A 68-year-old man develops livedo reticularis over both feet and a drop in creatinine from 1.4 to 3.1 mg/dL six weeks after coronary angiography. He has eosinophil count of 1,400 cells/mmL, C3 of 62 mg/dL (low), and no red cells or casts on urine microscopy. BP is 138/84 mmHg. What is the most likely diagnosis?
- A Contrast induced acute kidney injury
- B ANCA associated vasculitis
- C Atheroembolic renal disease ✓
- D Acute interstitial nephritis
Correct answer: C. Atheroembolic renal disease
Explanation
Cholesterol crystal embolisation after arterial instrumentation presents days to weeks later with livedo reticularis, peripheral eosinophilia, low complement, and a bland sediment with slowly progressive renal failure. Contrast nephropathy peaks within 24 to 72 hours and lacks cutaneous and immunological findings. ANCA vasculitis gives active urinary sediment with red cell casts rather than a bland sediment. Drug induced interstitial nephritis typically shows sterile pyuria and WBC casts, not livedo with hypocomplementaemia.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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