Introduction to Acute Kidney Injury



Intro: also known as acute renal failure is characterized by rapid loss (within 48 hours) of excretory function of kidneys having raised SrCr and urea concentration. Patients could   n = be normouric, oligouric (urine output decreases to <400ml/day) or anuric.

Classification: according to risk, injury, failure, loss and end stage kidney disease (RIFLE) classification is  based upon SrCr and urine output.  3 stages are;

Stage GFR Urine output
1: Risk         SrCr increases to 1.5-2 times baseline or GFR decreases to <25% <0.5ml/kg/h in<6 hrs
2: Injury Scr increased to 2-3 times or GFr <50% <0.5ml/kg/h in>12  hrs
3: Failure Scr >3 times baseline or GFR 75% 0.3ml/kg/h over 24 hrs or anuria lasting >12 hrs


Causes: causes are divided into 3 categories:

Cause Processes/subgroup Examples
Pre-renal a.    Intrarenal vasoconstriction Drugs like anti BP, cyclosporine, diuretics, laxatives, NSAIDs, vasoconstrictors, tacrolimus
b.    Systemic vasodilation Sepsis, neurogenic shock
c.     Volume depletion Diuretic overuse, osmotic diuresis, vomiting, diarrhea, burns, blood loss, sweating
Intrinsic a.     Glomerular Drugs… allopurinol, chloropamide, dapsone, gold, halothane, NSAIDs, hydrazaline, penicillin, rifampicin, thiazides, tolbutamide
b.    Interstitial Allopurinol, acyclovir, cephalosporins, cimetidine, cotrimoxazole, furosemide, interferon, Li, phenytoin, PPIs.

Infections and lupus

c.     Tubular  prolonged hypotension, nephrotoxic drugs, TLS, hemolysis, rhabdomylosis, myeloma.
d.    Vascular Renal vein thrombosis, malignant hypertension, renal infarct.
Post-renal a.     Ureteral / bladder BPH, cancer
b.    Pelvic Carcinoma, pelvic malignancies.
c.     Intra renal obstructions Stones, crystals, clots, tumors, paraproteins.


Clinical Presentation:  may vary from mild-moderate –asymptomatic and can only be detected by laboratory testing.  Severe cases present with confusion, edema, fatigue, anorexia, nausea, vomiting, hypertension, anuria, oligouria and hyperkalemia. Other problems caused could enlist uremic encephalopathy, anemia, bleeding due to uremic platelet dysfunction.

 Management:  at mild cases, ensure adequate renal perfusion by maintaining hemodynamic stability and avoiding hypovolemia. Nephrotoxic insults need to be removed via dialysis or adsorption. Care is to be given to nephrotoxic medications.

Fluid resuscitation in patients with intravascular volume depression is done by isotonic solutions not hyper, with an aim of keeping MAP at >65mmHg. Alternative is vasopressors use.  Low dose Dopamine has resulted in poor outcomes thus leading to its removal from the recommendations.


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