What is imperforate anus?
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.
How is imperforate anus evaluated?
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.
How is imperforate anus treated?
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.
What is the long-term outlook for children after repair of imperforate anus?
The most important prognostic feature is the severity of the imperforate anus and the presence or absence of associated spinal abnormalities. Children with a low lesion, especially those who require only a perineal anoplasty, have a very good chance of having normal stool patterns. Children with spinal abnormalities of the lower sacrum and a high imperforate anus have a poorer chance of obtaining normal bowel function. Even this latter group, however, are helped by a bowel training program with diet changes and use of stimulant cathartics and regular enemas.
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This information, although based on a thorough knowledge and careful review of current medical literature, is the opinion of doctors at The University of Texas Medical School and is presented to inform you about surgical conditions. It is not meant to contradict any information you may receive from your personal physician and should not be used to make decisions about surgical treatment. If you have any questions about the information above or your child's care, please contact our doctors.