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Anorectal Malformations / Imperforate Anus

What Are Anorectal Malformations or an Imperforate Anus?

Anorectal malformations (ARMS) are also known as imperforate anus (IA). This is an "umbrella term" for a group of birth defects which affect the anorectal area.

During a normal bowel movement, solid waste passes from the colon (large intestine) to the rectum (the final section the colon) and through the anus. When a child has an ARM, the rectum and the anus do not develop properly.

Some types of ARM can cause constipation, fecal and / or urinary incontinence, infections and other problems. Some of these problems are very minor and easy to treat, with great long-term prognosis. Others are complex and affect multiple areas of life, such as sexual function and urinary and bowel control.


Anorectal malformations occur in around one in 5,000 babies. They are slightly more common in males.

The exact cause of ARMs is not known. Most babies with ARM do not have a family history of this. But the defect may be associated with a genetic cause.

Types of ARMs

Each type of ARM has unique characteristics. ARM affects each child differently. Whether a child has any problems depends a great deal on the type of ARM the child has.

Below are the most common types of ARMs in children.


ARM with recto-perineal fistula: In boys, the perineum is the small area between the scrotum and the anal sphincter. This type of ARM occurs when a baby does not have a properly formed anus and the rectum ends in the perineum.

ARM with recto-bulbar fistula: In this type of ARM, the rectum connects to the urethra at the level of the lower urethra. Urine and feces mix and empty out of the urethra (the opening where urine usually exits the body).

ARM with recto-prostatic fistula: In this type of ARM, the rectum connects to the urethra at the level of the prostate (upper urethra). Urine and feces mix and empty out of the urethra.

ARM with recto-bladder neck fistula: In this type of ARM the rectum and bladder connect in a way that is not normal. This can cause urine and feces to mix and empty out of the urethra.

ARM without fistula: In this type of ARM the rectum ends in a “blind pouch.” The rectum does not connect to anything.


ARM with recto-perineal fistula: In girls, the perineum is the small area between the anal sphincter and the labia (female external genitalia). In this type of ARM the anus does not form in the normal way and the rectum ends in the perineum.

ARM with recto-vestibular fistula: In females, there is a small area between the exterior genitals (labia) and the vaginal opening. This is called the vestibule. In this type of ARM the anus does not form in the normal way, and the rectum ends in a small opening in the vestibule. This type of ARM is often misdiagnosed as a recto-vaginal fistula.

ARM with recto-vaginal fistula: In this type of ARM there is a passageway between the rectum and vagina that is not normal. As a result, gas and feces can leak into the vagina. This is a very rare type of ARM. Patients often receive this diagnosis as a mis-label for a recto-vestibular fistula.

ARM without fistula: In this type of ARM the rectum ends in a “blind pouch.” The rectum does not connect to anything.

Cloaca: In this complex type of ARM, the rectum, vagina and urethra join into one common passageway and exit through one opening. Rather than having three passageways in the anorectal area (anus, vagina and urethra) the child has only one.

Conditions Associated with Anorectal Malformations

Approximately 50 percent of babies with anorectal malformations also have “associated defects,” sometimes described as “VACTERL association.” This condition sometimes is described as VACTERL / VATER syndrome.

VACTERL is an acronym. It stands for vertebral defects, anorectal malformation, cardiac defects, trachea-esophageal fistula, renal anomalies and limb abnormalities.

  • Vertebral defects: These affect the bones of the spinal column and can include spinal abnormalities, such as hemivertebra, absent vertebra, sacral abnormalities and / or tethered spinal cord.
  • Anorectal malformation: In girls, this can involve problems with the reproductive system that can affect the vagina, uterus and ovaries.
  • Cardiac defects: Congenital heart defects
  • Tracheal-esophageal fistula and disorders: This is a persistent connection between the trachea (the windpipe) and the esophagus (the feeding tube).
  • Renal anomalies: Kidney malformations, bladder abnormalities and dysfunction, and / or duplication of parts of the urinary tract
  • Limb abnormalities: Most commonly affecting the forearm, hand, fingers and toes

Children who have been diagnosed as having VACTERL association usually have at least three or more of these individual anomalies.

Because of these associated defects, it is important for children to receive care from a multidisciplinary team of experts that can evaluate and treat these conditions in a coordinated way.

