A 7 year old thoroughbred gelding with colic was anesthetized for exploratory celiotomy following episodes of chronic recurrent colic, and diagnosis of cecal obstruction on rectal exam. A complete cecal bypass via ileocolostomy was performed. Following surgery the horse developed pulmonary edema in recovery and was supported with nasal oxygen for a 24 hour period. He was intermittently colicy, depressed, and inappetant following surgery. A 3/6 systolic heart murmur at presentation progressed to a 6/6 pansystolic heart murmur with a palpable thrill several days following surgery. An echocardiogram performed by the cardiology service revealed an approximately 20 cm by 8 cm mass in his right ventricle. The most likely lesion was considered to be a large thrombus or thromboembolus.