Laboratory tests of renal
function
Junfu Huang
Southwestern Hospital
TMMU
Anatomy of Kidney
Functions of the kidney
? Excretion of Metabolite Waste,
urea,uric acid,creatinine
? Urine Production,regulation of
homeostasis,water,acid base
balance
? Endocrine Function,renin,
erythropoietin,1,25 -
dihydroxycholecalciferol
Renal function tests
? Detect renal damage
? Monitor functional damage
? Distinguish between
impairment and failure
Kidney Function
? A plumbers view
F i lt e r
P r o c e s s o r
I n p u t
A r t e ri a l
O u t p u t
V e n o u s
O u t p u t
U ri n e
How do you know it’s broken?
? NO Urine!
? Clinical
symptoms
? Tests
F i lt e r
P r o c e s s o r
I n p u t
A r t e ri a l
O u t p u t
V e n o u s
O u t p u t
U ri n e
Where can it break?
? Pre-renal
? Renal
? Post-renal
F i lt e r
P r o c e s s o r
I n p u t
A r t e ri a l
O u t p u t
V e n o u s
O u t p u t
U ri n e
Laboratory tests of renal
function
? Glomerular Function Tests
? Renal Tubular Function Tests
Section 1 Investigation of
Glomerular Function
? Renal Blood Flow,1200-1400ml/min
? Renal Plasma, 600-800ml/min
? 20% of plasma,glomerular filtration
GFR:Glomerular Filtrtion Rate
Concept
Renal Clerance
? Concept
Virtual volume of plasma from which
the substance in question has been
completely removed during a given time
interval.
C=UV/P
U:urine concentrtion P:plasma con.
V:urine flow rate
Usefulness of Renal Clerance
? Freely filtrated,neither secreted,nor
reabsorbed,Inulin,GFR Determination
? Freely Filtrated,small amounts secreted,
without reabsorption,Cretinine:GFR
? Free filtrated,completely reabsorption,
Glucose
Tubular Maxima Reabsorption Rate
Inulin Clerance
? Polymer of fructose
? MW:5500
? Free filtration,without secretion and
reabsorption
? GFR
? Method
? Reference Interval,2.0-2.3ml/min
Endogenous Creatinine
Clearance
? 100g,98% stored in musle,MW:113
? Cretine phosphate---cretine— cretinine
? Freely filtration,small mounts,secretion
? Exogenous and Endogenous Creatinine
? Grossly Investigate the GFR
? Method
24h urine collection method
modified 4h urine collection method
Clerance Correction：
Ccr x SBSA/IBSA
Plasma urea
? Secreted and reabsorbed by tubules,
freely filtrated
? quick,simple measurement
? wide reference range 3 - 8 mmol/L
? sensitive but non-specific index of
illness
Factors influ encing plasma
urea concentra tion
GIT
pro tei n
Kid ne y
fil trati on
?
Li ver
amin o
ac id s
?
Plas ma
ure a
?
rea bs orp tio n
excre tio n
Ti ss ue
pro tei n
?
?
Dis tri bu tio n
volu me
Urea excretion
? filtered at glomerulus
? about 40% filtered urea is reabsorbed
by renal tubules in health
? more urea is reabsorbed if rate of
tubular flow is slow
? tubular flow rate is slow when there is
renal hypoperfusion
Increased plasma urea
? GI bleed
? trauma
? renal hypoperfusion
decreased RBF
decreased ECFV
? acute renal
impairment
? chronic renal
disease
? post-renal
obstruction
calculus
tumour
Urea
? Useful test but must be
interpreted with great care
? Always consider input,output
and patient’s fluid volume
Plasma creatinine
? 50 - 140 umol/L
? increases in concentration as GFR
decreases
? analytical interferences
? (acetoacetate - DKA)
? NOT proportional to renal damage
Plasma Creatinine
GFR
[pCreat]
140 mL/min0 mL/min
Change within an
individual patient is
usually more important
than the absolute value
Plasma creatinine in chronic
renal disease
? May increase to 1000 umol/L
? Plot of recipricol of plasma creatinine
concentration predicts when
intervention is required in end stage
renal failure
Time
1/ [pCreat]
Plasma Uric Acid
? 20%:foods;80%:purine metabolism
? Small amounts,conjugated with
albumin
? Free Filtrated,98%-100%:reabsorbed
? Plasma UA concentration,depend on
glomerular filtration and tubular
reabsorption
Progression of chronic renal
disease
1
C reat inine c learanc e
m L/ m in
Plas m a c hange
60 - 120 none
30 - 60 inc reas ed c reat inine,
inc reas ed urea
20 - 30 inc reas ed pot as s ium,
dec reas ed bic arbonate
10 -20 inc reas ed phos phate,
inc reas ed uric ac id
Plasma Cystatin C
? Cysteine proteinase inhibitor
? Produced by nucleated cells
? MW:13000,free filtration,reabsorbed
and metabolized by tubules
? Plasma CysC concentrtion,depend on
glomerular filtration
Carbamylated hemoglobin
? Urea— blood— cyanate— Hb
carbamylated— CarHb
? ARF,no changes(1 weeks)
? CRF,increase
Laboratory tests of renal
function
? glomerular filtration rate impractical
? creatinine clearance unreliable
? plasma creatinine specific but insensitive
? plasma urea subject to problems
? urine volume often forgotten!
