DR. SAMI ABDO RADMAN

Acute Renal Failure

Acute Renal Failure Definition Acute renal failure (ARF) is a syndrome defined as an abrupt decrease in glomerular filtration rate sufficient to result in retention of nitrogenous waste products (blood urea nitrogen [BUN] and creatinine) and perturbation of extracellular fluid volume and electrolyte and acid-base homeostasis

Usually, but not invariably, reversible over a period of days or weeks.

Detsufficiently severe to result in uraemia

Oliguria is usually, but not invariably, a feature.

Cause sudden, life-threatening biochemical erioration in renal function is disturbances

Is a medical emergency..

Causes ARF can result from (1) diseases that cause a decrease of

renal blood flow (prerenal azotemia ( (2diseases that directly involve renal

parenchyma (renal azotemia) (3) diseases associated with urinary

tract obstruction (postrenal azotemia)

Prerenal uraemia

Is the most common form of ARF There is impaired perfusion of the kidneys

with blood. Hypovolaemia, Hypotension, Impaired cardiac pump efficiency or Vascular disease limiting renal blood flow, Or combinations of these factorsExcretory function in prerenal uraemia

improves once normal renal perfusion has been restored.

CLINICAL MANIFESTATIONS

Thirst, dizziness Hypotension and tachycardia, Reduced jugular venous pressure,Decreased skin turgor, Dry mucous membranes,Reduced axillary sweating.History of intake of hypotensive drugs

Management

Correction of hypovolaemia and hypotension,

Treatment of the undelying cause

recovery typically takes 1 to 2 weeks after normalization of renal perfusion

Postrenal uraemia

Obstruction of the urinary tract at any point from the calyces to the external urethral orifice.

Clinical exam:Tenderness on the suprabubic region or renal

angle History of stones History of Prostatic diseaseTreatment Removal of the obstruction

Renal AzotemiaAcute uraemia due to renal parenchymal disease (Acute tubular necrosis, ATN)

This is most commonly due to acute renal tubular necrosis (Due to acute ischemic or nephrotoxic insult)

Causes HaemorrhageBurnsDiarrhoea and vomitingDiureticsMyocardial infarction

Congestive cardiac failureSnake biteMyoglobinaemia Haemoglobinaemia (due to haemolysis, e.g. in falciparum malaria, 'blackwater fever)

Hepatorenal syndrome Drugs, e.g. aminoglycosides, NSAIDs, ACE inhibitors

N.B:In liver failure, acute renal result from rapidly

reversible vasomotor abnormalities within the kidney.

A kidney removed from a patient with hepatic cirrhosis and liver failure dying with oliguric renal failure may function normally immediately after transplantation into a normal individual

Pathogenesis Intrarenal microvascular vasoconstriction:

Tubular cell injury Ischaemic injury results in rapid depletion of intracellular ATP stores resulting in cell death

Glomerular contraction reducing the surface area available for filtration

Obstruction of the tubule by debris shed from ischaemic tubular cells

Clinical Course Depending on the severity and duration

of the renal insult. Oliguria is common in the early stages:

non-oliguric renal failure is usually a result of a less severe renal insult.

Recovery of renal function typically occurs after 7-21 days,

ATN may last for up to 6 weeks, even after a relatively short-lived initial insult

Clinical and biochemical featuresThe features of the causal condition together with features of rapidly progressive uraemia

serum urea and creatinine concentrations depend upon the rate of tissue breakdown(trauma, sepsis and surgery)

Pulmonary oedema

Symptoms of uraemia such as anorexia, nausea, vomiting pruritus develop, drowsiness, fits, coma and haemorrhagic

episodes. Epistaxes and gastrointestinal

haemorrhage Severe infection may have initiated the

acute renal failure or have complicated it owing to the ( impaired immune defences)

URINALYSIS in ARFAnuria suggests complete urinary tract

obstruction OR severe cases of prerenal or intrinsic renal ARF

Wide fluctuations in urine output raise the possibility of intermittent obstruction,

Polyuria in partial urinary tract obstructionTransparent hyaline casts In prerenal ARF, (secreted by epithelial cells of the loop of

Henle)

Hematuria and pyuria are common in patients with intraluminal obstruction or prostatic disease.

Epithelial casts present in ATN (ischemic or nephrotoxic ARF)

Red blood cell casts indicate glomerular injury

Eosinophiluria is common in antibiotic-induced allergic interstitial nephritis

Bilirubinuria may provide a clue to the presence of hepatorenal syndrome.

Urine should be tested for free haemoglobin and myoglobin,

Laboratory findings in ARFBlood tests include measurement of

serum urea, electrolytes, creatinine, calcium, phosphate, albumin,

Increase serum Creatinin Hyperkalemia, hyperphosphatemia,

hypocalcemiaSevere anemia in the absence of

hemorrhage indicates hemolysisSystemic eosinophilia suggests

allergic interstitial nephritis

RADIOLOGICAL INVESTIGATIONSA plain film of the abdomen UltrasonographyPelvicalyceal dilatation is usual with urinary tract obstruction

Retrograde or anterograde pyelography

ManagementGeneral measures

Consistent documentation of fluid intake and output,

Measurement of daily bodyweightEmergency measures

Correction of acidosis with intravenous sodium bicarbonate

Pulmonary oedema DuireticsTreatment of sepsis

Fluid and electrolyte balance Diet

Protien restriction (40 gm daily)sodium and potassium restriction

Management …contDialysis is indicated in

Symptoms of uraemia Complications of uraemia, such as

pericarditis Hyperkalaemia not controlled by

conservative measures Pulmonary oedema Severe acidosis For removal of drugs causing the acute renal

failure, e.g. Gentamicin, lithium, severe aspirin overdose.