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;
|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:
|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.