Lipomas: Deadly Tumors in Horses

Anything described as “strangulating” has an ominous implication, and strangulating lipomas (also known as pedunculated lipomas) are every bit as dangerous as they sound. 

A lipoma is a fatty tumor that forms in a horse’s abdominal cavity. The tumor forms on the mesentery, a thin sheet of tissue that encloses the intestines. As the tumor grows, its increasing weight causes it to hang from the mesentery, forming a long cord-like stalk or pedicle. The tumor is then said to be “pedunculated,” and it is this stalk or pedicle that sometimes becomes looped around a section of small intestine.

The situation doesn’t always cause an immediate problem, but if the loop tightens, it prevents ingested material from passing and cuts off the blood supply to the compressed tissue. The affected horse begins to show colic signs, and discomfort may become severe.

A horse’s body condition score has little to do with the chance of having lipomas form. Fat horses might never develop lipomas, and thin horses are affected as often as their chubby pasturemates. The actual risk factors are unknown, except that the tumors become problematic only when they have developed stalks, a situation that is not frequently seen in young horses.

Diagnosis of a strangulating lipoma can be difficult, especially if some material is able to pass the constriction and discomfort alternately eases and returns. Colic caused by a strangulating lipoma will not resolve with medication, walking the horse, or any other treatment except surgical removal of the tumor. If surgery is done fairly soon in the course of the colic, prognosis is good for a full recovery. However, because lipomas seem to be most common in older equines, the horse may have other health problems that delay recovery.