About 1 in 5,000 babies are born with a rare but treatable disorder of the bowel known as Hirschsprung's disease.
Normally the muscular walls of the bowel continuously squeeze and relax to push stools along, a process controlled by your nervous system.
In Hirschsprung's disease, a section of the bowel is permanently squeezed in and narrowed, and is unable to relax. Stools become stuck in that section of the bowel, building up to form a blockage.
The faulty section is usually right at the end of the bowel, affecting the last segment of the large bowel (sigmoid colon) and the rectum (where stools are held before you go to the toilet).
Hirschsprung's disease is usually diagnosed after birth and treated with surgery straight away.
What are the signs of Hirschsprung's disease?
One of the main warning signs in a newborn baby is failing to pass meconium.
Meconium is the dark, tarry stool that healthy babies pass within the first 48 hours of being born. Many babies with Hirschsprung's disease cannot pass meconium until many days later.
Other warning signs in a newborn baby are:
swollen belly and constipation
vomiting a green fluid (bile)
Signs in older infants and children are:
swollen belly and complaining of tummy ache
ongoing constipation that doesn't get better with the usual treatments
feeling full quickly, so not feeding well or gaining much weight
How is it diagnosed?
The signs are usually spotted and investigated soon after birth. Even if it is missed at birth, most cases will be diagnosed while the child is still a baby.
The first investigation is an X-ray. If this shows a blockage and bulge in the bowel, Hirschsprung's disease should be suspected.
This diagnosis can be confirmed by doing a rectal biopsy, which involves inserting a small instrument into the baby's bottom and removing a small sample of the affected bowel. This is then examined under the microscope to see if the nerve cells are missing.
What's the cause?
The muscles of the bowel are controlled by nerve cells called ganglion cells in the bowel wall. They stimulate the muscles to contract (squeeze in) and relax.
In Hirschsprung's disease, these ganglion cells are missing from the affected section of bowel. For some reason, they did not develop in that area when the baby was growing in the womb.
A number of genes have been identified that can cause this, which explains why the disease sometimes runs in families.
The exact cause is not clear, but Hirschsprung's disease is not caused by anything the mother did while she was pregnant.
Hirschsprung's disease is four times more common in baby boys than girls. Some will also have another inherited condition, such as congenital heart disease or Down's syndrome.
How is it treated?
All children with Hirschsprung's disease will need surgery.
As they wait for surgery, they will probably need regular bowel washouts, where a thin tube is inserted into their bottom and warm salt water is then used to soften and flush out the trapped stools.
Most children will be well enough to have the standard "pull-through" operation, where the affected section of bowel is removed and the healthy section of bowel is connected directly to the anus (the opening at your child's bottom).
If your child isn't well enough to have this major surgery, they will have it in two stages.
The small intestine is first detached from their large bowel and re-routed through an opening in their tummy called a stoma. This procedure is known as an ileostomy. If the large bowel is diverted, the procedure is called a colostomy.
Stools pass directly out of this opening and into a pouch worn on your child's body. It allows their affected section of bowel to recover before they have the main procedure, where the bowel is reconnected inside.
The main operation can either be done using:
laparoscopic (keyhole) surgery, which involves inserting surgical instruments through tiny cuts
open surgery, where a larger cut is made in your child's belly
Speak to your surgeon about which is the best option for your child.
Risks of surgery
No surgery is risk-free. There's a small chance of:
bleeding during or after the operation
the bowel contents leaking out inside your child's body, which could lead to serious infection (peritonitis) if stools are not immediately redirected through a stoma
narrowing (stricture) of the new bowel connection
Recovery from surgery
Your child will need pain-relieving medicine through a drip for the first few days, which they can later take as swallowable medicine.
They'll also be on a drip of fluids for the first few days while their bowel recovers and until they can manage food.
No special diet is needed, but it's important they drink plenty of fluids as they recover at home.
After surgery, your child should recover well and their digestive tract should function normally.
They'll probably have a sore bottom for a while whenever they pass stools. You can use baby oil to gently clean their bottom and nappy cream after each change to help. Leave your child's bottom open to the air whenever possible.
Will my child have any further problems?
After surgery, most children are able to pass stools normally and have a normal functioning digestive tract. They may take a bit longer to toilet train, however.
Some may remain constipated and need to follow a high-fibre diet and take laxatives. Your doctor will advise about this treatment.
One possible complication is leaking stools (bowel incontinence), which can continue throughout the teenage years and be very distressing.
If you need support for this, read our advice about soiling in children, speak to your GP or see the External links.
If your child develops a swollen belly again, with or without foul-smelling diarrhoea, call your doctor immediately.
They may have a serious bowel infection called enterocolitis, which will need urgent treatment with antibiotics. Other possible signs of enterocolitis are bleeding from the bottom, fever and vomiting.
It's also possible – although uncommon – for the section of bowel to become narrowed or blocked again, requiring further surgery.
Coloured barium X-ray of the abdomen of a child with Hirschsprung's disease, showing a swollen large bowel.