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

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.

Cytologic and Histologic Findings of Nephroblastoma in a Captive Desert Tortoise (Gopherus agassizii)

A 97-year-old, male, captive desert tortoise ( Gopherus agassizii ) had a 2 month history of lethargy. Imaging with ultrasound, X-ray, and computed tomography revealed a 10-cm-diameter mass in the caudal coelom. Fine needle aspiration revealed spindle and epithelial cell proliferations with formation of rosettes. Exploratory surgery was performed and the mass was removed and submitted for pathology. There was no evidence of metastasis on imaging or at surgery. Histology revealed a mass arising from and compressing the kidney. The mass was composed of primitive glomeruli, tubules, blastemal cells, and mesenchymal cells, features that are diagnostic for nephroblastoma. Tubules were reactive to cytokeratin and mesenchymal cells were reactive to desmin via immunohistochemistry; other immunohistochemical markers were either negative (i.e. S-100) or non-contributory (i.e. epithelial membrane antigen, myogenin, vimentin, and Wilms’ Tumor 1). This is the first report of nephroblastoma in a chelonian.

Comment on “Individual heterozygosity predicts translocation success in threatened desert tortoises”

Scott et al. (Reports, 27 November 2020, p. 1086) suggest, on the basis of conclusions obtained from a desert tortoise reintroduction program, that higher genomic heterozygosity should be used to identify individuals for successful translocation. I contend that this recommendation is questionable given these relocated tortoises’ unknown origin, their high mortality, insufficient data on resident tortoises and other components of fitness, and potential allelic dropout.