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RENAL FUNCTION TESTS

RENAL FUNCTION TESTS. Vital role in body’s homeostasis. Functional unit of kidney is nephron. Glomerular capillary network Bowman’s capsule Proximal tubule Loop of henle Distal tubule Collecting duct. STEPS IN URINE FORMATION. GLOMERULAR FILTRATION

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RENAL FUNCTION TESTS

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  1. RENAL FUNCTION TESTS

  2. Vital role in body’s homeostasis

  3. Functional unit of kidney is nephron Glomerular capillary network Bowman’s capsule Proximal tubule Loop of henle Distal tubule Collecting duct

  4. STEPS IN URINE FORMATION • GLOMERULAR FILTRATION • TUBULAR REABSORPTION • TUBULAR SECRETION

  5. RATE OF URINARY EXCRETION OF ANY SOLUTE = RATE OF GLOMERULAR FILTRATION + RATE OF SECRETION - RATE OF REABSORPTION

  6. PHYSICAL TESTS • URINE VOLUME • Assessment of fluid balance and kidney function. Normal value; adult : 800-2500 mL/day children : 500-1400 mL/day

  7. CLINICAL IMPLICATIONS • 1. polyuria with elevated BUN and creatinine . diabetic ketoacidosis partial obstruction of urinary tract tubular necrosis • 2.polyuria with normal BUN and creatinine. diabetes mellitus and diabetes insipidus tumours of brain and spinal cord

  8. 3.oliguria Renal causes renal ischemia renal disease due to toxic agents Dehydration caused by prolonged vomiting,diarrhoea,burns Obstruction of some area of the urinary tract Cardiac insufficiency • 4.anuria Complete urinary tract obstruction Acute cortical necrosis Glomerulonephritis Acute tubular necrosis

  9. INTERFERING FACTORS • 1.polyuria a)intravenous glucose or saline b)thiazides c)coffee,alcohol,tea,caffeine • 2.oliguria a)dehydration b)excessive salt intake

  10. 2.URINE COLOUR • Yellow colour due to urochrome. • Normal; Pale yellow to amber Straw colour- low SG Amber colour-high SG

  11. CLINICAL IMPLICATIONS • Almost colourless urine; large fluid intake chronic interstitial nephritis untreated diabetes mellitus diabetes insipidus alcohol and caffeine ingestion diuretic therapy nervousness • Orangecolour; fever carrots or vitamin A phenazopyridine, nitrofurantoin

  12. Green urine; pseudomonal infection chlorophyll • Red urine RBCs haemoglobin myoglobin porphyrins • Black urine melanin phenol poisoning • Smoky urine - RBCs • Milky urine - fat,cystinuria,WBCs

  13. INTERFERING FACTORS • Drugs alter the colour green - indomethacin brown - chloroquine,furazolidone pink to brown - laxatives red-pink - daunorubicin orange - rifampicin blue urine - triamterene black urine - chloroquine metronidazole

  14. 3.URINE ODOUR • Faint odour owing to the presence of volatile oils. normal; aromatic odour.

  15. CLINICAL IMPLICATIONS • Diabetes mellitus patients urine have a fruity odour. • UTIs result in foul-smelling urine . • Infants with a inherited disorder of amino acid metabolism urine smells like burnt sugar. • Cystinuria result in sulfurous odour.

  16. 4.URINE SPECIFIC GRAVITY (SG) • Measurement of the kidneys ability to concentrate urine. • Compares the density of urine against the density of distilled water. • Normal; 1.005-1.030

  17. CLINICAL IMPLICATIONS • Hyposthenuria ( low SG,1.001-1.010) diabetes insipidus • Hypersthenuria(increased SG, 1.025-1.035) diabetes mellitus nephrosis excessive water loss congestive heart failure

  18. INTERFERING FACTORS • Elevated readings Moderate amounts of protein Patients receiving intravenous albumin. Diuretics and antibiotics

  19. 5. URINE pH • pH is an indicator of the renal tubules ability. normal; can vary widely 4.6 - 8 average value is about 6 (acidic).

  20. CLINICAL IMPLICATIONS • 1. Acidic urine (pH<7.0) Starvation UTIs caused by Escherichia coli respiratory acidosis pyrexia • 2. Alkaline urine (pH>7.0) UTIs caused by urea-splitting bacteria renal tubular acidosis respiratory alkalosis potassium depletion

  21. INTERFERING FACTORS • alkaline urine Sodium bicarbonate potassium citrate acetazolamide • acidic urine ammonium chloride mandelic acid

  22. CHEMICAL EXAMINATION OF URINE • ENDOGENOUS MARKERS a) SERUM CREATININE • breakdown product of muscle creatine phosphate. • excreted by glomerular filtration and tubular secretion. • doubles with each 50% decrease in GFR. if SCr is 1mg/dl, 100% renal function 2mg/dl, 50% renal function

  23. Normal; URINE CREATININE men : 14-26mg/kg/24 hours women: 11-20mg/kg/24 hours SERUM CREATININE men : 0.6-1.2 mg/dL women : o.4-1.0 mg/dL