Section 2 Investigation of Tubular
Function
? Distal nephron Function tests
1,Mosenthal test
Concentration dilution test
8 AM,Voiding and Discarded
10,12,14,16,18,20:00 and 8:00 next day:
collecting urine samples
Determing the urine volume and gravity
? 2.Urine Osmolarity
? 3.Acute Oliguria
Prenal?
Renal?
? Proximal tubular Function tests
1.Low MW proteins in urine
2.Tubular maximal glucose reabsorption
3.Tubular maximal PAH secretion
4.Amino acide in urine
Fanconi Syndrome
Section 3 Effective Renal Blood
Flow
? Isotope Method:131I-OIH
? PAH Clearance:
20%:filtrated,80%:secreted by tubules
Section 4 Investigation of renal
tubular acidosis
? Tubular Acidosis:I,II,III.IV
? I:distal form
? II:proximal form
NH4Cl Loading Test
? Oral administration of NH4Cl
? Artificial Metabolic Acidosis
? Urine Sample Collection
? pH determination
Fraction of HCO3- excretion
? HCO3-:85-90%,reabsorbed by proximal
tubules; 10-15%,reabsorbed by distal tubules
? Oral Administration of NaHCO3
? Urine Collection
? Determination of PCr,UCr,PHCO3,UHCO3
? Caculation:
FEHCO3=UHCO3.PCr/UCr.PHCO3
function
Junfu Huang
Southwestern Hospital
TMMU
Anatomy of Kidney
Functions of the kidney
? Excretion of Metabolite Waste,
urea,uric acid,creatinine
? Urine Production,regulation of
homeostasis,water,acid base
balance
? Endocrine Function,renin,
erythropoietin,1,25 -
dihydroxycholecalciferol
Renal function tests
? Detect renal damage
? Monitor functional damage
? Distinguish between
impairment and failure
Kidney Function
? A plumbers view
F i lt e r
P r o c e s s o r
I n p u t
A r t e ri a l
O u t p u t
V e n o u s
O u t p u t
U ri n e
How do you know it’s broken?
? NO Urine!
? Clinical
symptoms
? Tests
F i lt e r
P r o c e s s o r
I n p u t
A r t e ri a l
O u t p u t
V e n o u s
O u t p u t
U ri n e
Where can it break?
? Pre-renal
? Renal
? Post-renal
F i lt e r
P r o c e s s o r
I n p u t
A r t e ri a l
O u t p u t
V e n o u s
O u t p u t
U ri n e
Laboratory tests of renal
function
? Glomerular Function Tests
? Renal Tubular Function Tests
Section 1 Investigation of
Glomerular Function
? Renal Blood Flow,1200-1400ml/min
? Renal Plasma, 600-800ml/min
? 20% of plasma,glomerular filtration
GFR:Glomerular Filtrtion Rate
Concept
Renal Clerance
? Concept
Virtual volume of plasma from which
the substance in question has been
completely removed during a given time
interval.
C=UV/P
U:urine concentrtion P:plasma con.
V:urine flow rate
Usefulness of Renal Clerance
? Freely filtrated,neither secreted,nor
reabsorbed,Inulin,GFR Determination
? Freely Filtrated,small amounts secreted,
without reabsorption,Cretinine:GFR
? Free filtrated,completely reabsorption,
Glucose
Tubular Maxima Reabsorption Rate
Inulin Clerance
? Polymer of fructose
? MW:5500
? Free filtration,without secretion and
reabsorption
? GFR
? Method
? Reference Interval,2.0-2.3ml/min
Endogenous Creatinine
Clearance
? 100g,98% stored in musle,MW:113
? Cretine phosphate---cretine— cretinine
? Freely filtration,small mounts,secretion
? Exogenous and Endogenous Creatinine
? Grossly Investigate the GFR
? Method
24h urine collection method
modified 4h urine collection method
Clerance Correction：
Ccr x SBSA/IBSA
Plasma urea
? Secreted and reabsorbed by tubules,
freely filtrated
? quick,simple measurement
? wide reference range 3 - 8 mmol/L
? sensitive but non-specific index of
illness
Factors influ encing plasma
urea concentra tion
GIT
pro tei n
Kid ne y
fil trati on
?
