A 4-year-old boy develops bloody diarrhea after eating undercooked hamburgers. Five days later he becomes pale and oliguric. Hemoglobin is 7.2 g/dL, platelet count 42,000 per microliter, creatinine 3.1 mg/dL, and peripheral smear shows fragmented red cells. What is the underlying mechanism of his renal injury?

• A Direct invasion of tubular epithelium by enterohemorrhagic bacteria
• B ADAMTS13 deficiency permitting widespread platelet-rich microthrombi
• C Immune complex deposition in glomerular capillaries activating complement
• D Shiga toxin-mediated endothelial injury causing microvascular thrombosis ✓

Explanation

Typical diarrhea-associated hemolytic uremic syndrome follows Shiga toxin-producing Escherichia coli O157:H7. The toxin damages glomerular endothelial cells, triggering thrombotic microangiopathy with schistocytes, thrombocytopenia, and acute kidney injury. Severe ADAMTS13 deficiency causes thrombotic thrombocytopenic purpura, which features neurologic symptoms more than renal failure and lacks a prodromal bloody diarrhea.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.