not all diarrhoeas may be readily classified,and features of both
small and large intestinal disease may be present,This may reflect a small
intestinal problem which results in the abnormal presence of nutrients or other
agents in the large intestine,thereby causing signs of large intestinal disease.
Alternatively,it may reflect a condition that affects both the small and the large
intestine equally.
Table 8.1:Characteristics of faeces passed in small
and large intestinal diarrhoea.
Symptom/Sign Small intestine Large intestine
Faecal volume Increased Reduced
Faecal tenesmus None Present
Faecal blood None or changed Often present
Faecal mucus None Often present
Urgency（ 尿急 ） Rare Often present
Dyschezia（ 排便困难 ） Absent Often present
Steatorrhoea（ 脂肪痢 ） Often present Absent
Vomiting May occur Occurs in 30% of cases
Weight loss Present Absent
Flatus/borborygmi(肠鸣 ) Present Rare
Coat/skincondition Poor Normal
Appetite Increased Normal or reduced
Figure 8.2 Major causes of acute diarrhoea
in dogs and cats.
Endoparasitism:
Hookworms钩虫
Whipworms鞭虫
Giardiasis贾第鞭毛虫病
Dietary indiscretions:
Soiled foods
Scavenging
Over-eating
Viral infections:
Feline panleucopenia猫瘟
Canine parvovirus犬细小病毒
Coronavirus冠状病毒
Bacterial infection:
Salmonellosis
Campylobacter infection弯曲菌
Intussusception肠套叠
Haemorrhagic gastroenteritis
Figure 8.3:Major cause of chronic diarrhoea
in dogs and cats,
Small intestinal disease:
Lymphocytic-plasmacytic
enteritis淋巴细胞 -浆细胞性肠炎
Eosinophilic enteritis
Lymphangiectasia淋巴管扩张
Lymphosarcoma淋巴肉瘤
Giardiasis
Exocrine pancreatic
insufficiency (EPI)
Colitis:
Lymphocytic-plasmacytic
Eosinophilic
Histiocytic
Granulomatous
Lymphosarcoma
Systemic disease:
Hyperthyroidism (cats)
Hypoadrenocorticalism
Hypothyroidism (dogs)
Chronic renal failure
Hepatic disease
FeLV,FIV and FIP
Melaena（ 黑粪症 ） can be defined as the presence of changed blood in
the faeces,The appearance of melaena will depend on the extent of
bleeding and its location,but malaenic faeces normally appear black and
tarry in consistency,This appearance is normally associated with
bleeding into the small intestine,although melaena may originate from
the stomach or from the oesophagus,pharynx,mouth or respiratory
system,In the latter cases blood is swallowed and passes through the
alimentary tract to appear as melaena,giving the impression of
alimentary disease,Patients with clotting disorders may present with
melaena,but again careful clinical examination should reveal bleeding
from other locations,confirming a generalized disorder.
Occult blood（ 潜血 ） refers to the presence of microscopic amounts of
blood that can only be detected by laboratory analysis,Great care is
required in interpreting a positive result in dogs and cats as they are
often fed meat-based diets,The presence of haemoglobin or myoglobin in
the diet will give false positive results,It is therefore important to place
the patient on a meat-free diet for a minimum of 3 days prior to testing
for occult blood,A true strong positive result indicates only that bleeding
is occurring somewhere along the alimentary tract.
Culture for bacteria
Normal flora
The small intestine lies between the almost sterile stomach
(due to gastric acid) and the large bacterial population
located in the colon,Bacterial numbers in the proximal small
intestine are low but numbers increase in the ileum,The
actual numbers present in any individual will vary
depending on various internal and external factors,
Many of the 'normal' flora are beneficial to the animal by
producing vitamin K,biotin,folate and short-chain fatty
acids (SCFAs),If the numbers of bacteria present in the
small intestine increase,small intestinal bacterial
overgrowth (SIBO) develops,Such a proliferation of
bacteria can seriously damage the intestinal mucosa,The
point at which bacterial populations induce clinical signs of
SIBO will vary with each individual and the genus of
bacteria present,
Pathogenic bacteria
Pathogenic bacteria may establish when there is interference with the
normal physiological regulation of the resident flora,Bacterial
properties that permit pathogens to establish include,the presence of
flagellae; production of enzymes such as proteases; the ability of
bacteria to adhere to the mucosa; and production of factors that
interfere with intestinal motility,The abilities to produce enterotoxin
and to invade enterocytes significantlyincrease pathogenicity.
