Anterior Displacement of the Anus

Key Features

• Common anomaly in infant girls

• In girls, diagnosis is made if the distance from the vaginal fourchette to the center of the anal opening is < 34% of the total distance from fourchette to coccyx

• In boys, the diagnosis is made if the distance from the base of the scrotum to the anal aperture is < 46% of the total distance from scrotum to coccyx

Clinical Findings

• Constipation and straining with stool is usual presentation in infants

• On physical examination, the anus looks normal but is ventrally displaced, located close to the vaginal fourchette or to the base of the scrotum

Diagnosis

• A posterior "rectal shelf" is often appreciated on internal digital examination

• In severe anterior displacement, when the anal opening is located < 10% of the distance from the vaginal fourchette to the coccyx, the anal sphincter muscle may not completely encircle the anal opening and severe obstipation similar to that seen in imperforate anus may occur

• Extreme anterior displacement of the anus may be a form of imperforate anus

Treatment

• Stool softeners or occasional glycerin suppositories usually relieve straining

• Surgery is not needed in most cases