A separation, rent, or tear in the rectal or anal mucosa occurs 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).
Clinical Findings and Diagnosis of Rectal Tears
Constipation and reluctance to defecate are usually attributed to pain, which can result from rectal tears. 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.
Treatment of Rectal Tears
Partial tears: medical management
Full-thickness tears: surgical repair
In small animals, partial rectal tears can typically be treated with conservative management and monitoring. Mucosal defects typically will close within 5–7 days. Systemic antimicrobial therapy is not typically indicated. Stool softeners may be indicated if there is constipation or persistent tenesmus. Complete tears 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. Antimicrobials and fecal softeners should be administered postoperatively.
In large animals, treatment should be initiated immediately. The anorectal area should be cleaned thoroughly and systemic broad-spectrum antimicrobials administered. IV fluids and flunixin meglumine may be given to prevent or treat septic and endotoxic shock.
In cattle and horses, accidental perforation during rectal examination necessitates immediate treatment to decrease the risk of peritonitis and death.
Pearls & Pitfalls
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Rectal tears in horses are classified according to the tissue layers penetrated:
Grade I tears involve the mucosa or submucosa and may be treated conservatively with broad-spectrum antimicrobials and IV fluids. Flunixin meglumine (1 mg/kg, IV, every 12 hours) 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 tears involve rupture of the muscular layers only.
Grade III tears involve mucosa, submucosa, and muscular layers, including tears that extend into the mesorectum. Both grade II and grade III tears require immediate and more extensive surgery. A consultation with a specialist is suggested immediately after diagnosis.
Grade IV tears involve perforation of all layers of the rectum and extension into the peritoneal cavity. These tears carry a grave prognosis; they should be repaired only if they are small and if treatment is instituted before the peritoneal cavity is grossly contaminated.
Key Points
Rectal tears are uncommon in dogs and cats; partial tears in dogs and cats can usually be treated conservatively.
In cattle and horses, rectal tears most commonly occur during rectal palpation and are often life-threatening.
Complete tears require surgical repair and supportive care.
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