Signalment:17-year-old Rocky Mountain gelding
History:There was a one month history of weight loss and one week history of lethargy, inappetence and intermittent fever. Results of a complete blood count (CBC) on the farm included a neutrophilia with toxic neutrophils, hyperfibrinogenemia and hyperalbuminemia.
Gross Lesions:A 20 cm diameter, firm, white to tan, irregularly shaped mass was found within the intercolonic fold between the right ventral and right dorsal colon, immediately proximal to the diaphragmatic flexure. On cut section, the mass contained multiple, up to 4 cm diameter, foci of a thick yellow to light green fluid (pus). A focal, transmural, mucosal ulceration was noted at the site of the mass, allowing communication between the right ventral and right dorsal colon (fistula). The regional abdominal lymph nodes were enlarged (up to 4 cm diameter) and light tan.