Anorectal malformation (imperforate anus or ARM)

What is a anorectal malformation (imperforate anus or ARM)?

A 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, male infants are more likely to be affected.

Anorectal malformations are discovered during physical exams of the baby. Various imaging tests, including X-rays of the abdomen and spine and ultrasounds, can help the doctor understand 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.

What are the different types of a anorectal malformation (imperforate anus or ARM)?

There are several types of anorectal malformations, including:

• Narrow anal passages

• The rectum does not connect to the anus

• Imperforate anus

• Cloacal anomaly

How is a anorectal malformation (imperforate anus or ARM) diagnosed?

Some infants who have anorectal malformations have other birth defects such as congenital heart defects, spinal abnormalities or kidney and urinary tract malformations.

• Females with an imperforate anus often have an anal opening near their vaginal opening.

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 diagnosis.

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.