Anorectal malformations are anomalies of the lower digestive tract that cause problems with how a child has a bowel movement.

What is an anorectal malformation?

Anorectal malformations are congenital (present at birth) issues that occur when the anus and rectum (the part of the large intestine just above the anus) do not develop properly. 

During a normal bowel movement, stool passes from the large intestine to the rectum and then to the anus. Muscles in the anal area help to control when a bowel movement occurs. Nerves in the area help the muscles sense the need for a bowel movement. The nerves also stimulate muscle activity.

With an anorectal malformation, several problems can occur. These include:

• The anal passage may be narrow.
• The anal opening may be covered with a tissue or membrane.
• The rectum may not connect to the anus.
• The rectum may connect to part of the urinary tract or the reproductive system. This happens through a passage called a fistula.

Causes of Anorectal Malformation

As an unborn baby is growing in its mother’s womb, or uterus, different organ systems are developing and maturing. The lower end of the intestinal tract forms fairly early in pregnancy.

In an unborn baby, the lower part of the large intestine and the urinary tract start off as one large mass of cells. Certain steps must happen in the first three months of pregnancy or gestation. These steps are needed for the rectum and anus to break away from the urinary tract and form properly. Sometimes these steps don’t happen as they should, and the rectum or anus may not develop normally. In most cases, it’s not known what causes this to happen.

Which children are at risk for an anorectal malformation?

Anorectal malformation may be seen with some genetic syndromes or congenital problems that are present at birth. These include:

• VACTERL association. This disorder includes problems with the spine, anus, heart, trachea, esophagus, kidneys, arms and legs.
• Digestive system problems
• Urinary tract problems
• Spinal problems
• Down syndrome
• Townes-Brocks syndrome. This syndrome includes problems with the anus, kidneys, ears, arms and legs.

Symptoms of Anorectal Malformation

Most anorectal malformations are found before a newborn leaves the hospital. If the problem is not found in the hospital, symptoms may include:

• Lack of stool
• Stool coming from the vagina
• Stool in the urine
• Urine coming from the anus
• Trouble having a bowel movement, or constipation

Call your child’s care team right away if an anorectal malformation was not found in the hospital but your child:

• Passes stool from the vagina
• Passes stool in the urine
• Passes urine from the anus
• Has constipation

If your child does not pass stool and is having difficulty with feeding, it is a medical emergency. You should seek medical care right away.

Anorectal Malformation Diagnosis

During the child’s regular physical exam after birth, the health care team will look at the child’s anus to see if it is open. There also may be imaging tests such as:

• Abdominal X-rays. This test makes images of internal tissues, bones and organs.
• Abdominal ultrasound. This test uses high-frequency sound waves and a computer to create images of blood vessels, tissues and organs. Ultrasounds are used to see internal organs and to check blood flow through different vessels.
• CT scan. This test uses X-rays and a computer to make images of any part of the body. This includes the bones, muscles, fat and organs. A CT scan is more detailed than an abdominal X-ray. Older children may have an abdominal X-ray.
• MRI. This test uses a magnetic field and radio waves to make detailed images of organs and structures in the body. Older children may have this test.
• Lower gastrointestinal (GI) series. This test is also called a contrast enema. It checks the rectum, the large intestine and the lower part of the small intestine. A metallic, chalky fluid called contrast is put into the rectum as an enema. It coats the inside of organs so that they will show up on an X-ray. An X-ray of the belly or abdomen shows narrowed areas called strictures, blockages and other problems.
• Upper GI series. This test is also called a contrast swallow. It checks the organs of the upper part of the digestive system. That includes the food pipe or esophagus, the stomach, and the first section of the small intestine, called the duodenum. A metallic, chalky fluid called contrast is swallowed. It coats the inside of organs so that they will show up on an X-ray. Then X-rays are taken to check the digestive organs.

Anorectal Malformation Treatment

Treatment will depend on the child’s symptoms, age and general health. It will also depend on how severe the condition is.

Most babies with an anorectal malformation will need to have surgery to correct the problem. The type and number of surgeries needed will vary, depending on the type of problem the child has. These problems may include the following:

Narrow anal passage

Surgery may not be needed for narrow anal passage. However, a procedure known as anal dilation may be done occasionally. This helps to stretch the anal muscles so stool can pass through.

Anal membrane

Surgery is done to remove the anal membrane. Anal dilations may need to be done to help with any narrowing of the anal passage.

Lack of rectal or anal connection, with or without a fistula

A series of procedures is done to repair the problem.

1. Colostomy. With a colostomy, the large intestine is divided into two sections. The ends of the intestine are brought through openings in the abdominal wall. The upper section lets stool pass through the opening (stoma) and into a collection bag. The lower section lets mucus made by the intestine pass into a collection bag. A colostomy does not damage your child’s digestion. The child can also grow before the next surgery is needed. When the next surgery is done on the lower section of the intestine, there won’t be any stool there to infect the area. The care team that works with the child’s surgeon can help you learn to take care of the colostomy. Local and national support groups may also be helpful.
2. Colostogram. The colostomy enables a procedure called a colostogram. Contrast is injected into the intestine through the lower part of the colostomy and X-rays are taken. This allows the surgeon to see whether there is a fistula (connection between the colon and urinary tract or reproductive system). This assists the surgeon with operative planning. 
3. Attaching the rectum to the anus. This surgery is often done in the first few months of life. The colostomies stay in place for a few months after this surgery. This is so the area can heal without being infected by stool. The rectum and anus are now joined, but stool will leave the body through the colostomies until they are closed with surgery. A few weeks after surgery, your child may need anal dilations to help get ready for the next phase. These dilations are something that can be done at home. 
4. Closing the colostomies. This surgery is done about 2–3 months later. The child will not be able to eat anything for a few days after surgery. This lets the intestine heal. Several days after surgery, the child will start passing stools through the rectum. At first, stools will pass often, and they will be loose. Diaper rash and skin irritation can be a problem at this stage. A few weeks after surgery, the stools happen less often and are more solid. This often causes constipation. The child’s doctor may recommend a high-fiber diet to help with constipation.

Toilet Training and Anorectal Malformation

Toilet training can begin at the usual age, between 2 and 3 years old. But a child who has had an anorectal malformation repaired may be slower than others to gain bowel control or may have long-term (chronic) constipation. This depends on the type of malformation and its repair. The health care team can explain the outlook for your child.

How can I help my child live with an anorectal malformation?

Sometimes children are able to gain good control over their bowel movements after the problem is repaired. This is often the case for children with an anal membrane or a narrow anal passage.
If your child has a more complex type of anorectal malformation, they may need to take part in a bowel management program. This can help your child control bowel movements and prevent constipation. Your child’s care team can help create a program for your child.