Genital Tract Pathology in Female Pet Guinea Pigs (Cavia porcellus): a Retrospective Study of 655 Post-mortem and 64 Biopsy Cases.

Disorders of the female genital tract are among the most common disorders in pet guinea pigs (Cavia porcellus); however, knowledge of many aspects of these disorders is sparse, especially regarding their incidence and age distribution. Ovarian cysts, as the most common genital tract disorder in guinea pigs, have been investigated in detail; however, information on the nature of these cysts is inconsistent. The present study reviewed genital tract disorders occurring within 655 full post-mortem examinations of intact female pet guinea pigs and 64 female genital tract biopsies examined over a 22.5 year period. Age distribution was determined from 550 post-mortem examinations of animals of known age. Genital tract disorders were found in 295 post-mortem examinations (45.0%) in animals with a median age of 52 months. Additionally, disorders were found in all genital tract biopsy samples from guinea pigs with a median age of 48 months. The incidence of genital tract diseases increased from 1.5% in guinea pigs ≤6 months of age to up to 77.8% in animals >6 years of age. Ovarian cysts were the most common genital tract disorder, found in 245 of the 655 post-mortem cases (37.4%) and 38 of 43 ovarian biopsy samples (88.4%). The incidence of ovarian cysts increased with advancing age, reaching 75.6% in animals >6 years. In 119 cases, histopathology and immunohistochemistry confirmed cystic rete ovarii as the only cyst type. A Fallopian tube adenoma was found in a single case, so disorders of the Fallopian tube should be considered rare. Uterine disorders were diagnosed in 17.4% of the post-mortem examinations and 98.1% of uterine biopsy samples. Uterine neoplasia, hyperplasia and inflammation were common, but occurred at different ages. The incidence of uterine neoplasia and hyperplasia was higher in older animals (>15% in guinea pigs >6 years), while the incidence of uterine inflammation was the highest (17.9%) in animals aged 7-12 months. An association between ovarian cysts and uterine neoplasia or hyperplasia was not evident. Vaginal disorders were rare and included leiomyoma, polyps and vaginitis.