Potential pathogens include Salmonella,Campylobacter,Yersinia
and Clostridium species and Escherichia coli.
Analysis for viruses
Canine parvovirus (CPV-2) infection usually results in an acute
enteritis with secondary bacterial infection,involving
especially Salmonella and Campylobacter spp,A definitive
diagnosis of parvovirus infection requires collection of a fresh
faecal sample for viral antigen detection,Ideally,samples
should be collected within the first 2 days of infection when
the largest number of virus particles are present,A commercial
ELISA test kit is available for the detection of parvovirus
antigen in faeces,Serology can also be carried out in order to
detect a rising titre of antibody indicating recent parvovirus
infection,
Endoparasites
Endoparasitic infection with roundworms
(Toxocara canis Toxocara cati,Toxascaris
leonina) and tapeworms (Dipylidium caninum,
Taenia spp.and Echmococcus) are,in the
author's experience,very rare causes of
diarrhoea in dogs and cats,However,
Echinococcus and Toxocara both carry a
significant public health risk and should be
identified and treated whenever possible,
Faecal smears
Fresh faecal smears provide a quick and cheap method
of examining faecal samples,However,as there is no
concentration of ova it is easy to miss parasite eggs or
cysts that are present in small numbers,A fresh fecal
sample should be mixed with a small volume of
physiological saline on a microscope slide,If
protozoans are suspected,one drop of Lugol's iodine
will highlight these parasites but will reduce their
motility,A negative result may be accurate or may
reflect the small numbers of parasitic eggs present,
intermittent excretion,or the effects of agents such as
barium sulphate,kaolin,pectin or enemas.
Faecal flotation
Faecal flotation is a more sensitive method than the faecal
smear for the detection of parasite eggs and cysl
because the technique concentrates their numbers in a
small volume of solution,Several methods have bee
developed,but for the purposes of this chapter on two
methods will be described,Faecal samples for
detection of parasite eggs or cysts may be preserved b
refrigeration at +4C for up to 2 days prior to
examination,but should not be frozen,Preservation of
faecal samples may also be carried out using 1 part
faecel 3 parts preservative (1.5 g sodium acetate,2 ml
glacial acetic acid,4 ml 40% formalin plus 92.5 ml
water).
Hepatobiliary System
Introduction
Diseases of the liver frequently present the small animal clinician with a
diagnostic challenge; signs are often varied and vague and,despite a
wide array of diagnostic tests of both hepatic damage and function,
there is rarely a single test that identifies the problem definitively,For
example,jaundice is often considered a cardinal sign of liver disease,
yet can be caused by non-hepatic conditions (e.g,haemolysis,
extrahepatic bile duct obstruction) as well as a range of different liver
diseases,Conversely,significant liver disease can exist in the absence of
jaundice,Nevertheless,following a thorough history-taking and careful
physical examination,astute interpretation of a panel of laboratory
tests in conjunction with radiographic and ultrasonographic imaging
of the hepatobiliary system will often permit a presumptive diagnosis
to be made,In most cases,however,with the exception of congenital
portosystemic shunts (PSS),definitive diagnosis of primary liver
disease will require histopathological examination of liver tissue,
Figure 9.1,Some of the more common extrahepatic
disorders that can cause abnormal liver test results,
Acute pancreatitis
Diabetes mellitus
Exocrine pancreatic insufficiency
Extrahepatic bacterial infection
Hyperadrenocortisolism
Hyperthyroidism
Hypoadrenocorticism
Hypothyroidism
Immune-mediated haemolytic anaemia
Inflammatory bowel disease
Protein-losing enteropathy
Right-sided heart failure
Septicaemia
Shock
Table 9.1:Clinicopathological abnormalities associated with disturbances
of hepatobiliary function,
Function Abnormal laboratory test resultassociated with liver
dysfunction
Carbohydrate metabolism:
Glucose homeostasis
Hyper- or hypoglycaemia
Lipid metabolism:
Cholesterol
Fatty acids
Lipoproteins
Bile acids
Hypo- or hypercholesterolaemia
Hypertriglyceridaemia
Lipaemia
Elevated bile acids
Protein metabolism:
Albumin
Globulins
Coagulation proteins
Hypoalbuminaemia
Increased acute phase proteins,immunoglobulins
Coagulopathies
Vitamin metabolism? Decreased folate,cobalamin
Vitamin E,vitamin K may be reduced depending on the
disease
Immunological functions Hyperglobulinaemia
Increased acute phase proteins
