3. Renal function tests
1. Tests to asses glomerular function
2. Tests to asses tubular function
3. Routine urine analysis
4. Analysis of blood/serum
4. Tests to asses glomerular function
• The blood supply to kidneys is relatively
large. About 1200 ml of blood (650 ml plasma)
passes through the kidneys, every minute.
• From this, about 120-125 ml is filtered per
minute by the kidneys and this is referred to
as glomerular filtration rate (GFR).
• Normal GFR is (120-125 ml/min).
• The glomerular filtrate formed in an adult is
about 175-180 litres per day, out of which
only 1.5 litres is excreted as urine.
5. • The process of urine formation basically
involves two steps— glomerular filtration
and tubular reabsorption.
6. • Measurement of the clearance is
predominantly a test of glomerular filtration
rate (GFR).
• Clearance, is defined as the volume of
plasma that would be completely cleared of
a substance per minute.
8. Tests to asses glomerular function
1. Creatinine clearance:
C=UV/P
where U is the urine creatinine concentration, P is
the plasma creatinine concentration and V is the
urine flow in ml/min (The 24 hr urine collection is
not necessary for the creatinine clearance test).
9. Creatinine clearance test:
Reference values: 100-125(M) & 90-115(F)
Significance: decreased values below 75% -impairment of
renal function and renal damage.
• Dehydration
• Glomerulonephritis
• Shock
• Acute nephrotic syndrome
• Acute and chronic renal failure
Creatinine level in blood: 0 .8 to 1.4 mg/dL
10. Urea clearance
• Urea clearance is defined as the volume (ml)of
plasma that would be completely cleared
of urea per minute.
• It is calculated by the formula
11. • If the output of urine is more than 2 ml
per minute. This is referred to as maximum
urea clearance and the normal value is
around 75 ml/min.
• Standard urea clearance : when the volume
of urine is less than 2 ml/min. This is
known as standard urea clearance. normal
value is around 54 ml/min.
12. Urea clearance :
• Partially reabsorbed by the renal tubules.
• Clearance is less than GFR.
• Significance : value below 75% of normal is
abnormal.
• The values fall progressively with failing renal
function.
14. TESTS FOR TUBULAR FUNCTION
SPECIFIC GRAVITY :
The simplest test of tubular function is the measure-
ment of the specific gravity (SG) of urine.
Normal = 1.015-1.025
Decreased : excess water intake,DI,nephritis.
Increased :excess perspiration,DM,nephrosis.
15. CONCENTRATION TEST:
SG measured after 12 hr fast.
SG more than 1.022 –adequate renal function.
• In moderate forms of kidney damage, the
inability to excrete the waste products may be
counterbalanced by large urine output.
Thus, the earliest manifestation of renal
disease may be the difficulty in concentrating
the urine.
16. DILUTION TEST:
• BLADDER EMPTIED AT 7AM
• WATER LOAD 1200 ml in 30 min.
• Urine samples collected for next 4 hours.
• A normal person will excrete almost all the
water load within 4 hours and the specific
gravity of at least one sample should fall to
1.003.
• The test is more sensitive and less harmful
than concentration test.
18. LIVER FUNCTION TESTS
• TESTS BASED ON EXCRETORY FUNCTION
• TESTS BASED ON SYNTHETIC FUNCTION
• DETOXIFICATION
• DIAGNOSTIC ENZYMES
19. BASED ON EXCRETORY FUNCTION:
Estimation of Bilirubin
• Bilirubin is the end product of haem catabolism
• It is transported to liver by albumin
• In liver bilirubin is conjugated with glucuronate &
secreted into intestine with bile
Total Serum level =0.2-1.0 mg/dl
Unconjugated= 0.2-0.7 mg/dl
Conjugated = 0.1-0.4 mg/dl
20. • Van den bergh reaction- detection of serum
bilirubin and the type of jaundice.
Principle: It is based on the formation of a
purple-colored azobilirubin, when serum
containing bilirubin is allowed to react with
freshly prepared diazo reagent.
21. • Van den Bergh Diazo reagent: It is prepared
by mixing sulfanilic acid & sodium nitrite in
HCl .
• When bilirubin is conjugated,the purple color
is produced immediately on mixing with
the reagent, the response is said to be van
den Bergh direct positive.
22. • When the bilirubin is unconjugated,the color
is obtained only when alcohol is added,
and this response is known as indirect
positive.
• If both conjugated and unconjugated
bilirubinsare present in increased amounts,
a purple color is produced immediately and
the color is intensified on adding alcohol. Then
the reaction is called biphasic.
23. Pattern of van den Bergh reaction in
different types of jaundice
Types of jaundice Causes Types of bilirubin in
blood
Prehepatic Rh incompatibility,Sickle
cell anemia
Unconjugated ↑
(indirect positive)
Hepatic Viral hepatitis—A, B, C
Toxic hepatitis—alcohol
Conjugated ↑
Unconjugated ↑
(biphasic reaction)
Posthepatic Gallstones,
Pancreatic tumor
Conjugated ↑
(direct positive)
24. • Urinary bilirubin:conjugated bilirubin is
detected by fouchets test.
• Urinary urobilinogen: extreted in hemolytic
jaundice. Urobilinogen in urine reacts with
Ehrlich's reagent to form a red color
• Urine bile salts :Hays test
25. Synthetic function
• The liver synthesizes albumin
• It represents a major synthetic protein and is
marker for ability of liver synthesis.
Albumin : half life 20 days
blood : 3.5-5 g/dl.
Prothrombin time :half life is 6hrs.
PT is prolonged in hepatic disorders.
29. GASTRIC FUNCTION TESTS
Pentagastrin stimulation test
• Pentagastrin is a synthetic peptide which
stimulates the gastric secretion in a
manner similar to the natural gastrin.
• The stomach contents are aspirated by Ryle’s
tube in a fasting condition.This is referred to
as residual juice.
30.
31. • The gastric juice elaborated for the next one
hour is collected and pooled which represents
the basal secretion.
• Pentagastrin (5 mg/kg body weight) is now
given to stimulate gastric secretion. The
gastric juice is collected at 15 minute intervals
for one hour. This represents the maximum
secretion.
32. • Basal acid output (BAO) refers to the acid
output (millimol/hour) under the basal
conditions i.e. basal secretion. = 2-4 mmol/hr
• Maximal acid output (MAO) represents the
acid output (millimol per hour) after the
gastric stimulation by pentagastrin i.e.
maximum secretion. = 15-50 mmol/hr.
33. Augmented histamine test meal
• Histamine is a powerful stimulant of gastric
secretion. The basal gastric secretion is
collected for one hour.
• Histamine (0.04 mg/kg body weight) is
administered subcutaneously and the gastric
contents are aspirated for the next one
hour (at 15 minute intervals).
• The acid content is measured in all these
samples.
34. Abnormalities of gastric function
• Increased gastric HCI secretion is found in
Zollinger-Ellison syndrome (a tumor of gastrin
secreting cells of the pancreas), chronic
duodenal ulcer, gastric cell hyperplasia,
excessive histamine production etc.
• A decrease in gastric HCI is observed in
gastritis, gastric carcinoma, pernicious anemia
etc.
35. PANCREATIC FUNCTION TESTS
• Pancreatic enzymes in serum : Serum
amylase and lipase measurements are
commonly employed to assess the pancreatic
function. Both these enzyme activities are
elevated in acute pancreatitis, obstruction
in the intestine and/or pancreatic duct.
