In rectal prolapse, one or more layers of the rectum protrude through the anus because of persistent tenesmus associated with intestinal, anorectal, or urogenital disease. Prolapse may be classified as incomplete, in which only the rectal mucosa is everted, or complete, in which all rectal layers are protruded.
Etiology of Rectal Prolapse
Rectal prolapse is common in young animals in association with severe diarrhea and tenesmus. Causative factors include the following:
severe enteritis
endoparasitism
disorders of the rectum (eg, foreign bodies, lacerations, diverticula, or sacculation)
neoplasia of the rectum or distal colon
urolithiasis
urethral obstruction
cystitis
dystocia
colitis
prostatic disease
Perineal hernia or other interruption of normal innervation of the external anal sphincter can also lead to rectal prolapse. Animals of any age, breed, or sex may be affected.
Rectal prolapse due to diarrhea or weakness of the rectal support tissue within the pelvis is probably the most common GI problem in pigs.
In cattle, rectal prolapse may be associated with coccidiosis, rabies, or vaginal or uterine prolapse; occasionally, excessive “riding” and associated traumatic injury may be causative in young bulls.
It is common in sheep with short tail docking and especially in feedlot lambs, in which high-concentrate rations may be causative.
The use of estrogens as growth promotants, or accidental exposure to estrogenic fungal toxins, may also predispose large animals to rectal prolapse.
Clinical Findings and Diagnosis of Rectal Prolapse
Cylindrical tissue mass protruding from the anus
The primary clinical sign of rectal prolapse, an elongated, cylindrical mass protruding through the anal orifice, is usually diagnostic. The mass must be differentiated from prolapsed ileocolic intussusception by passing a probe, blunt instrument, or finger between the prolapsed mass and the inner rectal wall. In rectal prolapse, the instrument cannot be inserted because of the presence of a fornix.
Other common clinical signs include ulceration, inflammation, and congestion of the rectal mucosa. Initially after prolapse, a short, nonulcerated, inflamed segment of rectal tissue is visible; later, the mucosal surface darkens, hardens, and may become necrotic.
Courtesy of Dr. Sameeh M. Abutarbush.
Treatment of Rectal Prolapse
Lavage of the protruding tissue
Reduction
Placement of a temporary purse-string suture
In all animals, identifying and eliminating the cause of rectal prolapse is of primary importance.
In small animals, treatment includes prompt replacement of viable prolapsed tissue to its proper anatomical location or amputation if the segment is necrotic. Small or incomplete prolapses can be manually reduced under anesthesia by using a finger or bougie to push the prolapsed tissue though the anal orifice. Warm saline lavage and lubrication with a water-soluble gel should be applied to the prolapsed tissue before reduction. Alternatively, hypertonic sugar solution (50% dextrose or 70% mannitol) applied topically may be used to relieve edematous mucosa.
The placement of a loose, anal purse-string suture for 5–7 days is indicated. Straining may be prevented by applying a topical anesthetic (eg, 1% dibucaine ointment) or by administering a narcotic epidural injection before or after reduction or correction.
Postoperatively, a moistened diet and a fecal softener (eg, lactulose) are recommended. Diarrhea after surgery may require treatment.
When questionable viability of tissue prohibits manual reduction, rectal resection and anastomosis are required. When rectal tissue is viable but not amenable to manual reduction, celiotomy followed by colopexy is indicated to prevent recurrence. As in medical management, epidural anesthesia may be used to decrease straining.
In large animals, caudal epidural anesthesia is suggested to decrease straining, facilitate repositioning of the prolapse, and permit surgical manipulations. Reduction and retention with a purse-string suture is recommended. The suture should be loose enough to leave a one-finger opening into the rectum in pigs and sheep, and slightly larger in cattle and horses. Rectal prolapse in mares, if neglected, can lead to prolapse of the small colon. The blood supply to the small colon is easily disrupted. Replacement of a rectal prolapse with prolapse of the small colon followed by purse-string suture of the anus has a poor prognosis.
More aggressive treatment of the prolapse is dictated by the condition of the rectum. In general, the prolapse may be salvaged by conservative measures, unless obvious deep necrosis or trauma to the tissue exists, or the everted tissue is firm, indurated, and unable to be reduced. Under these circumstances, submucosal resection or amputation should be considered.
Amputation of the rectum should be reserved for severe cases. Complete amputation has a higher incidence of rectal stricture formation, especially in swine. A prolapse ring, syringe case, or plastic tubing may be used as an alternative to surgical amputation in pigs and sheep. Postoperatively, the animal should receive antimicrobials. Fecal softeners may be used in horses. Usually, it is not economically feasible to repair rectal prolapses in lambs ready for market.
Key Points
Rectal prolapse is typically either the consequence of other diseases that result in persistent tenesmus or caused by nerve injury that results in anal sphincter incompetence.
Diagnosis of rectal prolapse is based on physical examination. Further evaluation may be needed to determine the cause.
Treatment requires either manual reduction of the prolapsed tissue or surgical resection and anastomosis.
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