Ovarian Remnant Syndrome in Bitches and Queens: Clinical Aspects and Potential Neoplastic Transformations.

Ovarian remnant syndrome (ORS) is a recognized postoperative complication in spayed dogs and cats, resulting from incomplete excision or inadvertent revascularisation of ovarian tissue during gonadectomy. Affected animals typically exhibit recurrent oestrous behaviour and may develop serious sequelae, including stump pyometra, mammary neoplasia, and granulosa cell tumours. This retrospective study evaluated 93 cases (70 dogs, 23 cats) diagnosed with ORS referred to the University Veterinary Hospital of Bologna, Italy, focusing on signalment, clinical presentation, diagnostic protocols, and treatment outcomes. Diagnosis relied on a multimodal approach combining clinical history, vaginal cytology, serum progesterone assays, ultrasonography, and histopathological examination of excised tissue. Surgical excision of residual ovarian tissue was the only curative treatment, with improved outcomes when performed during hormonally active phases of the oestrous cycle to optimize remnant localisation. Histopathology confirmed ovarian tissue in the majority of cases, with neoplastic transformation identified in 10% of dogs. Bilateral ovarian remnants were more prevalent than previously reported. Surgical revision was complicated by adhesions involving vital abdominal structures, emphasizing the need for meticulous technique. These findings highlight the critical importance of precise surgical technique during initial gonadectomy, early recognition of ORS, and comprehensive surgical management to prevent severe complications and promote companion animal welfare.