Detoxification Hyperammonaemia
Decreased urea
Hyperbilimbinaemia
CLINICOPATHOLOGICAL CHANGES IN LIVER DISEASE
Consequences of hepatobiliary dysfunction
The diverse functions of the hepatobiliary system are reflected in the
diverse clinicopathological changes that can be found in liver disease
(Figure 9.3),The defective metabolism and excretion of bilirubin,
causing accumulation of circulating bilirubin and the development of
jaundice,is often considered the hallmark of liver disease,but it is only
one of many abnormal laboratory tests that may found in liver disease,
Indeed,even hyperbilirubinaemia from biliary obstruction is usually
associated with hypercholesterolaemia and elevations of cholestatic
marker enzymes,
Figure 9.3,Clinical signs of hepatobiliary disease,
Depression,decreased appetite and lethargy
Stunting and weight loss
Vomiting,diarrhoea,and grey acholic faeces
Polydipsia and polyuria
Ascites
Icterus
Altered liver size
Bleeding tendency
Abdominal pain (rare)
Encephalopathy(脑病 )
Correlation with clinical signs
The clinical signs of liver disease are many and varied (Figure 9.3)
and may be related to specific laboratory abnormalities,Signs are
often vague and not apparent until there is significant hepatic
dysfunction,which is why laboratory testing is helpful in detecting
and characterizing early liver disease,However,it must always be
remembered that equally abnormal tests may be secondary to a
primary systemic disease,For example,fatty infiltration of the
liver in diabetes mellitus can cause increases in serum activities of
liver specific enzymes in both dogs and cats,and can result in
jaundice in cats,
Depression and diminished appetite
These signs are reflections of disturbed metabolism in liver disease,but
are not associated with specific laboratory test abnormalities,Anaemia
of chronic disease may be present,Abnormal lipoprotein and
cholesterol metabolism may occur,Hypoglycaemia is seen in end-stage
disease and may be one of many factors producing the signs of liver
failure usually attributed to accumulation of metabolic toxins,
Stunting and weight loss
Congenital PSS and juvenile hepatopathies are associated with stunting,
but the biochemical disturbances responsible are multifarious,
Hypoproteinaemia is often associated with muscle wasting,
Gastrointestinal signs
Grey,acholic faeces are seen in biliary obstruction,and are therefore
associated with jaundice,Diarrhoea may be a reflection of
hypoproteinaemia causing bowel oedema,although lack of luminal bile
salts and portal hypertension are more likely causes,
Polydipsia and polyuria
These signs may be associated with low levels of serum urea,although
other mechanisms,e.g,hypercortisolism,are involved in their
pathogenesis,
Ascites
Hypoproteinaemia is a recognized cause of tissue fluid accumulation,
However,ascites is more common than generalized oedema in liver
disease,suggesting portal hypertension in acquired liver disease is
also an important factor.
Icterus
Hyperbilirubinaemia causes jaundice,and may be due to prehepatic
(haemolysis) or posthepatic (biliary obstruction,biliary leakage)
disease as well as primary intrahepatic causes,
Liver size
Diseases causing altered liver size are listed in Figure 9.4,but there
are no specific laboratory markers of liver size and many diseases
are not associated with abnormal liver size,Lipaemia may
correlate with fatty infiltration of the liver,
Bleeding tendency
Coagulation times are usually abnormal if severe liver dysfunction
causes bleeding,Generalized bleeding and haemorrhage from
hepatic peliosis (cats) and vascular tumours,such as metastatic
haemangi-osarcoma,may result in regenerative anaemia,
Hepatoencephalopathy
This syndrome is caused by accumulation of toxins because of severe
hepatic dysfunction and/or porto-systemic shunting of blood,
Hyperammonaemia is a sensitive and specific marker for the
syndrome,although other metabolic disturbances are involved,
DIAGNOSTIC APPROACH TO LIVER DISEASE
In most cases,a tentative diagnosis can be deduced from the results of
laboratory tests in conjunction with imaging techniques,
However,the definitive diagnosis of primary liver disease usually
depends ultimately on histological examination of liver biopsy
specimens,
Primary extrahepatic causes of secondary liver disease will hopefully
be identified before biopsy is undertaken,
Thus a diagnostic approach to liver disease includes:
? Clinical history
? Physical examination
? Laboratory tests
? Examination of ascitic fluid
? Imaging:
Radiography
Ultrasonography
Angiography
Scintigraphy
? Liver biopsy.
