Urinary bladder retroflexion secondary to pyometra in a cat

Case summary: A 9-year-old intact female domestic shorthair cat was evaluated for lethargy, vaginal discharge and intermittent perineal swelling that resolved after urination. Ultrasonography revealed severe uterine enlargement consistent with pyometra. During ovariohysterectomy, the urinary bladder was found retroflexed into the pelvic canal and manually repositioned. Despite initial improvement, perineal swelling recurred. CT confirmed persistent urinary bladder retroflexion in the absence of perineal hernia, pelvic trauma or pelvic canal mass. Exploratory celiotomy demonstrated complete absence of the ventral and left lateral vesical ligaments, providing a structural explanation for the recurrent displacement. The bladder was surgically stabilised with an incisional cystopexy, resulting in an uneventful recovery and no recurrence over 7 years. Relevance and novel information: Urinary bladder retroflexion is exceptionally rare in cats and has been described only in association with pelvic disruption or perineal hernia. This case is the first to describe bladder retroflexion in a cat independent of pelvic diaphragm failure and instead driven by severe uterine distension from pyometra. The case introduces a previously unrecognised pathophysiological mechanism in which chronic uterine enlargement exerts caudal traction on the bladder, potentially compromising vesical ligament integrity and permitting retroflexion. These findings expand current understanding of the factors influencing bladder positioning in cats and demonstrate that reproductive tract pathology alone can lead to bladder malposition. Long-term resolution after incisional cystopexy underscores the effectiveness of surgical stabilisation when bladder support structures are deficient. This case broadens the differential diagnosis for perineal swelling in female cats and highlights pyometra-induced uterine distension as an under-recognised cause of urinary bladder displacement.