A perineal hernia occurs when fat, blood vessels or organs such as the bladder have the opportunity to leave the pelvic abdominal area and enter the area along side the muscles of the the tail, gluteals and anus. The vast majority of dogs that acquire perineal hernias are older males that have not been neutered. Some breeds are more likely to acquire perineal hernias than others. A number of factors contribute to the development of perineal hernias. Genetic selection for low muscle mass in the rump area and male hormone influences are involved.
Environmental factors can play a role such as exercise and sudden impacting pressure to the abdomen.
Animals who have suffered trauma such that the intra-abdominal pressure suddenly rises can force abdominal contents through a body wall and into areas outside the abdomen. Because hernias are actually openings in body walls or barriers, the opening must be closed for a state of normalcy to exist. Sometimes a small hernia will seal itself with fat or scar tissue. These healed hernias are less strong than the original normal barrier and may reopen on occasion. Surgical correction via suturing the hernial opening is the most common method of correcting a hernia in animals.