The rectum is the final portion of the large intestine and marks the end of the digestive tract. Feces pass through the rectum and are then excreted through the anus.

Rectal and Anorectal Narrowing (Strictures)

Rectal and anorectal strictures are narrowings of the rectum and anus due to the presence of scar tissue. The scar tissue may be caused by an injury from foreign objects or trauma (such as bite wounds or accidents) or it may be a complication of inflammatory disease.

Rectal Prolapse

Rectal prolapse is a condition in which one or more layers of the rectum protrude through the anus. A prolapse may be classified as incomplete, in which only the innermost rectal layer protrudes, or complete, in which all rectal layers protrude. The condition is common in foals in association with severe diarrhea and straining to defecate or urinate. It can be caused by intestinal, anorectal, or urinary diseases or exposure to certain fungal toxins in feed. A perineal hernia or other condition that affects the nerves of the muscle that controls the anus may also cause a prolapse.

An elongated, cylindrical mass protruding through the anus usually indicates a rectal prolapse. However, prolapses involving other parts of the intestine can look very similar. No matter what type of prolapse is present, any tissue mass protruding from the anal opening should be promptly examined by a veterinarian.

Identifying and eliminating the cause of a prolapse is a key part of treatment. For horses with rectal prolapse, epidural anesthesia (injecting anesthetic near the spinal cord) may be used to keep the horse from straining and allow the veterinarian to reposition the prolapsed tissue. Stitches will often be needed to keep the repositioned tissue in place. If neglected, rectal prolapse in mares can lead to prolapse of the small colon, a more serious condition. In some cases, surgery may be necessary to remove dead or damaged tissue or to repair the prolapse. Because of the potential complication of rectal stricture formation see Digestive Disorders of Horses: Rectal and Anorectal Narrowing (Strictures), complete amputation of the rectum is generally done only in severe cases. After surgery, antibiotics and stool softeners may be prescribed.

Rectal Tears

A tear in the rectum or anus can be caused by a sharp object that is accidentally eaten, a wound such as a bite wound, or an accidental tear during a rectal examination. The tear may involve only the surface layers of the rectum (partial tear) or penetrate all layers (complete tear). Signs may include constipation, straining or reluctance to defecate, bleeding, and discoloration of the rectum and anus. Swelling may be present when the injury has been present for more than a short time.

Treatment to avoid infection and close the wound should be started immediately. Rectal tears in horses have been classified according to the tissue layers penetrated. Grade I tears (the least serious) can sometimes be treated without surgery, using antibiotics, intravenous fluids, and stool softeners. More serious tears require immediate surgery.

Last full review/revision July 2011 by Peter D. Constable, BVSc (Hons), MS, PhD, DACVIM; Gordon J. Baker, BVSc, PhD, MRCVS, DACVS; Joseph A. DiPietro, DVM, MS; Walter Ingwersen, DVM, DVSc, DACVIM; John E. Madigan, DVM, MS; James N. Moore, DVM, PhD; Michael J. Murray, DVM, MS; Sofie Muylle, DVM, PhD; Stanley I. Rubin, DVM, MS, DACVIM; Susan D. Semrad, VMD, PhD, DACVIM; Josie L. Traub-Dargatz, DVM, MS, DACVIM