Anorectal Malformations or Imperforate Anus

Anorectal malformations, also called imperforate anus, are a congenital defect that happens early in pregnancy, while a baby is still developing.

What to Expect

Inside the Center for Colorectal and Pelvic Reconstruction

What Is an Anorectal Malformation or Imperforate Anus? 

Anorectal malformation, also called imperforate anus, is a congenital (present at birth) defect that happens early in pregnancy while a baby is still developing.

With this defect, the baby’s anal opening (where stool exits), the rectum (the last part of the large intestine), nerves that tell the body when it’s “time to go” and muscles for squeezing (anal sphincters) do not develop properly, which can limit the child from being able to have normal, controlled bowel movements.

In a baby with anorectal malformation/imperforate anus, any of the following can happen:

  • The anal opening may be too small or in the incorrect location. This can cause painful bowel movements or severe constipation.
  • The anal opening may be missing and the colon or rectum may enter other parts of the pelvic area, like the bladder or vagina, which can lead to chronic (repeated) infections or bowel obstruction (a dangerous condition where stool becomes trapped inside the body).
  • The anal opening may be missing, and the rectum, reproductive system and urologic system form a single channel called a cloaca, through which both urine and stool pass. This can also lead to chronic infections.

What Are the Symptoms of Anorectal Malformations?

At birth, doctors check to make sure that a newborn baby’s anus is open and in the correct position. Newborns pass their first stool within 48 hours of birth, so malformations are usually detected quickly.

Meet Dr. Richard Wood, Center for Colorectal & Pelvic Reconstruction

Dr. Richard Wood serves as chief of our Center for Colorectal and Pelvic Reconstruction, one of the first centers in the world to formally integrate all specialties involved in providing complete care of the colon and rectum in kids.

Meet Dr. Richard Wood

What Are the Different Types of Anal Malformations?

Doctors typically classify malformations based on where the rectum (the lower part of the intestine) ends within the abdomen and if there is a fistula – an abnormal channel that develops between organs that can cause stool to pass through or into parts of the abdomen.

Typically, lower malformation types, which are less complex, can be repaired with one surgery and children often gain good bowel control. Children with higher malformation types, which are more complex, require more procedures, such as a colostomy at first, with reconstruction at three to six months, and will typically have more challenges gaining bowel control.

Specific Types of Malformations

Some of the malformations listed below may appear by themselves, or in combination:

Malformations found in both males and females:

  • Anorectal malformation without fistula – the anal opening is missing or in the wrong place
  • Rectal atresia and stenosis – the anus or rectum is too small to allow stool to pass
  • Rectoperineal fistula – the rectum connects to the perineum, an area of skin between the anus and genitals

Malformations found in males:

  • Rectobulbar urethral fistula and rectoprostatic urethral fistula – the rectum connects directly into the urethra (the tube that carries urine out of the body through the genitals)
  • Recto-bladder neck fistula – the rectum connects to the bottom of the bladder, where the urethra begins
  • Click here to learn more about anorectal malformations in males. 

Malformations found in females:

Kidneys and Anorectal Malformations

Patients with anorectal malformations frequently have associated urologic problems. Each patient needs a complete urologic evaluation, and any identified issues such as a single kidney, hydronephrosis, vesicoureteral reflux or neurogenic bladder need to be followed closely. If this does not occur, some children with anorectal malformations can develop permanent renal injury. Some patients have abnormal kidneys to begin with but many were initially told that they had one or two good kidneys. Unfortunately, their kidneys deteriorated over time, often silently without obvious symptoms.

There are many potential reasons for kidneys to be injured. The most common is bladder dysfunction. Other causes include infection, reflux and obstruction. Kidneys that are injured from birth or that have become injured over time may support renal function quite well until the child begins to grow. As the child grows, the metabolism of the body may overwhelm the kidneys’ ability to keep up with demand. Symptoms of renal failure or abnormal findings on simple screening blood testing may not become obvious until this time. Unfortunately, it is often too late to reverse the process and preserve good renal function when caught at this late date.

Fortunately, much of this renal injury can be prevented if the process is caught and treated early. Every patient with an anorectal malformation should know the status of their kidneys. Patients at highest risk include those with high anorectal malformations (rectobladderneck and rectoprostatic fistula, and cloacal malformations) patients who have tethered cord and patients who have urinary infection or voiding abnormalities such as incontinence or retention. Such patients should have a complete evaluation to exclude neurogenic bladder. These patients should be followed at regular intervals by ultrasound at a minimum. Other testing may be required based on the outcome of the initial complete evaluation, symptoms, and follow-up ultrasound appearance as well as often urodynamics and bloodwork (renal panel and Cystatin C). The testing required is available almost anywhere and can be accessed through most pediatricians and pediatric urologists.

