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

## TL;DR

Ovarian remnant syndrome in spayed dogs and cats can lead to serious health issues and requires careful surgical removal of leftover ovarian tissue for effective treatment.

## Contribution

The study provides insights into the clinical management and surgical outcomes of ovarian remnant syndrome in dogs and cats.

## Key findings

- Surgical removal of remnant tissue during hormonally active phases yields optimal outcomes.
- Neoplastic transformation was identified in 10% of dogs with ovarian remnant syndrome.
- Bilateral ovarian remnants were more common than previously reported.

## Abstract

Ovarian remnant syndrome (ORS) is a postoperative complication occurring in dogs and cats following gonadectomy, caused by incomplete removal or accidental revascularization of ovarian tissue during sterilization. Affected animals typically present with recurrent signs of oestrus despite being previously spayed. Untreated ORS can lead to serious health issues such as stump pyometra, mammary gland tumours, and ovarian tumours, including granulosa cell tumours. This retrospective study aimed to evaluate signalment, clinical presentation, diagnostic methods, and treatment outcomes in animals diagnosed with ORS referred to the University Veterinary Hospital of Bologna, Italy. A total of 93 cases were reviewed of 70 dogs and 23 cats of various breeds and body size, with a higher incidence observed in dogs. Diagnosis was based on clinical signs and confirmed through vaginal cytology, serum progesterone assay, ultrasonography, and histopathological analysis of excised tissue. Surgical removal of the remnant tissue was the only curative treatment. Optimal outcomes were obtained when revision surgery was performed during hormonally active phases (follicular or luteal), with wide excision of the ovarian pedicle and surrounding scar tissue. These findings emphasize the importance of meticulous surgical technique and early recognition of ORS to improve long-term outcomes and animal welfare.

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.