A 40-year-old male patient on maintenance hemodialysis for 2 years presented to the hospital with sudden-onset left flank pain and gross hematuria. Two years previously he had been admitted to the hospital with hypertensive emergency and acute kidney injury. A kidney biopsy at the time showed thrombotic microangiopathy. Kidney function did not improve, and hemodialysis was initiated. On the present admission his hemoglobin was 6.4 g/dL (down from 10.5 g/dL 2 weeks prior) and he received a transfusion.