111In-Labeled White Blood Cell Uptake in the Urinary Bladder in Occult Urinary Tract Infection

A 55-year-old woman with multiple medical problems, including anuric, dialysis-dependent, end-stage renal disease, presented with persistent fever of unknown origin. Despite extensive workup with cross-sectional imaging and panculture, the etiology was not found. Eventually, an 111In-labeled WBC scan was performed to evaluate for occult infection, which revealed intense heterogeneous uptake in the urinary bladder. Subsequent bladder catheterization showed pus and blood, which grew Klebsiella pneumoniae. The fevers resolved with adjustment of the therapy. Although urinary analysis and culture are standard practice in the workup of fever of unknown origin, anuria may obscure this common source of infection.