Rectal and Large Intestinal Atresia / Stenosis (also called anal atresia)

 

Condition Description

Rectal and large intestinal atresia or stenosis is the term used to describe a group of rare congenital conditions of the lower gastro-intestinal tract (bowel). It can range from absence of these structures to malformations of the anus and rectum (called colon, rectum or anal atresia). If these lower gastrointestinal structures are present but only partially open to the passage of stool the condition is called colon/rectum/anal stenosis. In anal stenosis the anus will look normal externally but it will not be connected to the bowel.

Another variation of the condition is called imperforate anus, where internal structures are normal but the anus is closed over with skin. Babies may have small tube-like openings (called fistulas) from the bowel that open onto the skin of the perineum or that drain into the vagina or urethra. These various abnormalities may be low (in which case the nerves and muscles will be correctly formed but skin covers the anal opening). Other times the atresia or stenosis is higher in the pelvis; if high, nerves may be malformed and muscle structures can be affected.

Imperforate anus is usually discovered during the baby's newborn examination. The baby will have an unusual appearing anus coupled with abdominal distention, as the baby is unable to pass meconium (the first stool after birth, dark and sticky in consistency). Anal stenosis may not be immediately discovered but symptoms such as abdominal distention and poor feeding will be noticed soon after birth.

During early fetal life the bowel and surrounding structures may fail to develop, perhaps due to lack of blood supply to that area of the body. These conditions are sometimes detected before birth because of polyhydramnios (excess amniotic fluid). The cause is unknown. In some families there is a hereditary pattern of several members having the condition, but this is not often the case. Maternal diabetes as well as prenatal alcohol use may be related to this disorder.

Prevalence

Anal atresia or stenosis occurs in about 3 of 10,000 live births, with slightly more males affected. Imperforate anus occurs in 1 of 5000 live births.

Common Associated Conditions

Anal atresia or stenosis is often associated with other birth defects, particularly chromosomal abnormalities such as Trisomy 21 (Down syndrome). It is seen more often in babies born prematurely, particularly with babies who have intrauterine growth retardation (slow growth during fetal life). There is an increased risk of anal atresia conditions in multiple gestation pregnancies (twins, triplets, etc). Cardiac anomalies are seen in 25% of children with imperforate anus. Tracheoesophageal fistula, esophageal atresia and limb abnormalities are also associated with anal stenosis/atresia, as well as defects in the spinal vertebrae. Kidney and bladder problems occur in 5-20% of children with low defects and 60-90% with high defects.

Short-Term Treatment and Outcomes

Renal ultrasounds and various x-rays, electrocardiograms (EKGs) and cardiac ultrasounds will be done to see if the baby has other related conditions. Immediate surgery is necessary to create a passageway for stool drainage, either by opening the anus (called a perineal anoplasty), or by creating a loop of bowel that opens onto the abdomen (a temporary colostomy). At some point when the baby is stable and growing well the lower bowel will be reconstructed and fistulas will be repaired. The type of surgery will depend on the nature of the defect. A pull-through surgical procedure of the bowel and colostomy closure will be done several months later after the anus and bowel heals. Children may need regular visits to the hospital for dilatation of the repaired anus and rectum to prevent it becoming too tight (called a stricture or stenosis).

Long-term Treatment and Outcomes

The major long-term concern is being able to locate and repair the nerve and muscle structures around the rectum and anus so that the child will be able to have normal bowel control and function. Because the urethra is so close to those structures there is also a concern about affecting the child's urinary function and control. The severity of the bowel defects and the presence of any other associated defects (i.e. spinal abnormalities, etc) determine how well the child will do after this surgery.

Most anorectal malformations can be corrected very successfully with surgery, and normal bowel function can be established. Children will need a special high-fiber diet and stool softening medications throughout childhood. Enemas may also be needed in order to establish a regular bowel pattern. Ongoing care from a gastroenterologist is typically necessary.

Common Complications

Complications would include surgical infections, paralysis of the bowel after surgery (temporary; called paralytic ileus), persistence of rectal fissures, leakage of stool (called fecal incontinence), and difficulties in establishing normal bowel function.

Implications for Children's Development

These lower bowel conditions can affect children's development in many ways if they are associated with other severe abnormalities of the heart, esophagus, kidneys or spine. In many children, however, the rectal/anal surgery will take place soon after birth and the children will have an excellent outcome with no further problems. They will grow well if they can be well nourished, and their intellectual development should not be hampered.

Other children who have these bowel abnormalities as well as other significant congenital defects will have significant developmental delays and a variety of health concerns requiring ongoing medical care.

Fecal incontinence can be very difficult for children's social development and self-esteem if it persists into school age. A school nurse can be very helpful to the child and family in finding ways to allow the child to go to the bathroom as needed and to have the privacy for self-care. The child and family will need support and education as they develop a bowel-training program. The best combination is a high fiber diet coupled with regular times of sitting on the toilet each day.

For more information, including resources for parents and general information about imperforate anus and rectal atresia conditions, visit the following websites: