Uterine horn aplasia with complications in two mixed-breed bitches.

Unilateral segmental uterine horn aplasia was found in 2 mixed-breed bitches. The 1st bitch was presented with clinical signs of acute abdominal pain, and pyometra was suspected. Pyometra was confirmed surgically with rupture of a blind-ending cranial portion of the anomalous right uterine horn, which had resulted in peritonitis. The 2nd bitch was presented for routine ovariohysterectomy. The right uterine horn was affected by segmental aplasia, with mucometra of the cranial portion of the affected horn. Histopathology demonstrated both uteri to have diffuse cystic endometrial hyperplasia. It is postulated that cystic endometrial hyperplasia, together with the congenital anomaly, resulted in pyometra in one case and in mucometra in the other case. This is believed to be the 1st report of uterine horn aplasia in the bitch in association with clinical signs and lesions other than infertility.