Case Report: Computed tomographic diagnosis of asymmetric bilateral uterine horn torsion secondary to benign uterine leiomyomas in a non-gravid dog.

Uterine torsion is uncommon in dogs and most commonly involves a single uterine horn. An 11-year-old intact female Pomeranian was presented with a 2- to 3-day history of abdominal distension, dyspnea, anorexia, vomiting, and oliguria. Clinicopathologic findings indicated renal compromise, electrolyte abnormalities, tissue injury, and marked systemic inflammation. Radiography and ultrasonography revealed large bilateral abdominal masses with peritoneal effusion, although the organ of origin could not be determined. Contrast-enhanced computed tomography (CT) demonstrated masses arising from both uterine horns, with absent central enhancement on the right, minimal central enhancement on the left, and thin peripheral rim enhancement of both masses, suggesting vascular compromise and ischemic injury. Both ovaries showed preserved contrast enhancement, and spiral twisting of both uterine horns and bilateral whirl signs were identified, with the changes being markedly more pronounced on the right. These findings permitted a preoperative diagnosis of asymmetric bilateral uterine horn torsion. Exploratory laparotomy confirmed approximately 1,080° rotation of the right horn around the left horn and 270° rotation of the left horn around its own axis, without gross rupture of the broad ligament. En bloc ovariohysterectomy without prior detorsion and excision of the vaginal mass were performed. Histopathologic examination confirmed leiomyomas of both uterine horns and of the vaginal mass, with extensive hemorrhage and necrosis of the right horn. The dog recovered uneventfully and remained clinically well 9 months after surgery. To the authors' knowledge, this is the first report of bilateral uterine torsion associated with benign leiomyomas in a dog and the first description of bilateral whirl signs on CT in canine uterine torsion.