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

TUBULAR REABSORPTION

TUBULAR SECRETION

RATE OF URINARY EXCRETION OF ANY SOLUTE

= RATE OF GLOMERULAR

FILTRATION + RATE OF SECRETION - RATE OF REABSORPTION

PHYSICAL TESTS

i. URINE VOLUME Assessment of fluid balance and kidney

function. Normal value; adult : 800-2500 mL/day children : 500-1400 mL/day

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

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

INTERFERING FACTORS

1.polyuria a)intravenous glucose or saline b)thiazides c)coffee,alcohol,tea,caffeine

2.oliguria a)dehydration b)excessive salt intake

2.URINE COLOUR

Yellow colour due to urochrome.

Normal; Pale yellow to amber Straw colour- low SG Amber colour-high SG

CLINICAL IMPLICATIONSAlmost colourless urine; large fluid intake chronic interstitial nephritis untreated diabetes mellitus diabetes insipidus alcohol and caffeine ingestion diuretic therapy nervousnessOrange colour; fever carrots or vitamin A phenazopyridine, nitrofurantoin

Green urine; pseudomonal infection chlorophyllRed urine RBCs haemoglobin myoglobin porphyrinsBlack urine melanin phenol poisoningSmoky urine - RBCsMilky urine - fat,cystinuria,WBCs

INTERFERING FACTORSColour darkens on standing 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

3.URINE ODOUR

Faint odour owing to the presence of volatile oils.

normal; aromatic odour.

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.

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

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

INTERFERING FACTORS

Elevated readings Moderate amounts of protein Patients receiving intravenous

albumin. Diuretics and antibiotics

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).

CLINICAL IMPLICATIONS1. 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

INTERFERING FACTORSalkaline urine Sodium bicarbonate potassium citrate acetazolamide

acidic urine ammonium chloride mandelic acid

CHEMICAL EXAMINATION OF URINE

ENDOGENOUS MARKERS

a) SERUM CREATININE (kreas)

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

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

CLINICAL IMPLICATIONSSERUM CREATININE increased in; ingestion of roast meat muscle disease prerenal azotemia postrenal azotemia decreased in; pregnancy

SERUM CREATININE INCREASED BY DECREASED BY ACE inhibitors Ascorbic acid Alprazolam Captopril

Aspirin Dopamine Cefixime Valproic acid Methotrexate Prednisone Ranitidine Triamterene Ibuprofen

CLINICAL IMPLICATIONSURINE CREATININE

Increased by decreased by

Acromegaly Anemia Hypothyroidism Leukemia Gigantism Diabetes mellitus Muscular dystrophy Hyperthyroidism

URINE CREATININE INCREASED BY DECREASED BY Ascorbic acid Anabolic

steroids Corticosteroids Captopril Methotrexate Thiazides Methyldopa Ketoprofen Cefoxitin

CREATININE CLEARANCE

Rate at which creatinine is removed from the blood.

Useful measure of glomerular filtration rate excreting capacity of the

kidney.

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

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.

COCKCROFT-GAULT equation

CrCl = (140-age) x weight(kg) 72 x SCr (mg/dl)

X 0.85

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

INTERFERING FACTORSExercise may increase creatinine

clearance and urine creatinine.

Pregnancy increases CrCl

Proteinuria and advanced renal failure make CrCl an unreliable method for determining GFR.

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.

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).Prerenal azotemia; severe dehydration hemorrhagic shock excessive protein intake.Postrenal azotemia; urethral stones tumours prostatic obstructions.

CLINICAL IMPLICATIONS1.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

INTERFERING FATCORS

Decreased BUN levels late pregnancy combination of a low protein

and high carbohydrate diet.

ACE inhibitorsIndomethacinPenicillinThiazidesRifampinSpironolactoneTimolol

CefotaximePhenothiazinesChloramphenicolLevodopaAmikacin

• BUN increased by

BUN decreased by

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.

Normal value; Average GFR in young male

adult:

120ml/min/1.73m²

URINE PROTEINSIncreased amounts of protein is

an important indicator of renal diseases.

Normal value; Adult male:10-140 mg/dl Female:30-100 mg/dl

CLINICAL IMPLICATIONSProteinuria

Glomerular damage Diminished tubular

reabsorption Renal artery stenosis Tumours Renal transplant rejection

INCREASED BY Mefenamic acidTheophyllinePenicillinFurosemideCarbamazepine

URINE GLUCOSE

Present in glomerular filtrate and is reabsorbed by the PCT.

