Interesting Images111In-Labeled White Blood Cell Uptake in the Urinary Bladder in Occult Urinary Tract InfectionUllman, Henrik MD, PhD∗; Viragh, Karoly MD†; Thomas, Mariam MD†; Ni, Chiayi MD‡Author Information From the ∗Department of Radiology, Ronald Reagan UCLA Medical Center, Los Angeles †Department of Radiology ‡Department of Radiology–Nuclear Medicine Division, Olive View–UCLA Medical Center, Sylmar, CA. Received for publication August 14, 2020; revision accepted October 22, 2020. Conflicts of interest and sources of funding: none declared. Correspondence to: Chiayi Ni, MD, Department of Radiology–Nuclear Medicine Division, Olive View–UCLA Medical Center, 14445 Olive View Dr, Sylmar, CA 91342. E-mail: [email protected]. Clinical Nuclear Medicine: February 2021 - Volume 46 - Issue 2 - p 159-160 doi: 10.1097/RLU.0000000000003446 Buy Metrics Abstract 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. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.