Unilateral para-ureteral cyst with ipsilateral hydroureteronephrosis in a domestic rabbit (Oryctolagus cuniculus)

Background: Ureteral cystic lesions are rarely described in pet rabbits. Case description: A two-year-old spayed female rabbit was presented for lethargy, anorexia and decreased fecal output of one-day duration. Upon physical examination, a 5-6 cm, mobile, firm abdominal mass was palpated cranially to the urinary bladder. Bloodwork was within normal limits. A contrast-enhanced abdominal computed tomography examination revealed a severe right-sided hydronephrosis, an ipsilateral hydroureter and a voluminous fluid dense nonenhancing mass abutting the right ureter. Medical management was initiated, and a laparotomy was scheduled. In surgery, the mass was diagnosed as ureteral in origin. The right kidney and ureter, along with the mass, were successfully excised and sent for histopathology and bacterial culture. A para-ureteral cyst associated with a severe unilateral hydronephrosis and moderate hydroureter were diagnosed. No associated infection was confirmed. The rabbit recovered uneventfully and bloodwork was unremarkable 2-months postsurgery. Conclusion and case relevance: This case reports an unusual and likely acquired ureteral lesion. Although rare, a para-ureteral cyst should be considered in the differential diagnosis for an abdominal mass with concurrent anorexia and decreased defecation in the female neutered rabbit.