The aims of laboratory testing are:
? To identify and characterize any hepatic dysfunction
? To identify possible primary causes of secondary liver disease
? To differentiate causes of icterus
? To evaluate potential anaesthetic risks
? To identify causes of anaemia of unknown origin
? To assess prognosis
? To assess the response to xenobiotics
? To monitor response to therapy,
There is a wide range of laboratory tests available for assessing liver
status,but they can be conveniently divided into four classes:
? General screening tests
? Markers of liver damage
? Liver function tests
? Prognostic indices.
The tests routinely available to the practising veterinary surgeon
and indications for their use will be discussed in detail,and more
specialized tests mentioned only briefly,
Urinary System
THE ROLE OF CLINICAL PATHOLOGY
Clinical pathology tests in the evaluation of a patient for the presence of
renal and/or urinary tract disease should be performed under the following
circumstances:
? When primary or secondary urinary system disease is suspected from the
presenting signs,clinical history or physical examination
? When a patient has a disease in another organ system that is known to be
potentially associated with concurrent or secondary renal or urinary tract
disease
? When screening 'at risk' patients as part of a general health check (e.g,as
part of a geriatric screening programme,before general anaesthesia,or
before administration of drugs that are known to be potentially
nephrotoxic,such as non-steroidal anti-inflammatory drugs,
aminoglycosides or oxytetracycline),
The accurate diagnosis of renal and urinary tract diseases requires
investigation by any or all of the following:
? Full history
? Full physical examination
? Imaging,Radiography - plain and contrast studies; sometimes dynamic
studies,Ultrasonography
? Urinalysis
? Blood chemistry
? Haematology
? Microbiological culture and sensitivity testing
? Tissue biopsy
? Surgical examination at laparoscopy or laparotomy
? Post-mortem examination
Urine should be analysed when:
? There is a change in its physical appearance,e.g,discoloration
? An animal passes frank blood in its urine
? An animal exhibits polydipsia
? An animal exhibits polyuria
? An animal exhibits urinary tenesmus
? An animal licks its external genitalia excessively
? An animal exhibits increased urinary frequency
? An animal is dehydrated
? An animal is vomiting
? An animal has signs of fluid accumulation in the abdomen (i.e,ascites) or
peripherally (subcutaneous oedema)
? Primary or secondary renal or urinary tract disease is suspected
? A urolith has been passed
? An animal exhibits pyrexia of unknown origin
? It is part of a routine screening test - juvenile,geriatric or before anaesthesia,
Urinalysis includes one or more of the following,
? Physical examination,color,smell,turbidity,content,
volume,specific gravity
? Chemical examination,pH,proteinuria,acetone,
glucose,urea
? Examination of sediment
? Bacterial culture
? Viral examination,
Clinical pathology panel for urinary
system disease
Plasma urea
Blood urea nitrogen
Plasma creatinine
Urea:creatinine ratio
Total plasma protein
Plasma albumin
Blasma sodium
Palsma potassium
Plasma chloride
Plasma calcium
Plasma phosphate
Glomerular function tests in dogs and cats
Endogenous creatinine clearance
Exogenous creatinine clearance
Inulin （菊酚） clearance
Iothalanate(碘酞酸盐） clearance
Filtration fraction
24 hour urine protein excretion
Urine phosphate:urine creatinine
RENAL AND URINARY TRACT DISEASES
Acute renal failure （ ARF） occurs when there is sudden onset
(within hours) of oliguria or azotaemia or both together,There
are many causes,categorized as follows:
? Pre-renal azotaemia,the kidneys produce a small volume of
concentrated urine,which is a physiological response to a
pre-renal problem
? Renal azotaemia,due to primary renal disease
? Post-renal azotaemia,due to diseases of the urinary excretory
tract,