Description

Renal failure, also called kidney failure, is classified based on duration, underlying cause, and severity. Here’s a breakdown of the main classifications: 1. Based on Duration (Temporal Course) A. Acute Kidney Injury (AKI) Sudden decline in kidney function (hours to days). Reversible if treated promptly. Diagnostic Criteria: ↑ Serum creatinine by ≥0.3 mg/dL within 48 hours or ↑ Serum creatinine to ≥1.5× baseline within 7 days or Urine output <0.5 mL/kg/h for 6+ hours. Stages (KDIGO Criteria): Stage 1: Cr 1.5–1.9× baseline or ↑ ≥0.3 mg/dL; UO <0.5 mL/kg/h for 6–12h. Stage 2: Cr 2.0–2.9× baseline; UO <0.5 mL/kg/h for ≥12h. Stage 3: Cr 3× baseline or ≥4.0 mg/dL (or initiation of dialysis); UO <0.3 mL/kg/h for ≥24h or anuria ≥12h. B. Chronic Kidney Disease (CKD) Progressive, irreversible loss of kidney function over ≥3 months. Stages (KDIGO) based on GFR: G1: Normal GFR (≥90 mL/min) but with kidney damage (e.g., proteinuria). G2: Mild ↓ GFR (60–89). G3a: Mild-moderate ↓ GFR (45–59). G3b: Moderate-severe ↓ GFR (30–44). G4: Severe ↓ GFR (15–29). G5: Kidney failure (GFR <15 or dialysis). C. Acute-on-Chronic Kidney Disease (AoCKD) Sudden worsening of pre-existing CKD (e.g., due to dehydration, nephrotoxins). 2. Based on Underlying Cause A. Prerenal (↓ Kidney Perfusion) Causes: Hypovolemia (dehydration, bleeding), hypotension, heart failure, renal artery stenosis. Lab Findings: ↑ BUN/Cr ratio (>20:1), bland urine sediment. B. Intrinsic Renal (Kidney Tissue Damage) Subtypes: Acute Tubular Necrosis (ATN) – Most common (ischemia, toxins like NSAIDs, contrast). Glomerulonephritis (e.g., IgA nephropathy, lupus nephritis). Interstitial Nephritis (drug-induced, infections). Vascular Causes (vasculitis, thrombotic microangiopathy). C. Postrenal (Urinary Tract Obstruction) Causes: BPH, kidney stones, tumors, urethral stricture. Diagnosis: Hydronephrosis on ultrasound, sudden anuria. 3. Based on Severity (for CKD) Mild (Stages G1–G3a): Often asymptomatic. Moderate-Severe (Stages G3b–G4): Fatigue, edema, hypertension. End-Stage Renal Disease (ESRD, Stage G5): Requires dialysis or transplant.

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