Urinary Cystine/creatinine Concentrations in Dogs with Suspected Androgen-dependent Cystine Urolithiasis Before and After Castration

Abstract:

Background: Castration without dietary interventions might be appropriate for dogs with suspected androgen-dependent cystinuria.Hypothesis/

Objective: Urinary cystine/creatinine (Ucys/crt) ratio will be significantly lower in dogs with cystine urolithiasis after castration and associated with the absence of ultrasonographic urolith recurrence.Animals: Intact male dogs with confirmed cystine urolithiasis

Methods: Abdominal ultrasound, urinalysis, and urine amino acid concentrations were performed at baseline (T1), one month (T2) and 3 months (T3) post castration. Genetic testing is pending. Owners were instructed to continue the dog’s normal diet. If recurrence was noted at T2, dogs were transitioned to a therapeutic diet marketed for cystine prevention.

Results: Five dogs have completed the trial: one dachshund, 2 English bulldogs, 1 French bulldog (FBD), and 1 mixed breed. At T1, all dogs had multiple uroliths removed via cystotomy and were castrated. At T2, the mixed breed and FBD had several 2-3 mm cystoliths but no clinical signs. By T3 uroliths resolved in one dog (FBD) and improved to “scant urinary debris” in the mixed breed. Overall, UCyst/crt (nMol/mg; mean  SD) decreased significantly over time: T1: 1082.2  536.9, T2: 375.9  374.9, and T3: 156.8  120.4 (p=.001). In two dogs with ultrasonographic recurrence, Ucyst/crt still decreased by 82% and 66%, respectively at T2.Clinical relevance: Ucyst/crt decreased with castration as the only intervention in 3 dogs, including the dachshund, and was associated with a lack of clinical and ultrasonographic urolithiasis. No dog required urolith removal at reevaluations. Ucyst/crt might be useful for monitoring and confirming diagnosis