renal function tests
DESCRIPTION
Acute renal failure,chronic renal failure,Kidney function tests.TRANSCRIPT
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Acute Renal Failure
• ARF is the condition when kidney suddenly fails to excrete water,electrolytes & waste products.
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Causes of ARF
• Acute nephritis- immune complex• Damage to renal tissue by poisons like
lead,mercury & carbon-tetrachloride• Renal ischemia which is developed during
ciculatory shock• Severe transfusions reactions• Sudden fall in B.P. during
haemorrhage,dirrhoea,severe burn,cholera• Blockage of ureter due to formation of calculi
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Symptoms
• Volume of urine out put is reduced (oligouria) & in severe condition –Anuria(stopage of urine formation)
• Proteins +++ urine(proteinuria)-albumin++• RBC,WBC & casts +++urine• Retention of Na & water- edema, ECFV• Hypertension• Acidosis• If the Patient is not treated in time ,the acidosis
becomes severe resulting in coma & death within 10 to 15 days
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Chronic Renal Failure
• When some of the nephrons loose function the unaffected nephrons can perform the functions.
• However when more & more nephrons starts loosing the function over the months or years,the CRF is developed
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Causes of CRF
• Chronic nephritis• Hypertension• Renal stones• Development of cyst in kidney• Atherosclerosis• Slow poisoning
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Symptoms• Excessive accumulation of metabolic end
products like urea,creatinine in blood is called Uremia.
• Common features of uremia are• Loss of appetite(anorexia) ,Lethargy• Drowsiness ,Nausea& vomiting• Pigmentation of skin,mascular twiching• Convulsions,confusion & mental deterioration
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• Acidosis• Hyperkalemia• Edema• Anemia• Hyperparathyroidism-is developed due to
deficiency of 1,25 di-OHCCF.This causes removal of calcium from bones causing osteomalacia
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Dialysis
• In physiologic sense refers to diffussion of solutes from an area of higher conc. To the area of lower conc.through a semi-permeable membrane.
• This principal has been used to dialyse the blood of patients with renal failure specially those developing Uremia.
• Uremia develops>70% nephrons damaged
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Haemodilysis
• Intermittent dialysis may prolonge the life of many patients with CRF.
• it can partially replace excretory function of the kidneys but does not replace endocrine & metabolic functions
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RENAL FUNCTION TESTS
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FUNCTIONS of KIDNEY :1) Excretory – primary :by urine formation
2) Regulation of volume & electrolyte composition of ECF
3) Regulation of acid-base balance
4) Endocrine function – produce & secrete: erythropoietin, renin, calcitriol(1,25-DHCC)
5) Site of neoglucogenesis – not primary: in starvations- esp. from glutamine
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Renal Function Tests :
collective term for a variety of individual tests and procedures that can be done to evaluate how well the kidneys are functioning.
Practically, divided into 3 groups –1) Analysis of urine & blood2) Specific assessment of renal clearance3) Additional special Tests
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OBJECTIVES of RFT : Early detection of possible renal damage &
assessment of its severity Measure progression of the renal impairment &
efficacy of corrective therapy Predict when renal replacement therapy may
be necessary Monitor safe & effective use of drugs, which
are principally eliminated through urine.
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ANALYSIS OF URINE :
A) PHYSICAL :1)Volume 1000-2500 ml/d Normal Polyuria >2.5L/d Chronic GN Oliguria<400ml/d seen in Ac GN,
Terminal RF• Anuria <100ml/d seen in Renal Failure
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2) Appearance > clear Turbid (alkalinity d/t prolonged
standing l/t ppt of Ca/Mg-phosphates,↑phosphate , presence of pus d/t UTI)
3) Colour> straw/amber-yellow urochromeBrownish yellow (jaundice)Dark (alkaptonuria)Reddish brown (RBC/Hb/Mb-uria,Porphyria etc.)
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4) Odour> mild aromatic volatile org. acids
Unpleasant ammoniacal (prolonged standing)
Acidotic fruity (DKA)
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5) Sp. Gravivity & Osmolality > 1.003 to 1.030 & 50-1200 mOsm/kg (depends
on state of hydration of the body)
Early morning urine sample(=after overnight fast)if SG>1.018 & Osm>600 ≡Normal
SG is simplest to measure but unreliable(in presence of HMW substances) for evaluating renal concentrating ability.
