Perineal hernias result from the failure of the muscles of the pelvic diaphragm to support the rectal wall.  When these muscles fail, the rectum can dilate and abdominal organs can herniate into the area surrounding the anus.  Older male dogs that have not been neutered are at the highest risk of developing perineal hernias; females and cats rarely develop this problem.  Male sex hormones seem to influence the muscles in the pelvic diaphragm, causing them to weaken and atrophy. 

Common signs of perineal hernia include swelling around the anus, constipation, straining to defecate or pain when defecating.  If the bladder becomes entrapped, difficulty urinating may be found.  If your pet has sudden inability to urinate, you should seek immediate veterinary care.  Diagnosis of this problem is made with a rectal examination. 

Medical treatment of perineal hernias includes highly digestible diets with fiber, psyllium laxatives, stool softeners, and neutering.  Surgical treatment varies depending on the signs that are present.  Perineal hernias are repaired with a muscle flap or with a mesh material implant.  Sometimes, the colon and/or bladder need to be tacked to the body wall to keep them in place. 

Postoperatively, patients may be given a variety of medications, including laxatives, stool softeners, antibiotics and pain medications.  The surgery sites are closely monitored for signs of infection.  Complications of surgery include infection, fecal incontinence, straining to defecate, rectal prolapse, problems with urination if the bladder was entrapped, and hernia recurrence.