Small-colon rupture attributable to granulosa cell tumor in a mare.

A large granulosa cell tumor was believed to be responsible for causing obstruction and subsequent rupture of the small colon in a 10-year-old Quarter Horse mare. Two months earlier, a mass, tentatively diagnosed as granulosa cell tumor of the left ovary, had been identified by means of rectal palpation and ultrasonography. The mare was evaluated for clinical signs of acute, severe, abdominal pain, increased heart rate, cyanotic mucous membranes, clinical dehydration, with high PCV, leukopenia, and extreme abdominal distension. A large soft tissue mass and taut band that constricted the lumen of the small colon were palpable per rectum. Septic peritonitis was diagnosed on the basis of results of abdominocentesis. Exploratory surgery revealed extensive fecal contamination of the abdominal viscera, and the mare was euthanatized because of the resultant poor prognosis. At necropsy, the small colon was occluded by a taut, left broad ligament and the ovarian mass that was proved to be a granulosa cell tumor. The occlusion had caused impaction of the small colon, with subsequent perforation at the level of the broad ligament.