Overview

• Eversion of one or more layers of the rectum through the anus.
• An anal prolapse (incomplete prolapse) is a protrusion of anorectal mucosa through the external anal orifice.
• A rectal prolapse (complete prolapse) is a double-layer invagination of the full thickness of the rectal tube through the anal orifice.

Signalment

• Dog and cat (especially Manx).
• Any age, sex, or breed.
• High prevalence for young, parasitized dogs or cats with diarrhea.

Signs

• Persistent tenesmus.
• Incomplete prolapse-protrusion of a portion of the circumference of the rectal mucosa that typically appears worse immediately after defecation and then subsides.
• Complete prolapse appears as a tubular hyperemic mass protruding from the anus.
• Chronic prolapses may be dark blue or black in color or the mucosa may be ulcerated.

Causes & Risk Factors

• Gastrointestinal disorders that cause diarrhea and tenesmus, such as parasitism, colitis/enteritis, constipation/obstipation, rectal foreign body, rectal deviation and diverticulum, proctitis, and rectal or anal tumors.
• Urogenital disorders, such as cystitis, urolithiasis, prostatitis, prostatic hypertrophy, and dystocia.
• Tenesmus following perineal, rectal, or urogenital surgery (e.g., perineal herniorrhaphy).

Differential Diagnosis

• Prolapsed intussusception-rule-out by passing a finger or blunt probe between the mass and the anus (the probe should not penetrate more than 1–2 cm before contacting the fornix; if the probe easily passes 5–6 cm, then suspect prolapsed intussusception) or by abdominal ultrasonography (look for increased intestinal layering).
• Neoplasia-rule-out by palpation, fine-needle aspiration and cytology, and/or biopsy and histopathology.

CBC/Biochemistry/Urinalysis

• Usually unremarkable.
• Inflammatory or stress leukogram may be present.

Other Laboratory Tests

Fecal examination may confirm parasitism.

Imaging

• Abdominal radiography and ultrasonography-usually unremarkable.
• Abdominal radiography-may demonstrate foreign body, prostatomegaly, cystic calculi, or colonic fecal distention.
• Abdominal ultrasonography-may demonstrate prostatomegaly, cystic calculi, bladder wall thickening, or intussusception.

Diagnostic Procedures

• Rectal examination to palpate for perineal hernia.
• Colonoscopy may help evaluate recurrent prolapse for an underlying cause.

Pathologic Findings

Assess viability of the prolapsed tissue by surface appearance and tissue temperature-vital tissue appears swollen and hyperemic, and red blood exudes from the cut surface; devitalized tissue appears dark purple or black, and dark cyanotic blood exudes from the cut surface; ulcerations may be present.

Drug(s) Of Choice

• Appropriate anesthetic/analgesics as needed.
• Consider epidural to facilitate surgery and reduce postoperative straining.
• Appropriate perioperative antibiotics are recommended (e.g., cefoxitin sodium 30 mg/kg IV) for resection anastomosis.
• Topical agents to aid in reduction-50% dextrose solution and KY Jelly.
• Stool softeners-docusate sodium (dogs, 50–200 mg PO q8–12h; cats, 50 mg PO q12–24h) or lactulose (10 g/15 mL solution or syrup, 1 mL/4.5 kg q8–12h to effect); continue for 2–3 weeks after removal of the purse-string suture.
• Feed a low-residue diet until purse-string suture is removed.

Contraindications/Possible Interactions

N/A

Patient Monitoring

• Purse-string suture removal in 3–7 days.
• Examine for rectal stricture if straining persists following anastomosis.

Possible Complications

• Recurrence-especially if underlying cause is not eliminated.
• Postoperative-may include infection, anastomosis dehiscence within 5–7 days postoperatively, or rectal stricture.
• Fecal incontinence after resection (sensory incontinence resulting from removal of receptors in rectal wall).

Associated Conditions

Intestinal parasitism

See Also

• Colitis and Proctitis
• Dyschezia and Hematochezia
• Intussusception

Author Eric R. Pope

Consulting Editor Stanley L. Marks