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Key Features

Essentials of Diagnosis

  • Rapid increase in serum creatinine

  • Oliguria may be present

  • Symptoms and signs depend on cause

General Considerations

  • Defined as an absolute increase in serum creatinine by ≥ 0.3 mg/dL within 48 hours or relative increase to ≥ 1.5 times baseline that is known or presumed to have occurred within 7 days

  • Characterized as oliguric if urine production is < 400–500 mL/day or < 20 mL/h

  • Clinically, characterized by an inability to maintain acid-base, fluid, and electrolyte balance and to excrete nitrogenous wastes

  • The 2012 KDIGO Clinical Practice Guidelines for AKI describes three progressive stages based on the elevation in serum creatinine or decline in urinary output

    • Stage 1: 1.5- to 1.9-fold increase in serum creatinine or a decline in urinary output to 0.5 mL/kg/h over 6–12 hours

    • Stage 2: 2.0–2.9 increase in serum creatinine or a decline in urinary output to 0.5 mL/kg/h over > 12 hours

    • Stage 3: 3-fold or greater increase in serum creatinine, an increase in serum creatinine to ≥ 4 mg/dL, or a decline in urinary output to < 0.3 mL/kg/h for ≥ 24 hours, anuria for ≥ 12 hours, or initiation of renal replacement therapy

  • Serum creatinine concentration can typically increase by 1.0–1.5 mg/dL daily

Demographics

  • 5% of hospital admissions and 30% of ICU admissions have acute kidney injury

  • 25% of hospitalized patients develop acute kidney injury

Clinical Findings

Symptoms and Signs

  • Nausea, vomiting

  • Malaise

  • Hypertension

  • Pericardial friction rub, effusions, and cardiac tamponade

  • Arrhythmias

  • Rales

  • Abdominal pain and ileus

  • Bleeding secondary to platelet dysfunction

  • Encephalopathy, altered sensorium, asterixis, seizures

  • Oliguria, defined as urinary output < 500 mL/day or < 20 mL/h

Differential Diagnosis

PRERENAL CAUSES

  • Dehydration

  • Hemorrhage (eg, gastrointestinal bleeding)

  • Heart failure

  • Renal artery stenosis, including fibromuscular dysplasia

  • Nonsteroidal anti-inflammatory drugs (NSAIDs), angiotensin-converting enzyme inhibitors

POSTRENAL CAUSES

  • Obstruction (eg, benign prostatic hyperplasia, bladder tumor)

INTRINSIC RENAL DISEASE

  • Acute tubular necrosis

    • Toxins

      • NSAIDs

      • Antibiotics

      • Intravenous contrast

      • Plasma cell myeloma (formerly multiple myeloma)

      • Rhabdomyolysis

      • Hemolysis

      • Chemotherapy

      • Hyperuricemia

      • Cyclosporine

    • Ischemia (eg, prolonged prerenal insults)

  • Acute glomerulonephritis

    • Immune complex

      • IgA nephropathy

      • Endocarditis

      • Systemic lupus erythematosus (SLE)

      • Cryoglobulinemia

      • Postinfectious

      • Membranoproliferative

    • Pauci-immune (ANCA-positive)

      • Granulomatosis with polyangiitis (formerly Wegener granulomatosis)

      • Eosinophilic granulomatosis with polyangiitis (formerly Churg-Strauss syndrome)

      • Microscopic polyarteritis

    • Antiglomerular basement membrane (anti-GBM)

      • Goodpasture disease

      • Anti-GBM glomerulonephritis

  • Vascular

    • Malignant hypertension

    • Thrombotic thrombocytopenia purpura

    • Atheroembolism

  • Acute interstitial nephritis

    • Drugs

      • β-Lactams

      • Sulfa

      • Diuretics

      • NSAIDs

      • Rifampin

      • Phenytoin

      • Allopurinol

    • Infections

      • Streptococcus

      • Leptospirosis

      • Cytomegalovirus

      • Histoplasmosis

      • Rocky Mountain spotted fever

    • Immune

      • SLE

      • Sjögren syndrome

      • Sarcoidosis

      • Cryoglobulinemia

Diagnosis

Laboratory Tests

  • Serum creatinine and BUN elevated

  • BUN–creatinine ratio > 20:1 in prerenal and postrenal causes, and acute glomerulonephritis; < 20:1 in acute tubular necrosis and ...

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