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2.  A 60 year old male was admitted to the casualty
with the complaints of vomiting, pain in the lower
back and blurring of vision. General physical
examination showed patient was semi-conscious
and disoriented. On further evaluation, patient
had decreased urine output.
 What is your probable diagnosis?
 Suggest the biochemical investigations to confirm
your diagnosis.
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3. Classification – Kidney Function Test
 Based on Kidney Function & Clinical Utility
Group I Overall functioning of Complete urine analysis
kidneys Measurement of non-protein
nitrogenous substances in blood
Measurement of serum electrolytes
Group II Markers of glomerular Clearance tests
filtration rate
Group III Markers of glomerular Microalbuminuria
permeability Proteinuria
Group IV Markers of tubular Osmolality – plasma & urine
dysfunction Concentration and dilution tests
Tests to assess renal acidification
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4. Clearance tests
 Test for glomerular filtration rate (GFR)
 Useful index for the assessment of severity of
kidney damage
 Definition: ‘Clearance is defined as the quantity
of blood or plasma that is completely cleared of
a substance per unit time’
 Alternatively → ml of plasma which contains
the amount of that substance excreted by
kidney within a minute
 Units: ml/min
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5. Clearance tests
Types of Clearance tests
Endogenous Exogenous
Creatinine Inulin
Urea Para-amino hippuric acid (PAHA)
Uric acid Diodrast (di-iodo pyridone acetic acid)
 Calculation: U X V
P
Where:
U = concentration of substance in urine (mg/dl)
V = volume of urine excreted per minute (ml/min)
P = concentration of substance in plasma/serum (mg/dl)
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6. Clearance tests
 Creatinine clearance:
- Otto Folin: estimated it in 1904
- formation of creatinine is continuous, spontaneous
and non-enzymatic
- dependent on muscle mass of the body
- Reference range: 85 to 125 ml/min
 Inulin clearance:
- polysaccharide of fructose
- neither absorbed nor secreted by tubules
- Reference value: 125ml/min
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7. Urine Analysis – Physical Characteristics
 Volume
Normal Range Conditions increased Conditions decreased
1000 – 1800 ml/day Diuretic therapy Excess sweating
Diabetes insipidus Dehydration
Diabetes mellitus Acute renal failure
 Polyuria: ↑Urine output → > 2.5 litres/day
 Oliguria: ↓ Urine outout → 300 to 500 ml/day
 Anuria: ↓↓↓ Urine output → < 50 ml/day
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8. Urine Analysis – Physical Characteristics
 Appearance: Clear and transparent
 Turbid → Excess phosphates, Urinary tract infection
 Odour: Aromatic
 Smell of acetone: Diabetic ketoacidosis
 Fishy: Presence of blood
 Colour: Amber-yellow
 High colour → Jaundice
 Red colour → Blood
 pH: 6.0 (Range: 5.5 to 7.5)
 ↓ → Metabolic acidosis, ↑ → Metabolic alkalosis
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9. Urine Analysis – Physical Characteristics
 Specific gravity
 Instrument: ‘Urinometer’
 Fixed specific gravity of 1.010:
Chronic renal failure
Normal Range Conditions increased Conditions decreased
1.016 to 1.022 Diabetes mellitus Excess water intake
Nephrosis Chronic nephritis
Excessive sweating Diabetes insipidus
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10. Urine analysis – Chemical Characteristics
Abnormal Name of the Associated Clinical Characteristics
Constituent Test Conditions
Reducing Benedict’s Diabetes mellitus
Sugar or test Gestational Diabetes
substance Renal glycosuria
Essential Pentosuria
Galactosemia
Hereditary fructose
intolerance
Essential fructosuria
Lactosuria
Homogentisicaciduria
Ketone Rothera’s Diabetic ketoacidosis
bodies test Starvation ketoacidosis
Gerhad’s test Von Gierke’s disease
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11.  A 10 year old boy was admitted to the paediatrics
ward with facial puffiness and swelling over the
dorsum of the foot. Past history revealed that he
was treated for fever about 6 weeks back. Physical
examination findings shoed pitting type pedal
oedema. Abdominal examination findings
showed distension with free fluid in the
abdomen.
 What is your probable diagnosis?
 Suggest the biochemical investigations to confirm
your diagnosis.