SG decreased,increased & fixed(1.010=CRF)
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Applied aspect
• 12 hr water deprivation results in S.G. of urine to become 1025 with 1000 osmolarity. Failure to do this indicate abnormal renal functioning
• in S.G. is seen in =• low water intake, DM, Albuminuria,Ac Nephritis• In S.G. is seen in=• Tubular Damage, Absence of ADH
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B) BIOCHEMICAL :
1) Reaction > mild acidic pH avg.6 (=4.5-7.5)
normal short PP alkaline tide Protein rich diet acidic Vegetable rich diet alkaline also in
type II DTA, UTI by urease producing organisms, Acetazolamide therapy, alkali ingestion.
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2) For abnormal urinary constituents :
I) Proteins > Normal upto 150 mg/d—routinely
undetected Proteinuria >150mg/d albumin
predominates Glomerulonephritis,
Pyelonephritis,Toxaemia of pregnancy, tubulo-interstial disorders
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II) Reducing Sugars > Normally absent –
glucose/fructose/galactose
++ DM,Renal Glycosuria,Alimentary Glycosuria
Fructose,Galactose++in Metabolic disorders
III) Blood >Haematuria Normally does not appear ++ Ac GN,Renal stones,Malignancy of UT
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IV) Ketone Bodies > Normally not present ++Prolonged starvation,Diabetic Ketoacidosis
V) Bile salts > Only in early phases of obstructive
jaundice By- Hay’s test & Petenkoffer’s test
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VI) Urobilinogen > N ~1 - 3.5 mg/d ↑ in persistent fevers, hepatobiliary diseases,
haemolytic jaundice
VII) Bile-pigments > Bilirubinuria=↑conj.Bilirubin hep/post-hep jaun VIII) Haemoglobinuria Normally =absent ++indicate intravascular Haemolysis(Black water fever
due to falciperum malaria)
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C) MICROSCOPIC :Imp findings in the urinary sediment includes---
I) Casts >> proteinaceous plugs Formation favoured by sluggish flow Various shapes c/t tubules in which
formed cellular or non-cellular Types Hyaline, RBC, WBC,
Granular, Broad waxy etc.
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II) Crystals >> Ca-oxalate/phosphate, Triple phosphate--
common May be normally found risk of stone in future Urate or Cysteine crystals pathologic
III) Cells >> RBCs, WBCs, pus cells, Sq.epithelial, Tubular
epithelial cells
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ANALYSIS of Blood : There is no plasma constituent whose conc. depends solely on
the functionality of kidneys. Frequently used are 2 normal metabolic wastesExcreted by kidneys accumulates in renal dysfunction
↑blood levels
I) Blood Urea = 20-40 mg% begin to rise only after 50% renal damage
II) Plasma Creatinine >> 0.6 – 1.5 mg% More reliable as blood ureaq is subjected to variations• Serum K+ =5mEq/L increased in oligoruria
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Renal clearance TESTS:Vol. of plasma that is cleared of a substance in
unit time, by its’ urinary excretion ml/minCalculated as: C = UV/PPredominantly determine GFR: Relationship
as—GFR = C No reabs, No Secret INULIN
GFR > C Much reabs, No Secret Gluc, AA, Na+, Cl-
GFR < C No reabs, Much Secret PAH, Diodrast
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• Correlated more directly with the status of kidney function employed to assess GFR,RPF & RBF
Renal clearance TESTS:
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Various markers used :A) Exogenous >>1) Inulin (gold standard but technically
demanding)2) Non-radiolabelled contrast media (e.g.
Iohexol) 3) Radiolabelled compounds (e.g. 99m Tc-
DTPA)B) Endogenous >>4) Creatinine (marginally overestimates—
most widely used in clinical practice)5) Urea (one of the 1st markers– not used at
present)
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** Prediction of GFR from Plasma creatinine levels:
Approximation of bedside GFR with limited accuracy by “Cockroft & Gault formula”
Most widely used & best validated for adultsCcr =(140-Age)x(Wt in Kg)/(Plasma Creatinine x72) [Correction factor for females = 0.85]value to such formulas for GFR prediction is likely to
increase when an accurate plasma creatinine assay is performed along with inhibition of tubular secretion by cimetidine/probenecid.
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Renal Imaging studies >>
Plain radiograph of abdomenIVPUSG, CT Scan, MRI ScanRadionuclide studies
Strictly speaking, these are not considered to be RFTs, but very useful in present day clinical practice for structural & functional assessment of kidneys.