anal atresia

Also found in: Dictionary, Thesaurus, Encyclopedia.

Anal Atresia



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


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.


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.


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.


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.


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.



Paidas, Charles N., and Alberto Pena. "Rectum and Anus." In Surgery of Infants and Children. Philadelphia: Lippincott-Raven, 1997.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


congenital absence or closure of a normal body opening or tubular structure; see also obstruction. adj., adj atret´ic.
anal atresia (atresia a´ni) imperforate anus.
aortic atresia
1. congenital absence of the aortic orifice.
2. absence or closure of the aortic orifice, a rare congenital anomaly in which the left ventricle is hypoplastic, so that oxygenated blood passes from the left into the right atrium through a septal defect, and the mixed venous and arterial blood passes from the pulmonary artery to the aorta by way of a patent ductus arteriosus.
aural atresia absence of closure of the auditory canal.
biliary atresia congenital obliteration or hypoplasia of one or more components of the bile ducts, resulting in persistent jaundice and liver damage.
choanal atresia blockage of the posterior nares. When the blockage is bilateral in a newborn, it produces acute respiratory distress because neonates are nose-breathers. Diagnosis is confirmed if a catheter cannot be passed through the nares. Until surgery is done to relieve the obstruction, insertion of an airway may be necessary.
esophageal atresia congenital lack of continuity of the esophagus, commonly accompanied by tracheoesophageal fistula, and characterized by accumulations of mucus in the nasopharynx, gagging, vomiting when fed, cyanosis, and dyspnea. Treatment should begin with suction of the upper esophageal pouch, followed by surgical repair by esophageal anastomosis and division of the fistula as soon as the infant's general condition permits.
follicular atresia (atresia folli´culi) the normal death of the ovarian follicle when unfertilized.
laryngeal atresia congenital lack of the normal opening into the larynx.
mitral atresia congenital obliteration of the mitral orifice; it is associated with hypoplastic left heart syndrome and transposition of great vessels.
prepyloric atresia congenital membranous obstruction of the gastric outlet, characterized by vomiting of gastric contents only. Called also pyloric atresia.
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 atresia.
tricuspid atresia absence of the tricuspid orifice, circulation being made possible by 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. From Dorland's, 2000.
urethral atresia imperforation of the urethra.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

a·nal a·tre·si·a

, atresia ani
congenital absence of an anal opening due to the persistence of epithelial plug (persistence of the anal membrane) or to complete absence of the anal canal.
Farlex Partner Medical Dictionary © Farlex 2012

a·nal a·tre·si·a

, atresia ani (ā'năl ă-trē'zē-ă, ă-trē'zē-ă' ā'nī)
Congenital absence of an anal opening due to the presence of a membranous septum (persistence of the cloacal membrane) or a complete absence of the anal canal.
Synonym(s): imperforate anus (1) , proctatresia.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

anal atresia

A congenital condition in which the anus is imperforate. There is often an associated ANAL FISTULA.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
Vertebral defects, Anal atresia, T-E fistula with esophageal atresia, Radial and Renal dysplasia: A spectrum of associated defects.
An approach to the identification of anomalies and etiologies in neonates with identified or suspected VACTERL (vertebral defects, anal atresia, tracheoesophageal fistula with esophageal atresia, cardiac anomalies, renal anomalies, and limb anomalies) association.
For example, the baseline prevalences of anal atresia and right ventricular outflow tract obstruction defects are each estimated to be about 5.5 cases per 10,000 live births; thus, even if a specific SSRI increased rates by a factor of four, the risk of having an affected child would still be only 0.2%," they noted.
Infant had a single lower limb (Fig.1), anal atresia and single umbilical artery.
Anomalies associated with urachal remnants such as vesicoureteral reflux, meatal stenosis, hypospadias, umbilical and inguinal hernias, cryptorchidism, anal atresia, omphalocele and crossed renal ectopia are rare, but should also be considered.
Patients often exhibit congenital anomalies that include limb defects; reduction deformity of the arms and forearms; no digits or missing digits on the hands; reduction deformity of the legs; hind legs; no digits or missing digits on the feet; spinal dysraphism; congenital diaphragmatic hernia; lung hypoplasia or lung agenesis; thoracopagus; micrognathia; microgastria; craniostenostosis; anal atresia or anal stenosis; hypoplasia; and, polysplenia.
The major anomalies included pyloric stenosis, anal atresia, hypospadias, cleft palate, talipes, and dislocated hips.
The association among coloboma iridis, auricular deformity, and anal atresia was first described by Haab in 1879.