Imperforate anus is the absence of a normal anal opening. The diagnosis is usually made shortly after birth by a routine physical examination. Imperforate anus occurs in about 1 in 5000 births and its cause is unknown.
Children who have imperforate anus may also have other congenital anomalies. The acronym VACTERL describes the associated problems that infants with imperforate anus may have: Vertebral defects, anal atresia, Cardiac anomalies, Tracheoesophageal fistula, Esophageal atresia, Renal anomalies, and Limb anomalies
The incidence of kidney and bladder problems increases with the severity of the imperforate anus, ranging from 5 to 20 percent with low lesions up to 60 to 90 percent with high lesions. While some of these anomalies may be noted on physical examination, others require further diagnostic tests.
Renal ultrasound is done shortly after birth on all infants to evaluate the kidneys. Chest X-ray, EKG, and cardiac ultrasound may be ordered to evaluate the heart. Other X-rays may be done to evaluate the trachea and esophagus and the spine.
Although the diagnosis of imperforate anus can be made by physical examination, it is often difficult to determine whether the infant has a high or low lesion. A plain radiograph of the abdomen can help locate the lesion.
Ultrasound of the perineum (rectal and vaginal areas) is also useful, with ultrasound we can determine the distance between a meconium-filled distal rectum and a finger on the perineum. We can also determine if there are any anomalies of the urinary tract or the spinal cord.
Surgical treatment of infants with imperforate anus depends upon the severity of the condition. A low imperforate anus can be repaired in the newborn period by a procedure called a perineal anoplasty. With a high imperforate anus, a colostomy (to divert the path of stool) is usually done.
The infant with a high lesion is therefore given time to grow until definitive repair can be done with a pull-through operation (in which the rectum is pulled down and sewn into a newly-made anal opening in the perineum). After surgery, the newly-formed anus needs to be dilated regularly for several months until a soft, mature scar is obtained. The colostomy can then be closed.