Acute Renal Failure

• ARF is the condition when kidney suddenly fails to excrete water,electrolytes & waste products.

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

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

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

Causes of CRF

• Chronic nephritis• Hypertension• Renal stones• Development of cyst in kidney• Atherosclerosis• Slow poisoning

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

• Acidosis• Hyperkalemia• Edema• Anemia• Hyperparathyroidism-is developed due to

deficiency of 1,25 di-OHCCF.This causes removal of calcium from bones causing osteomalacia

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

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

RENAL FUNCTION TESTS

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

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

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.

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

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.)

4) Odour> mild aromatic volatile org. acids

Unpleasant ammoniacal (prolonged standing)

Acidotic fruity (DKA)

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)

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

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.

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

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

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

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)

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.

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

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

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

• Correlated more directly with the status of kidney function employed to assess GFR,RPF & RBF

Renal clearance TESTS:

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)

** 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.

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.