  24. CLINICAL IMPLICATIONS • SERUM CREATININE increased in; ingestion of roast meat muscle disease prerenalazotemia postrenalazotemia decreased in; pregnancy

  25. SERUM CREATININE INCREASED BY DECREASED BY ACE inhibitors Ascorbic acid AlprazolamCaptopril Aspirin Dopamine CefiximeValproic acid Methotrexate Prednisone Ranitidine Triamterene Ibuprofen

  26. CLINICAL IMPLICATIONS URINE CREATININE Increased by decreased by Acromegaly Anemia Hypothyroidism Leukemia Gigantism Diabetes mellitus Muscular dystrophy Hyperthyroidism

  27. URINE CREATININE INCREASED BY DECREASED BY Ascorbic acid Anabolic steroids Captopril Methotrexate Thiazides Methyldopa Ketoprofen Cefoxitin

  28. CREATININE CLEARANCE • Rate at which creatinine is removed from the blood. • Useful measure of glomerular filtration rate excreting capacity of the kidney.

  29. Normal values; men : 90-140 ml/sec/m² women: 72-110 ml/sec/m²

  30. SCHWARTZ FORMULA crcl(ml/min) = k x ht in cm/scr(mg/dl) k = 0.45 ,infants < 1 year of age k = 0.55 ,children and adolescent females. k = 0.7, adolescent males.

  31. COCKCROFT-GAULT equation • CrCl = (140-age) x weight(kg) 72 x SCr (mg/dl) X 0.85

  32. CLINICAL IMPLICATIONS INCREASED State of high cardiac output pregnancy burns carbon monoxide poisoning DECREASED Impaired kidney function dehydration hemorrhage congestive heart failure

  33. INTERFERING FACTORS • Exercise may increase creatinine clearance and urine creatinine. • Pregnancy increases CrCl • Proteinuria and advanced renal failure make CrCl an unreliable method for determining GFR.

  34. BLOOD UREA NITROGEN • End product of protein metabolism (liver) • It travels through the blood and is excreted by the kidney. • BUN measures the amount of nitrogen in the blood in the form of urea.

  35. Normal value; Adults : 6-20 mg/dl Elderly patients : 8-23 mg/dl Children : 5-18 mg/dl AZOTEMIA; excessive retention of nitrogenous waste products. Renal azotemia ; renal disease (glomerulonephritis and chronic pyelonephritis). Prerenalazotemia; severe dehydration hemorrhagic shock excessive protein intake. Postrenalazotemia; urethral stones tumours prostatic obstructions.

  36. CLINICAL IMPLICATIONS • 1.Increased BUN levels (azotemia) a. impaired renal function congestive heart failure salt and water depletion stress acute MI b. chronic renal diseases c. Urinary tract obstruction d. hemorrhage into GI tract. e. diabetes mellitus • 2. Decreased BUN levels a. liver failure b. acromegaly c. malnutrition

  37. INTERFERING FATCORS • Decreased BUN levels late pregnancy combination of a low protein and high carbohydrate diet.

  38. BUN increased by BUN decreased by • ACE inhibitors • Indomethacin • Penicillin • Thiazides • Rifampin • Spironolactone • Cefotaxime • Phenothiazines • Chloramphenicol • Levodopa • Amikacin

  39. GLOMERULAR FILTRATION RATE • GFR is the volume of water filtered or cleared out of the plasma per minute. • GFR is approximated by measuring the urinary excretion rate of a marker substance. • Example for marker inulin.

  40. Normal value; Average GFR in young male adult: 120ml/min/1.73m²

  41. URINE PROTEINS • Increased amounts of protein is an important indicator of renal diseases. • Normal value; Adult male:10-140 mg/dl Female:30-100 mg/dl

  42. CLINICAL IMPLICATIONS • Proteinuria Glomerular damage Diminished tubular reabsorption Renal artery stenosis Tumours Renal transplant rejection

  43. INCREASED BY • Mefenamic acid • Theophylline • Penicillin • Furosemide • Carbamazepine

  44. URINE GLUCOSE • Present in glomerular filtrate and is reabsorbed by the PCT. • Blood glucose level >reabsorption capacity glucose

  45. Normal values; • Random specimen : negative • 24-hour specimen :1-15 mg/dl

  46. CLINICAL IMPLICATIONS Increased glucose diabetes mellitus liver and pancreatic disease endocrine disorders impaired tubular reabsorption Increase of other sugars Lactose - pregnancy,lactation Xylose - excessive ingestion of fruit

  47. URINE GLUCOSE • Increased by Chlorpromazine Phenytoin Sulfonamide Tetracycline • Decreased by Ampicillin Insulin Carvidopa Furosemide

  48. URINE SODIUM • Helps to regulate acid-base balance. • Normal value; adult : 40-220 mEq/24 hours child : 41-115 mEq/24 hours

  49. CLINICAL IMPLICATIONS • Increased sodium Adrenal failure Renal tubular acidosis Diabetic acidosis • Decreased sodium Excessive sweating Congestive heart failure Cushing’s disease

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