CASE PRESENTATION An 80-year-old African American woman with a past medical history of type II diabetes mellitus, hypertension, bilateral knee replacements and peripheral vascular disease presented to the nephrology clinic for evaluation of an elevated serum creatinine. Six weeks earlier she underwent removal of a total knee prosthesis due to septic arthritis with coagulase-negative staphylococci. A vancomycin and tobramycin-impregnated cement spacer block was mixed in the operating room and implanted. Her serum creatinine concentration (sCr) was 0.9 mg/dl upon hospital discharge. Periodic laboratory studies performed at the nursing facility showed a steady increase in sCr to 1.6 mg/dl at 2 weeks and then to 3.7 mg/dl by 6 weeks (Figure 1). One week before to presentation at the nephrology clinic, she began to develop uremic symptoms including nausea, vomiting, a metallic taste, and muscle cramps. Her furosemide and lisinopril had been held for 3 weeks due to her rising serum creatinine with no improvement. Her medications on presentation were insulin, omeprazole, synthroid, metoprolol, multivitamin, clopidogrel, atorvastatin, amlodipine, warfarin and minocycline. The minocycline had been initiated after she completed a 2-week course of intravenous vancomycin. Other than the warfarin, minocycline and intravenous vancomycin, she was on no new medications. There was no documented history of hypotension and she took no non-steroidal, herbal or over-the-counter medications. Physical examination revealed that she was afebrile, her blood pressure was 124/73 mmHg and pulse was 73 beats/min. She was alert and conversant. There was pitting edema of the lower extremities to the knee, but the lungs were clear to auscultation. No rashes or joint abnormalities were noted. She did not have asterixis. She had no auditory or vestibular symptoms although these were not formally tested. Laboratory studies are shown in Table 1. Her urinalysis revealed a specific gravity of 1.013, pH of 5.0, no protein or blood, and a positive spot leukocyte esterase with 2–5 white blood count per high powered field. Urine microscopic analysis by the nephrology consult team revealed few renal tubular epithelial cells and scant granular casts without red blood cells. She remained non-oliguric during her first few days of her admission. Based upon her clinical presentation, tobramycin toxicity from her knee cement spacer was suspected. Since this diagnosis would entail surgical treatment, a transjugular renal biopsy was performed for confirmation (Figures 2, 3).
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