Anorectal malformations (Imperforate anus) are birth defects that result in abnormal development of the anus and rectum. In these defects, the anus can be absent, narrowed, or abnormally connected to the urinary tract.
A pediatric anorectal malformation (ARM) or imperforate anus occurs when a baby’s anus and rectum do not form correctly. These malformations occur while a baby is still developing in the mother’s womb and can affect both boys and girls. However, more male infants than female infants are born with a defect in their anal opening.
The anus and rectum are critical to a child’s digestive system. In healthy children, the stool moves through the large intestine into the rectum, where it signals to the child that it’s time to have a bowel movement. The stool is then eliminated through the anus. Children with anorectal malformations have defects in the anus or rectum, preventing bowel movements from naturally occurring. They must be evaluated shortly after birth to determine what type of defect is present and if it affects the child’s ability to have a bowel movement.
These types of defects are rare, and no one understands their exact causes, though cases tend to run in families.
Doctors usually discover anorectal malformations during physical exams of the baby. Various imaging tests, including X-rays of the abdomen and spine, and ultrasounds, help the doctor get an understanding of exactly what problems exist.
These types of birth defects can be difficult to diagnose with precision, because some problems occur deep inside the pelvis, and are hard to see even with technology. Some children also have other disorders that complicate matters. These disorders can include problems in the formation of the spine, and congenital heart defects.
There are several types of anorectal malformations, including:
In general, anorectal malformations cause a child to have difficulty having a bowel movement. The specific symptoms vary by each malformation, but could include:
Some children who have anorectal malformations have other birth defects such as congenital heart defects, spinal abnormalities or kidney and urinary tract malformations. Girls with an imperforate anus often have an anal opening near their vagina.
If an infant fails to pass a stool within 48 hours of birth, has a distended abdomen or you notice a missing or malformed anus upon an infant’s initial physical examination, the infant should be evaluated immediately to determine the cause. The type and severity of anorectal malformation also determines treatment. In abnormal connections and blockages, the infant will not be able to pass stool.
Because an imperforate anus often is associated with other congenital abnormalities, a specialist in pediatric critical care should evaluate all infants with suspected anorectal malformations for possible co-morbidities such as congenital heart defects or malformations of the spine and urogenital organs.
In a fetus, certain steps have to take place in the 7th to 10th weeks of gestation for the rectum and anus to develop and separate properly from the urinary tract. Anorectal malformations occur in about 1 in 5000 live births.
Abnormal fetal development causes imperforate anus and often occurs along with other birth defects.
Repair of symptomatic anorectal malformations requires surgery. Surgeons will decide exactly which type of procedures to perform; often more than one surgery is needed to repair every existing problem completely. These surgeries take place in stages, which allows the child to heal and gain strength before the next phase of reconstruction and repair happens.
The first step for newborns who have an imperforate anus and no fistula is a colostomy. Once our experienced surgeons have created a way for the infant’s stool to collect and leave the child’s body through a temporary stoma, they will develop a more permanent plan for creating an anal opening.