Li ver
amin o
ac id s
?
Plas ma
ure a
?
rea bs orp tio n
excre tio n
Ti ss ue
pro tei n
?
?
Dis tri bu tio n
volu me
Urea excretion
? filtered at glomerulus
? about 40% filtered urea is reabsorbed
by renal tubules in health
? more urea is reabsorbed if rate of
tubular flow is slow
? tubular flow rate is slow when there is
renal hypoperfusion
Increased plasma urea
? GI bleed
? trauma
? renal hypoperfusion
decreased RBF
decreased ECFV
? acute renal
impairment
? chronic renal
disease
? post-renal
obstruction
calculus
tumour
Urea
? Useful test but must be
interpreted with great care
? Always consider input,output
and patient’s fluid volume
Plasma creatinine
? 50 - 140 umol/L
? increases in concentration as GFR
decreases
? analytical interferences
? (acetoacetate - DKA)
? NOT proportional to renal damage
Plasma Creatinine
GFR
[pCreat]
140 mL/min0 mL/min
Change within an
individual patient is
usually more important
than the absolute value
Plasma creatinine in chronic
renal disease
? May increase to 1000 umol/L
? Plot of recipricol of plasma creatinine
concentration predicts when
intervention is required in end stage
renal failure
Time
1/ [pCreat]
Plasma Uric Acid
? 20%:foods;80%:purine metabolism
? Small amounts,conjugated with
albumin
? Free Filtrated,98%-100%:reabsorbed
? Plasma UA concentration,depend on
glomerular filtration and tubular
reabsorption
Progression of chronic renal
disease
1
C reat inine c learanc e
m L/ m in
Plas m a c hange
60 - 120 none
30 - 60 inc reas ed c reat inine,
inc reas ed urea
20 - 30 inc reas ed pot as s ium,
dec reas ed bic arbonate
10 -20 inc reas ed phos phate,
inc reas ed uric ac id
Plasma Cystatin C
? Cysteine proteinase inhibitor
? Produced by nucleated cells
? MW:13000,free filtration,reabsorbed
and metabolized by tubules
? Plasma CysC concentrtion,depend on
glomerular filtration
Carbamylated hemoglobin
? Urea— blood— cyanate— Hb
carbamylated— CarHb
? ARF,no changes(1 weeks)
? CRF,increase
Laboratory tests of renal
function
? glomerular filtration rate impractical
? creatinine clearance unreliable
? plasma creatinine specific but insensitive
? plasma urea subject to problems
? urine volume often forgotten!
Section 2 Investigation of Tubular
Function
? Distal nephron Function tests
1,Mosenthal test
Concentration dilution test
8 AM,Voiding and Discarded
10,12,14,16,18,20:00 and 8:00 next day:
collecting urine samples
Determing the urine volume and gravity
? 2.Urine Osmolarity
? 3.Acute Oliguria
Prenal?
Renal?
? Proximal tubular Function tests
1.Low MW proteins in urine
2.Tubular maximal glucose reabsorption
3.Tubular maximal PAH secretion
4.Amino acide in urine
Fanconi Syndrome
Section 3 Effective Renal Blood
Flow
? Isotope Method:131I-OIH
? PAH Clearance:
20%:filtrated,80%:secreted by tubules
Section 4 Investigation of renal
tubular acidosis
? Tubular Acidosis:I,II,III.IV
? I:distal form
? II:proximal form
NH4Cl Loading Test
? Oral administration of NH4Cl
? Artificial Metabolic Acidosis
? Urine Sample Collection
? pH determination
Fraction of HCO3- excretion
? HCO3-:85-90%,reabsorbed by proximal
tubules; 10-15%,reabsorbed by distal tubules
? Oral Administration of NaHCO3
? Urine Collection
? Determination of PCr,UCr,PHCO3,UHCO3
? Caculation:
FEHCO3=UHCO3.PCr/UCr.PHCO3
