Renal function tests
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Transcript of 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
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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