all about RFT tests

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

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

8. 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

9.  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

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

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

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

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

14. 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

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

16. 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.

17. 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

18. 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

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

20. 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).

21. 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

22. INTERFERING FACTORS
 alkaline urine
Sodium bicarbonate
potassium citrate
acetazolamide
 acidic urine
ammonium chloride
mandelic acid

23. 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

24.  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

25. CLINICAL IMPLICATIONS
 SERUM CREATININE
increased in;
ingestion of roast meat
muscle disease
prerenal azotemia
postrenal azotemia
decreased in;
pregnancy

26. SERUM CREATININE
INCREASED BY DECREASED
BY
ACE inhibitors Ascorbic
acid
Alprazolam Captopril
Aspirin Dopamine
Cefixime Valproic
acid
Methotrexate
Prednisone
Ranitidine
Triamterene
Ibuprofen

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

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

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

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

31. 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.

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

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

34. 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.

35. 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.

36.  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.

37. 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

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

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

40. 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.

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

42. 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

43. CLINICAL IMPLICATIONS
 Proteinuria
Glomerular damage
Diminished tubular reabsorption
Renal artery stenosis
Tumours
Renal transplant rejection

44. INCREASED BY
 Mefenamic acid
 Theophylline
 Penicillin
 Furosemide
 Carbamazepine

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

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

47. 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

48. URINE GLUCOSE
 Increased by
Chlorpromazine
Phenytoin
Sulfonamide
Tetracycline
 Decreased by
Ampicillin
Insulin
Carvidopa
Furosemide

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

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

51. SODIUM IN URINE
 Verapamil
 Clofibrate
 Aspirin
 atenolol
 Omeprazole
 Propranolol
 lithium
 INCREASED BY  DECREASED BY

52. URINE POTASSIUM
 Vital function in the body’s overall
electrolyte balance.
normal;
adult : 25-125 mEq/24 hours
child : 10-60 mEq/24 hours

53. CLINICAL IMPLICATIONS
 Primary renal
disease
 Starvation
 Diabetic and renal
tubule acidosis
 Cushing’s
syndrome
 Addison’s disease
 Severe renal
disease
 INCREASED
POTASSIUM
 DECREASED
POTASSIUM

54. POTASSIUM IN URINE
 Oral contraceptives
 Chlorthalidone
 Antibiotics
 Isosorbide
 Diuretics
 Anesthetic agents
 Ketoconazole
 Trimethoprim
 INCREASED BY  DECREASED BY

55. URINE CHLORIDE
 Diagnose 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

56. CLINICAL IMPLICATIONS
 Increased salt intake
 Adrenocortical
insufficiency
 Potassium depletion
 Vomiting,diarrhoea
 Gastric suction
 Addison’s disease
 Cushing’s syndrome
 Conn’s syndrome
 INCREASED
CHLORIDE
 DECREASED
CHLORIDE

57. 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

58. URINE KETONES
 From fatty acid and fat.
 Consists mainly of three substances
: acetone,
β-hydroxybutyric acid
acetoacetic acid.
normal value;
urine: negative (<0.3 mg/dl)

59. CLINICAL IMPLICATIONS
 Hyperthyroidism
 Fever
 Pregnancy or
lactation
 Diabetes mellitus
 Starvation
 Anorexia
 INCREASED
METABOLIC STATES
 DECREASED
METABOLIC
STATES

60. KETONES IN URINE
 Amino salicylic acid
 Cefixime
 Valproic acid
 Captopril
 Aspirin
 Phenazopyridine
 INCREASED BY  DECREASED BY

61. MACROSCOPIC EXAMINATION
of centrifuged urine.
 1) Hematuria
it indicates trauma, tumour, systemic
bleeding.
 2) casts
Casts are cylindrical elements with
parallel sides

62. HYALINE CASTS
Particularly in dehydration

63. RED CELL CASTS
 Glomerulonephritis

64. WHITE CELL CAST
 Pyelonephritis

65. GRANULAR CASTS
 Renal parenchymal disease
 Dehydration

66. EPITHELIAL CAST
 Tubular damage

67. EXOGENOUS MARKERS
 INULIN CLEARANCE
normal value;
men : 127ml/min/m²
women: 118ml/min/m²
 Fructose polysaccharide.
 Patient receives inulin to achieve a steady
blood concentration.
 The quantity in plasma and the amount
excreted in urine is measured.