University Hospital Southampton NHS Foundation Trust

Anorectal malformations

Anorectal malformation is a term used to describe several types of anomalies. The anus (which is the opening in your bottom through which stool passes through) and the rectum (which is the part of bowel immediately above the anus) have not developed properly. Your baby may be born with:

  • No anal (bottom) opening at all
  • An ectopic anus (small opening in the wrong place)
  • Anal stenosis (narrowed opening of the bottom)

We usually classify them as “high” or “low” anomalies depending on the gap between the bowel and the skin. The bowel may be joined by a fistula (communicating tube) to another structure such as the urinary tract or the reproductive system. The surgeon responsible for co-ordinating your baby’s care will explain in detail the type of anomaly we believe your baby has.

If your baby cannot pass meconium (baby poo) properly then their bowel is obstructed. This, if not treated, puts them at risk of infection and possible perforation of the bowel. Your baby may also have a fistula connecting to their urinary system which could put them at risk from an urinary tract infection.

Why does it occur?

We are unclear as to why it occurs but we do know that sometimes the process of development in the womb is not complete. This is not due to anything that you have done or not done during your pregnancy. It is a rare problem that affects slightly more boys than girls (around 1 in 5000 babies).

Will my baby have any other problems?

Most babies will have otherwise of developed normally. However there can be other problems with the development of other systems such as the kidneys, heart, spine and oesophagus (VATER syndrome). Other tests such as x-rays and ultrasound scans will be done in the first few days to exclude these.

How are anorectal malformations diagnosed?

It is usually obvious following delivery that the anus is not present or in the wrong place. Sometimes the problem is not immediately apparent and the baby is fed as usual. If this is the case your baby may vomit and the abdomen (tummy) may become progressively distended (bigger).

If the anus is stenosed there may be a delay in passing meconium that happens normally within the first 24 hours following delivery. If there is a fistula present, meconium may be present in the urine or, in girls, come out through the vagina.

What is the treatment?

Feeds, if started, will be stopped and a nasogastric tube (a tube through the nose down to the stomach) will be passed. This enables us to keep the stomach empty so the baby does not vomit and your baby will be given fluid through a drip sited in one of its veins. An X-ray will be taken after 24 hours of age (this allows time for swallowed air to travel through the bowel) to determine whether the anomaly is:

  • 'Low' - if the bowel is present just under the skin
  • 'High' - if the bowel ends up higher within the baby’s tummy

Treatment will vary depending on the classification but usually an operation will be necessary. All babies will need a small dose of antibiotics to prevent urine infections because of the possibility of a fistula or an associated problem in the urinary tract. This will need to continue for at least several months.

Treatment of a low anomaly

An operation, called an anoplasty, will be performed that will expose the anus under the skin. This is a relatively minor operation and your baby should be able to feed and pass stool within a day or so of the operation.

A few days later it will be necessary to start passing a dilator (small plastic rod) on a daily basis into the new opening to prevent it narrowing. On the first occasion this may need to be done under an anaesthetic. Subsequently you will be shown how to do this and supported until you feel competent to do this independently.

What are the short/long term effects of a low anomaly?

The main short term problem is a narrowing of the bottom as discussed above. This should be preventable by passing the dilator daily for the first few months of life.

In the longer term constipation may be a problem but this can usually be managed by diet or medication.

Treatment of a high anomaly

Your baby will require a temporary colostomy initially. This means bringing an end of the bowel out on to the surface of the tummy so the baby will pass stool into a bag rather than through the anus.

Your baby will start feeding a couple of days after surgery and we will teach and support you in caring for the colostomy. When you are ready, you will all be able to go home, this is normally about one week later.

Your baby will have the colostomy for several weeks/months until a more complicated operation is performed to create a new bottom for your baby. Before this operation your baby will have more investigations get more detail of the anatomy of the bowel.

What are the short/long term affects of a high anomaly?

Sometimes the colostomy may recede or prolapse but this does not normally require further treatment. Following corrective surgery you will be taught how to pass a dilator (see under low anomalies) to prevent narrowing occurring,

Most children are unable to develop normal bowel control but there are ways that we can help to achieve this through a bowel management program. With modern techniques it is usually possible for children to be clean most of the time. This will be discussed further throughout long-term outpatient follow up.

Parent to parent link

Many parents who have experienced this condition with their baby have indicated that they would be willing to speak to other parents. If you would like to make use of this service please contact us to find out more or speak to the team caring for your baby.

Internet links

Please see the box on the right at the toip of this page for other internet sites providing information on this condition.


University Hospital Southampton NHS Foundation Trust produce guidelines as an aid to good clinical practice. They represent recognised methods and techniques of clinical practice, based on published evidence. The ultimate judgement regarding a particular clinical procedure or treatment must be made by the clinician in the light of the clinical data presented by the patient and the diagnostic or treatment options available. The guidelines issued are not intended to be prescriptive directions defining a single course of management and departure from the local guidelines should be fully documented in the patient's case notes at the time the relevant decision is taken.