Protusion of viscera through the greater sciatic foramen of the pelvis is commonly known as perineal hernia or perineocele. It appears as a fluctuating mass lateral to the anus and may be either unilateral or bilateral. Although all breeds are affected, Boston Terriers, English Bull Dogs, French Bull Dogs, and Boxers are the most frequent sufferers. This condition is encountered in both sexes and is most common in older dogs.