Hernias are defects or weaknesses in the muscles that contain the abdominal contents. Perineal hernias develop on one or both sides of the anus, due to weakness in the muscles that constitute what we call the pelvic diaphragm.

Weakness of the muscles of the pelvic diaphragm resulting in perineal hernia occurs almost exclusively in male dogs. Hormones, like testosterone, are presumed to weaken the muscles and tissues that hold the different muscles of the pelvic diaphragm. An enlarged prostate gland, common in middle-aged to older male dogs, may cause straining to urinate or defecate (bowel movement) resulting in additional stress to the pelvic diaphragm.

A perineal hernia occurs spontaneously. Occasionally, intestines or the urinary bladder can become entrapped in the hernia resulting in a potentially life-threatening emergency.

Treatment requires surgery to repair and stabilize the weakened pelvic diaphragm musculature and neutering (castration) to remove the hormonal influence testosterone has on muscle weakness and prostate enlargement.

Patients are placed on stool softeners for at least 3 weeks after surgery to decrease straining.

Complications can include infection (due to the proximity of the anus), fecal incontinence, and recurrence. In cases where the hernia is on only one side, the opposite side may also herniate in the future. The recurrence rate after surgical repair is less than 10%.

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