How Are Anorectal Malformations Diagnosed?

If an issue is found, the doctor will do several tests to better understand the problem and to develop a long-term plan. These tests might include:

  • X-rays of the abdominal area to show how far the rectum reaches and to see if there are any problems with the way the vertebrae (backbone) and tail bone (sacrum) have developed.
  • Renal ultrasound to give the doctor a better look at the urinary tract and to see if the kidneys are blocked or if there is other abnormal fluid buildup.  
  • Spinal ultrasound or spinal MRI to look at the spine for a tethered cord, a disorder in which the spinal cord is stuck to something in the spine. This can cause neurological problems, such as incontinence (loss of bladder control) and leg weakness as the child grows. If this ultrasound shows any abnormalities, usually a spinal MRI is needed.
  • Echocardiogram to look for heart defects.

What Is the Treatment for Anorectal Malformations?

The goal of reconstructive surgery for anorectal malformation revolves around repairing or building the rectum within the sphincter muscles and pelvic floor to give a child the best possible chance at long-term continence. Prior to this surgery patients undergo a special kind of X-ray called a distal colostogram. This helps the surgeon understand where the rectum is located in the pelvis and where the fistula joins other organs or structures. This information is used to determine the best and safest way to do the reconstruction.

If the rectum is high in the pelvis above the pelvic floor or the connection is closer to the bladder neck on the urethra,  the procedure will be performed with the aid of laparoscopy (keyhole surgery), specifically laparoscopic-assisted anorectoplasty (LAARP). If the rectum is closer to the bottom, then a posterior sagittal anorectoplasty (PSARP) procedure will be done.


The surgeon makes an incision in the midline of the perineum and keeps the nerves and muscles alive by opening the structures like a book. The rectum is located and freed from its attachments. If there is a connection of fistula to the urethra or vagina, it is identified, freed and repaired. The rectum is then reconstructed within the muscles of the pelvic floor and sphincters in a way that gives the child the best possible chance at long-term continence. 


The surgeon frees the rectum through the abdomen and repairs the connection using laparoscopy. Once the rectum is freed and all connections have been repaired, the surgeon makes a small midline incision in the perineum and reconstructs the rectum in the muscles of the pelvic floor and sphincters. 

Post-operative Care

After reconstructive surgery most patients will have a foley catheter in the bladder to drain urine. This will stay in for the amount of time required for safe healing but may range from a few days to several weeks. Two to four weeks after surgery patients have an examination either in clinic or in the Operating Room to check their healing progress. Families are given the choice to perform dilations based on research done by CCPR. Each patient’s care will be discussed with the family and a care plan will be made based on the child and family’s individual needs.


What to Expect

Toilet Training

Toilet training can be started at the usual age, around 3 years old. Children who have had ARM generally gain bowel control more slowly. Depending on the type of malformation and the operation(s) done to repair it, some children have difficulty maintaining good bowel control and may need to participate in a bowel management program. Each child’s situation will be slightly different and will be determined with the help of your child’s health care team.

Long-Term Outlook

Children who had a malformation called rectoperineal fistula as well as those with rectobulbar fistula and rectovestibular fistula are usually able to gain good control over their bowel movements after surgical repair, provided they can avoid constipation.

However, those with more complex types of anorectal malformation, such as rectoprostatic fistula, recto-bladder neck fistula and cloaca may need to participate in a bowel management program to help them achieve control over their bowel movements and remain clean. Our team in the Center for Colorectal and Pelvic Reconstruction has done extensive research on bowel management. This research, combined with the results of our Bowel Management Program, have shown that the majority of patients can achieve continence and maintain these results long term.

Risk Factors

The condition affects one in 5,000 babies. It is slightly more common in males than females. No one knows why some babies are born this way, but in some cases, there is a family history. CCPR is committed to continued genomics research to help answer the unknown questions.

Why Nationwide Children's?

Nationwide Children’s care of patients with colorectal malformations stands above the rest. Here’s why: 

Lifelong Care – We are the only center in the U.S. to offer care from childhood to adulthood.

Excellent Outcomes – Our team has excellent published surgical outcomes for repairs of anorectal malformations, cloacal malformations and cloacal exstrophy. 

Multidisciplinary Team – Anorectal malformations affect children physically as well as mentally. Our expert team of surgeons, urologists, gynecologists and psychologists are ready to care for your child no matter your needs.

Leaders in Research – We are leading the way in research on anorectal malformations and other colorectal conditions. Through our research, we developed a new approach that improves continence.  

Experience – We see a high volume of patients with anorectal malformations, so are experts at diagnosing and treating children with this condition.