Kidney function test


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Kidney function test

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  2. 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. 2
  3. 3. Classification – Kidney Function Test Based on Kidney Function & Clinical UtilityGroup I Overall functioning of Complete urine analysis kidneys Measurement of non-protein nitrogenous substances in blood Measurement of serum electrolytesGroup II Markers of glomerular Clearance tests filtration rateGroup III Markers of glomerular Microalbuminuria permeability ProteinuriaGroup IV Markers of tubular Osmolality – plasma & urine dysfunction Concentration and dilution tests Tests to assess renal acidification 3
  4. 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 4
  5. 5. Clearance tests Types of Clearance tests Endogenous ExogenousCreatinine InulinUrea Para-amino hippuric acid (PAHA)Uric acid Diodrast (di-iodo pyridone acetic acid) Calculation: U X V PWhere: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) 5
  6. 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 6
  7. 7. Urine Analysis – Physical Characteristics VolumeNormal Range Conditions increased Conditions decreased1000 – 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 7
  8. 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 8
  9. 9. Urine Analysis – Physical Characteristics Specific gravity Instrument: ‘Urinometer’ Fixed specific gravity of 1.010: Chronic renal failureNormal Range Conditions increased Conditions decreased1.016 to 1.022 Diabetes mellitus Excess water intake Nephrosis Chronic nephritis Excessive sweating Diabetes insipidus 9
  10. 10. Urine analysis – Chemical CharacteristicsAbnormal Name of the Associated Clinical CharacteristicsConstituent Test ConditionsReducing Benedict’s Diabetes mellitusSugar or test Gestational Diabetessubstance Renal glycosuria Essential Pentosuria Galactosemia Hereditary fructose intolerance Essential fructosuria Lactosuria HomogentisicaciduriaKetone Rothera’s Diabetic ketoacidosisbodies test Starvation ketoacidosis Gerhad’s test Von Gierke’s disease 10
  11. 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. 11
  12. 12. Urine analysis – Chemical CharacteristicsAbnormal Name of the Associated Clinical CharacteristicsConstituent Test ConditionsProteins Heat & Acetic Glomerulonephritis acid test Pyelonephritis Sulphosalicylic Nephrotic acid test syndrome Heller’s testBlood Benzidine test Stones in ureter Glomerulonephritis Renal tuberculosis Trauma to genito- urinary tract Carcinoma urinary bladder Urinary tract infection 12
  13. 13. Urine analysis – Chemical CharacteristicsAbnormal Name of the Associated Clinical CharacteristicsConstituent Test ConditionsBile salts Hay’s test Viral hepatitis Alcoholic hepatitis Toxic hepatitis Drug induced hepatitis Obstructive jaundiceBile pigments Fouchet’s test 13
  14. 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 14
  15. 15. Serum ElectrolytesSegment of Nephron Substance Substance secreted reabsorbedProximal Convoluted Tubule (PCT) Sodium H+ Chloride Organic acids and Bicarbonate bases Water (Obligatory) NH4+Loop of Henle Sodium --- Chloride Calcium MagnesiumDistal Convoluted Tubule (DCT) Sodium H+ Chloride K+ Water (Facultative) NH4+ Reabsorption and secretion of electrolytes is essentialfor the maintenance of body’s acid-base balance 15
  16. 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 16
  17. 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 17
  18. 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 18
  19. 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 19
  20. 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 20
  21. 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 21
  22. 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 22
  23. 23. Kidney Function Test - SummaryMeasurement of GFR Clearance testsEndogenous substance used for clearance CreatininetestsExogenous substance used for clearance InulintestesVolume, Appearance, Colour, Odour, Specific Physical CharacteristicsgravityMeasurement of specific gravity UrinometerReducing substance, Ketone bodies, Proteins, Abnormal chemicalBlood, Bile salts and Bile pigments constituentsEarly detection of Diabetic and hypertensive MicroalbuminnephropathySpecific gravity, Concentration test, Urine Renal tubular functionvolume, Osmolality, Dilution test,Acidification 23
  24. 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 24