Anal Atresia

Anal Atresia 

Definition

The anus is either not present or it is in the wrong place.

Description

There are basically two kinds of anal atresia. In boys with high anal atresia, there may be a channel (fistula) connecting the large intestine to either the urethra (which delivers urine from the bladder) or the bladder itself. In girls, the channel may connect with the vagina. Sixty percent of children with high anal atresia have other defects, including problems with the esophagus, urinary tract, and bones. In low anal atresia, the channel may open in front of the circular mass of muscles that constrict to close the anal opening (anal sphincter) or, in boys, below the scrotum. Occasionally, the intestine ends just under the skin. It is estimated that overall abnormalities of the anus and rectum occur in about one in every 5,000 births and are slightly more common among boys. A mother who has one child with these kind of conditions has a 1% chance of having another child who suffers from this ailment.

Causes and symptoms

Anal atresia is a defect in the development of the fetus. The cause is unknown, but genetics seem to play a minor role.

Diagnosis

Usually a physician can make an obvious visual diagnosis of anal atesia right after birth. Occasionally, however, anal atresia is missed until the baby is fed and signs of intestinal obstruction appear. At the end of the first or second day, the abdomen swells and there is vomiting of fecal material. To determine the type of anal atresia and the exact position, x rays will be taken which include injecting opaque dye into the opening. Magnetic resonance imaging (MRI) or computed tomography scans (CT), as well as ultrasound, are the imaging techniques used to determine the type and size of the anal atresia. Ultrasound uses sound waves, CT scans pass x rays through the body at different angles, and an MRI uses a magnetic field and radio waves.

Treatment

Surgery is the only treatment for anal atresia. For high anal atresia, immediately after the diagnosis is made, a surgical incision is made in the large intestine to make a temporary opening (colostomy) in the abdomen where waste is excreted. Several months later, the intestine is moved into the ring of muscle (sphincter) that is part of the anus and a hole is made in the skin. The colostomy is closed several weeks later. In low anal atresia, immediately after diagnosis, a hole is made in the skin to open the area where the anus should be. If the channel is in the wrong place, the intestine is moved into the correct position sometime during the child's first year. After surgery, the pediatric surgeon uses an instrument to dilate or widen the rectum and teaches the parents how to do this daily at home to prevent scar tissue from contracting.

Prognosis

With high anal atresia, many children have problems controlling bowel function. Most also become constipated. With low anal atresia, children generally have good bowel control, but they may still become constipated.

Prevention

There is no known way to prevent anal atresia.

Key terms

Anus — The canal at the end of the large intestine through which waste is excreted to the outside of the body.

Bowel obstruction — Anything that prevents waste from moving normally to the anal opening.

Colostomy — An operation where the large intestine is diverted through an opening in the abdomen and waste is excreted.

Feces — Bodily waste material that normally passes through the anus.

Fistula — An abnormal channel that connects two organs or connects an organ to the skin.

Resources

Books

Paidas, Charles N., and Alberto Pena. "Rectum and Anus." In Surgery of Infants and Children. Philadelphia: Lippincott-Raven, 1997.

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atresia /atre·sia/ (ah-tre´zhah) congenital absence or closure of a normal body opening or tubular structure.atret´ic

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anal atresia , atresia a´ni imperforate anus.

aortic atresia  congenital absence of the aortic orifice.

biliary atresia  obliteration or hypoplasia of part of the bile ducts due to arrested fetal development, causing persistent jaundice and liver damage ranging from biliary stasis to biliary cirrhosis, with splenomegaly as portal hypertension progresses.

follicular atresia  degeneration and resorption of an ovarian follicle before it reaches maturity and ruptures.

laryngeal atresia  congenital lack of the normal opening into the larynx.

mitral atresia  congenital obliteration of the mitral orifice, often associated with hypoplastic left heart syndrome or transposition on great vessels.

prepyloric atresia  pyloric atresia; congenital membranous obstruction of the gastric outlet, with vomiting of gastric contents only.

pulmonary atresia  congenital severe narrowing or obstruction of the pulmonary orifice, with cardiomegaly, reduced pulmonary vascularity, and right ventricular atrophy. It is usually associated with tetralogy of Fallot, transposition of great vessels, or other cardiovascular anomalies.

pyloric atresia  prepyloric a.

tricuspid atresia  congenital absence of the tricuspid orifice, circulation being made possible by the presence of an atrial septal defect.

Tricuspid atresia, here displaying a ventricular septal defect and normally related great arteries, the arrows showing the altered flow of blood through the heart.

urethral atresia  congenital imperforation of the urethra.

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anal atresia

n.

Congenital absence of an anal opening due to the presence of a membranous septum or to complete absence of the anal canal. Also called imperforate anus, proctatresia.