THE MERCK VETERINARY MANUAL
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Rectal Tears

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A separation, rent, or tear in the rectal or anal mucosa is seen as a result of a laceration inflicted within the lumen. Foreign bodies (eg, sharp bones, needles, and other rough material) have been implicated. Bite wounds and, in large animals, trauma from rectal palpation are common causes. The tear may involve only the superficial layers of the rectum (partial tear) or penetrate all layers (complete tear).

Constipation and reluctance to defecate are usually attributed to pain. Diagnosis is based on tenesmus and hemorrhage, perineal discoloration, and inspection of the rectum and anus; fresh blood found on a glove or on feces after rectal examination is good evidence of a rectal tear. Edema may be present when the injury has persisted. The integrity of the external anal sphincter should be evaluated carefully.

In all species, treatment should be initiated immediately. The anorectal area should be cleaned thoroughly and systemic broad-spectrum antibiotics administered. IV fluids and flunixin meglumine may be given to prevent or treat septic and endotoxic shock. In small animals, lacerations should be debrided and may be sutured through the anal orifice, via laparotomy, or through a combination of both depending on the location and degree of the tear. Antibiotics and fecal softeners should be administered postoperatively.

In cattle and horses, accidental perforation during rectal examination necessitates immediate treatment to reduce the risk of peritonitis and death. Exploration throughout the abdomen should be slow, deliberate, and smooth. The temptation to use the fingertips excessively or to push the arm through a region of resistance must be avoided. Rectal tears in horses have been classified according to the tissue layers penetrated. Grade I tears involve the mucosa or submucosa. Grade II tears involve rupture of the muscular layers only. Grade III tears involve mucosa, submucosa, and muscular layers, including tears that extend into the mesorectum. Grade IV tears involve perforation of all layers of the rectum and extension into the peritoneal cavity.

Grade I tears may be treated conservatively with broad-spectrum antibiotics and IV fluids. Flunixin meglumine may be given to prevent or treat endotoxic shock. Mineral oil is given via stomach tube to soften feces, and the diet should consist of pasture grasses or alfalfa. Grade II and III tears require immediate and more extensive surgery. A consultation with a specialist is suggested immediately after diagnosis. Grade IV tears carry a grave prognosis; they should be repaired only if small and if treatment is instituted before the peritoneal cavity is grossly contaminated.

Last full review/revision December 2013 by Stanley I. Rubin, DVM, MS, DACVIM

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