Anorectal Malformation | Symptoms and Causes

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What are the symptoms of an anorectal malformation?

Anorectal malformations cause abnormalities in the way a baby has a bowel movement. These problems vary depending on the type of malformation:

  • If the anal passage is narrow, your baby may have a difficult time passing a stool, causing constipation and possibly discomfort.
  • If there is a membrane over the anal opening, your baby may be unable to have a bowel movement.
  • If the rectum is not connected to the anus but there is a fistula present, stool will leave your baby's body through the fistula and enter the urinary tract instead of the anus. This can cause urinary infection.
  • If the rectum is not connected to the anus and there is not a fistula present, there is no way for the stool to leave the intestine. Then, your baby will be unable to have a bowel movement and will have a blockage of the intestine as a newborn.

What causes anorectal malformations?

As a fetus is growing in its mother's uterus, all organ systems are developing and maturing at different rates. Certain steps have to take place in the seventh to tenth weeks of gestation for the rectum and anus to separate from the urinary tract and form properly. Sometimes these steps do not occur as they should, and the rectum, anus or both may not develop normally.

Most of the time, the cause for an anorectal malformation is unknown, but in rare cases, it appears to run in families. Boys are at a slightly higher risk for this abnormality than girls.

Up to one third of babies who have genetic syndromes, chromosomal abnormalities or other congenital defects also have anorectal malformations. These genetic syndromes and other congenital problems include:

  • VACTERL association (a syndrome in which there are vertebral, anal, cardiac, tracheal, esophageal, renal and limb abnormalities)
  • digestive system abnormalities
  • urinary tract abnormalities
  • abnormalities of the spine
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