Dual Energy Computed Tomography for Diagnosis and Monitoring Attempted Medical Management of a Large Urate Urolith in a Desert Tortoise (Gopherus agassizii)

Abstract

An estimated 29-year-old male, desert tortoise ( Gopherus agassizii ) under professional care presented for endoscopic liver biopsies as part of a diagnostic work-up for recurrent, profound anemia and hypoalbuminemia. Suspected cystoliths were identified during endoscopy but were not visible on contemporary radiographs. Dual-energy computed tomography (DECT) imaging confirmed the presence of a large urate urolith filling the majority of the bladder. Due to the recent clinical illness, the tortoise was considered a poor surgical candidate. Medical management consisting of urinary alkalinization with potassium citrate, vibration therapy, and daily warm water soaks was elected. Following institution of medical therapies, the tortoise began passing pieces of urate stone that were 0.25-2.0cm in diameter during daily soaks. A recheck DECT scan at two months indicated the urolith was approximately 1/3 the initial size, suggesting medical therapy was effectively treating the urolith. Unfortunately, after five months of medical therapy, the stone had increased in size again on the follow-up DECT scan. This case report suggests that medical management may be a potential option for large urate cystoliths in desert tortoises, though more research is needed to further refine effective therapeutics for such cases. The use of dual-energy CT imaging was essential in this case as it enabled confirmation of stone presence, identification of urolith composition, and monitoring of response to therapy.