Diagnosis of Anorectal Malformations

Anorectal malformations are most often diagnosed just after birth during the first exam. Often the doctor notices that the child’s anus is not present or is in the wrong place. Some children are diagnosed during a prenatal ultrasound. When this occurs, the doctor may refer families to a maternal-fetal medicine center such as the .

After the diagnosis, more tests are needed to understand the type of ARM a child has and what type of care is needed.

  • Abdominal X-rays provide an overview of the location of the malformation. They may help determine if the ARM is high or low in the anorectal area. These X-rays also can detect associated defects of the spine and sacrum (tailbone).
  • Renal ultrasound can show if there is something about the kidney, bladder, and urinary tract that is not normal.
  • Pelvic ultrasound is used to evaluate how the ARM may be affecting the reproductive organs in girls.
  • Spinal ultrasound can sow signs of a tethered spinal cord, where the end of the spinal cord is not attached in the normal way. A tethered spinal cord may cause neurological problems, urinary and fecal incontinence and leg weakness as the child grows. This test also is used to detect any mass in the presacral space (the area between the rectum and lowest part of the spine). Such masses most often are not malignant.
  • Magnetic resonance imaging (MRI) sometimes is needed to make a definite diagnosis of tethered cord or other spinal abnormalities. MRI also is used to view the pelvic muscles and reproductive organs.
  • Echocardiogram detects any heart defects.

Anorectal Malformation Treatment

Each child with an anorectal malformation has unique needs. The care team will create a treatment plan based on your child’s type of ARM, the presence and type of associated conditions, and overall health. Working together, these experts can help your child have the best quality of life possible.

Posterior Sagittal Anorectoplasty (PSARP)

Children who have an ARM will need a surgery called a PSARP to correct the defect. This procedure is often called an anorectoplasty. It involves moving the anus to the location within the muscles (anal sphincter) that control the bowels. This surgery allows gas and solid waste to leave the body. It may occur soon after birth or later. Timing depends on the child’s needs.

When possible, the surgeon can use laparoscopic or robot-assisted surgical techniques. This can mean less pain, less blood loss and faster healing. There is often a shorter hospital stays than for patients that have an “open” or traditional surgery.

Colostomy Surgery

Prior to the PSARP, some children have a colostomy. This surgical procedure involves creating an opening (stoma) in the abdominal wall and bringing a segment of the large intestine out through the opening. This creates a way for solid waste and gas to pass through the body until the PSARP can take place. The surgeon also creates a second opening called a mucous fistula. This helps the team perform diagnostic testing prior to the PSARP. The surgeon will close the colostomy a few months after the PSARP, since it will no longer be needed.

Post-surgery Care

When recovering from a PSARP, patients have minimal pain. The care team keeps the child comfortable, watches them closely, and looks for any signs of infection. Parents can hold and bond with their child during the hospital stay. The surgeon uses stitches that dissolve, so no procedure is needed to remove them.

After surgery, the child may have loose bowel movements often. This can cause diaper rash and irritate the skin. Within a few weeks stools happen less often and are more firm. Even after a surgical repair, some children continue to have constipation. The care team will work with you closely to minimize any symptoms. The child may need to follow a high-fiber diet and take laxatives to help address this problem. A few weeks after the PSARP, a post-op clinic visit is scheduled. At this visit, the surgeon will check progress and address any concerns.

Toilet Training

Children who have an ARM may gain bowel control more slowly than children who do not. Their type of malformation may make them not able to have good bowel control. It is important to discuss this with the care team. They can explain your child’s individual situation.

Toilet training for a child with an ARM should start at the usual age. This is often around three to four years old. If your child isn’t in normal underwear when other children his or her age are, the care team may suggest a bowel management program like the one offered through the Colorectal Center at Cincinnati Children’s. The goal of such programs is to help children achieve social continence through the use of laxatives and / or enemas and, in some cases, a special diet.

Long-Term Outlook

Children with a less complex anorectal malformation are often able to gain good control over their bowel movements after surgical repair. Those with more complex types of ARMs may need to take part in a bowel management program to prevent constipation and help them achieve social continence over their bowel movements.

Long-term follow-up care for children with an ARM may include seeing a:

  • Pediatric urologist
  • Gynecologist
  • Gastroenterologist
  • Dietitian
  • Physical therapist
  • Behavioral medicine specialist

Your child’s care team will create a treatment plan tailored to your child's individual situation. They will adjust this as your child grows.

Last Updated 09/2022

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