Blood glucose level >reabsorption capacity

glucose

Normal values;

Random specimen : negative24-hour specimen :1-15 mg/dl

CLINICAL IMPLICATIONS

Increased glucose diabetes mellitus liver and pancreatic disease endocrine disorders impaired tubular reabsorption

Increase of other sugarsLactose - pregnancy,lactationXylose - excessive ingestion of fruit

URINE GLUCOSEIncreased by Chlorpromazine Phenytoin Ofloxacin Sulfonamide Tetracycline

Decreased by Ampicillin Insulin Carvidopa Furosemide

URINE SODIUM

Helps to regulate acid-base balance.

Normal value; adult : 40-220 mEq/24 hours child : 41-115 mEq/24 hours

CLINICAL IMPLICATIONS

Increased sodium

Adrenal failure Renal tubular acidosis Diabetic acidosis

Decreased sodium

Excessive

sweating Congestive heart failure Cushing’s

disease

SODIUM IN URINE

VerapamilClofibrateAspirinatenolol

OmeprazolePropranololRamiprillithium

INCREASED BY DECREASED BY

URINE POTASSIUM

Vital function in the body’s overall electrolyte balance.

normal; adult : 25-125 mEq/24 hours child : 10-60 mEq/24 hours

CLINICAL IMPLICATIONS

Primary renal disease

StarvationDiabetic and

renal tubule acidosis

Cushing’s syndrome

Addison’s disease

Severe renal disease

INCREASED POTASSIUM

DECREASED POTASSIUM

POTASSIUM IN URINE

Oral contraceptives

ChlorthalidoneAntibioticsIsosorbideDiuretics

Anesthetic agents

FelodipineKetoconazoleTrimethoprimRamipril

INCREASED BY DECREASED BY

URINE CHLORIDEDiagnose dehydration or as a guide

in adjusting fluid and electrolyte balance.

Also useful in monitoring the effects of reduced salt diets( CVD,HTN)

Normal value; adult: 140-250 mEq/24 hours child : 64-176 mEq/24 hours

CLINICAL IMPLICATIONS

Increased salt intake

Adrenocortical insufficiency

Potassium depletion

Vomiting,diarrhoea

Gastric suctionAddison’s

diseaseCushing’s

syndromeConn’s syndrome

INCREASED CHLORIDE

DECREASED CHLORIDE

URINE CHLORIDE

Ammonium chloride administration

Excessive infusion of normal saline

Ingestion of sulfides, cyanides, halogens, bromides and sulfhydril compounds.

Carbenicillin therapy

Reduced dietary intake of chloride

Ingestion of large amounts of licorice

Alkali ingestion

Dehydration

INCREASED CHLORIDE

DECREASED CHLORIDE

URINE KETONESFrom fatty acid and fat.Consists mainly of three substances : acetone, β-hydroxybutyric

acid acetoacetic acid. normal value; urine: negative (<0.3

mg/dl)

CLINICAL IMPLICATIONS

HyperthyroidismFeverPregnancy or

lactation

Diabetes mellitusStarvationAnorexia

INCREASED METABOLIC STATES

DECREASED METABOLIC STATES

KETONES IN URINE

Amino salicylic acid

CefiximeValproic acidDimercaprolCaptopril

AspirinPhenazopyridine

INCREASED BY DECREASED BY

MACROSCOPIC EXAMINATION of centrifuged urine.

1) Hematuria it indicates trauma, tumour,

systemic

bleeding.2) casts

Casts are cylindrical elements with parallel sides

HYALINE CASTS

Particularly in dehydration

RED CELL CASTS

Glomerulonephritis

WHITE CELL CASTPyelonephritis

GRANULAR CASTSRenal parenchymal diseaseDehydration

EPITHELIAL CAST Tubular damage

EXOGENOUS MARKERSINULIN CLEARANCE normal value; men : 127ml/min/m² women: 118ml/min/m²Fructose polysaccharide.

Patient receives inulin to achieve a steady blood concentration.

The quantity in plasma and the amount excreted in urine is measured.

IOTHALAMATE

Normal value; men : 127 ml/min/m² women: 118 ml/min/m²

Injection of the radioactive exogenous marker .

These are not widely used.

REFERENCESA manual of laboratory and diagnostic

tests; by Frances Fischbach, Marshall B.Dunning, Edition 8.

Textbook of therapeutics; Drug and disease management by Eric.T.Herfindal,sixth edition.

Comprehensive pharmacy review by Leon shargel,fourth edition.

Basic skills in interpreting laboratory data by Mary Lee,fourth edition.

Principles of anaatomy and physiology by Tortora, tenth edition.

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