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12. Urine analysis – Chemical Characteristics
Abnormal Name of the Associated Clinical Characteristics
Constituent Test Conditions
Proteins Heat & Acetic Glomerulonephritis
acid test Pyelonephritis
Sulphosalicylic Nephrotic
acid test syndrome
Heller’s test
Blood Benzidine test Stones in ureter
Glomerulonephritis
Renal tuberculosis
Trauma to genito-
urinary tract
Carcinoma urinary
bladder
Urinary tract
infection 12

13. Urine analysis – Chemical Characteristics
Abnormal Name of the Associated Clinical Characteristics
Constituent Test Conditions
Bile salts Hay’s test Viral hepatitis
Alcoholic hepatitis
Toxic hepatitis
Drug induced hepatitis
Obstructive jaundice
Bile pigments Fouchet’s
test
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14. NPN Substances measurement
 Major route of excretion → Urine
 ↑ levels is seen in kidney dysfunction
 Blood Urea
 End product of protein metabolism
 Methods: DAM, Berthalot, Urease-GLDH
 Serum Uric acid
 End product of purine metabolism
 Methods: Caraway, Uricase
 Serum Creatinine
 Anhydride form of creatine formed in muscles
 Method: Jaffe’s kinetic
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15. Serum Electrolytes
Segment of Nephron Substance Substance secreted
reabsorbed
Proximal Convoluted Tubule (PCT) Sodium H+
Chloride Organic acids and
Bicarbonate bases
Water (Obligatory) NH4+
Loop of Henle Sodium ---
Chloride
Calcium
Magnesium
Distal Convoluted Tubule (DCT) Sodium H+
Chloride K+
Water (Facultative) NH4+
 Reabsorption and secretion of electrolytes is essential
for the maintenance of body’s acid-base balance
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16. Markers of Glomerular Permeability
 Microalbuminuria
 Syn: Minimal albuminuria/pauci-albuminuria
 Small quantity of albumin in urine
 30 to 300 mg/day
 Cause: abnormally high permeability for albumin in
the renal glomerulus
 Use: early marker for nephropathy in patients
with diabetes and hypertensiom
 Measurement: Immunoturbidimetric method,
ELISA
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17. Tests for renal tubular function
 Measurement of Urine Volume
 Urine is collected separately during day and during
night (6 AM to 6 PM & 6 PM to 6 AM)
 Normally night volume is only 50% of day volume
 ↑ excretion of urine in night (nocturia) → tubular
dysfunction
 Measurement of Osmolality
 Instrument: ‘Osmometer’
 Urine Osmolality: 60 to 1200 milliosmol/kg
 Plasma Osmolality: 285 to 300 milliosmol/kg
 Osmolality of urine/plasma: 3 to 4.5
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18. Tests for renal tubular function
 Specific gravity
 Instrument: ‘Urinometer’
 earliest manifestation of renal disease → difficulty in
concentrating the urine → alterations in specific
gravity
 Concentration test
 Subject is not allowed to consume food or water after
6 PM till next day 7 AM, when the bladder is emptied
 A second specimen is collected one hour later and
specific gravity is measured
 > 1.022 indicates adequate renal function
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19. Tests for renal tubular function
 Dilution tests
 Subject is not allowed to drink water after
midnight
 Morning after emptying bladder, water load of
1200ml is given for about 30 min
 Hourly urine samples is collected seperately for
next 4 hours
 Each sample: Volume, specific gravity and
osmolality is measured
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20. Tests for renal tubular function
 Dilution tests…
 Normal response: Almost all water load is
excreted by 4 hours
- One of the 4 samples shows specific gravity
falling to 1.003 and osmolality to 50
milliosmol/kg
 Advantage:
- More sensitive test
- Feasible
- Less harmful than concentration test
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21. Tests for renal tubular function
 Urinary acidification
 Syn: Acid load test
 0.1 g/Kg body weight of ammonium chloride is
given as enteric coated preparation
 Fate of ammonium chloride:
 NH4Cl → NH4+ + Cl-
 NH4+ → converted to urea by liver
 Cl- + H+ → HCl → excreted in urine to produce
acidification
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22. Tests for renal tubular function
 Urinary acidification…
 Urine is collected hourly – from 2 to 8 hours after
the ingestion
 pH and acid excretion of each sample is noted
 Normal response: At least one sample →
- pH: 5.3
- ammonia excretion: 30 to 90 mmol/hour
 Chronic renal failure: pH is low
 Renal tubular acidosis: pH of 5.3 is not achieved
 Contraindication: Liver disease
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23. Kidney Function Test - Summary
Measurement of GFR Clearance tests
Endogenous substance used for clearance Creatinine
tests
Exogenous substance used for clearance Inulin
testes
Volume, Appearance, Colour, Odour, Specific Physical Characteristics
gravity
Measurement of specific gravity Urinometer
Reducing substance, Ketone bodies, Proteins, Abnormal chemical
Blood, Bile salts and Bile pigments constituents
Early detection of Diabetic and hypertensive Microalbumin
nephropathy
Specific gravity, Concentration test, Urine Renal tubular function
volume, Osmolality, Dilution test,
Acidification 23

24. Examination Tips
• Classify kidney function tests. Describe any three
tests with its clinical importance.
• Clearance tests
• Tests used for assessment of renal tubular
functions
• Microalbuminuria
• Specific gravity of urine
• Test for ketone bodies in urine
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