Computed Tomographic and Ultrasonographic Features in Three Dogs with Infected Uterus Masculinus and Concurrent Genital Neoplasia

Uterus masculinus is a rare disorder of sexual development in males, characterized by the presence of tubular female genitalia. Diagnostic imaging reports of infected uterus masculinus are limited. We describe the ultrasonographic and computed tomographic findings in three dogs, all presenting with abdominal distension, pain, and systemic infection. Imaging consistently revealed a fluid-filled, bicornuate structure arising from the prostate. In two dogs, the horns extended through the inguinal rings to the scrotal testes; in the third, with a prior left orchiectomy, both horns were intra-abdominal, the right ending in a peritoneal mass. Surgery and histopathology confirmed infected uterus masculinus, with <i>Escherichia coli</i> isolated from urine in all dogs and from the structure in two. Two dogs had Leydig cell tumors, one with concurrent uterine neoplasia; the third had an ovarian or ovotesticular granulosa cell tumor. Although rare, infected uterus masculinus is potentially life-threatening and should be considered in male dogs with abdominal pain, distension, or systemic infection. This is the first case series describing combined ultrasonographic and tomographic features of infected uterus masculinus, including novel findings such as cervix-like mural narrowing and fluid-fluid levels. It is also the first imaging description of an ovarian or ovotesticular tumor in a dog with uterus masculinus.