Hirschsprung Disease

What happens in Hirschsprung disease

During early pregnancy, nerve cells migrate down the developing bowel from top to bottom. In Hirschsprung disease this migration stops early, so the last part of the bowel has no ganglion cells. Without them, that segment stays tightly contracted. Stool and gas cannot pass, and the healthy bowel above it stretches and swells (megacolon).

The length affected varies:

Symptoms

In newborns

Most cases are diagnosed in the first weeks of life:

• Delayed meconium: about 90% of healthy full-term babies pass meconium within 24 hours. Failing to pass it within 48 hours is a key warning sign.
• a swollen, tight belly
• green or brown vomiting
• poor feeding
• an explosive gush of stool and gas after a rectal exam or thermometer (the "squirt sign")

In older babies and children

Milder or shorter-segment disease may show later:

• constipation since birth that responds poorly to usual treatments
• a chronically swollen belly
• poor weight gain and growth (failure to thrive)
• tiredness and anemia
• ribbon-like or pellet stools

Unlike ordinary functional constipation, children with Hirschsprung disease rarely have stool soiling, and the rectum is usually empty on examination.

Causes and risk factors

Hirschsprung disease results from changes in genes that guide nerve cell development. The most important is RET. Several genes are involved and many cases occur without a family history.

• Sex: boys are affected about 4 times more often for short-segment disease.
• Family history: a sibling's risk is about 4%, higher with long-segment disease or an affected girl.
• Down syndrome: present in about 1 in 10 children with Hirschsprung disease.
• Other syndromes: Waardenburg syndrome, multiple endocrine neoplasia type 2 (MEN2), congenital central hypoventilation syndrome and Mowat-Wilson syndrome.

How Hirschsprung disease is diagnosed

1. Contrast enema: an X-ray after dye is passed into the rectum may show a narrow end segment and a wide bowel above it (the "transition zone"). It suggests the diagnosis but cannot confirm it.
2. Rectal suction biopsy: the definitive test. Small samples of the rectal lining are taken with a suction device, usually at the bedside without anesthesia in babies. The absence of ganglion cells, with special staining (for example calretinin), confirms the diagnosis.
3. Anorectal manometry: sometimes used in older children. It measures whether the internal anal sphincter relaxes when the rectum is stretched; it does not relax in Hirschsprung disease.
4. Abdominal X-ray: shows dilated bowel loops.

Other causes of newborn bowel blockage that doctors consider include meconium ileus (often linked to cystic fibrosis), intestinal atresia, malrotation with volvulus and anorectal malformations.

Treatment

Before surgery

The bowel is decompressed with daily rectal washouts (irrigations) using a soft tube and warm saline. Babies may receive IV fluids and antibiotics if unwell. Many babies can then be fed and have surgery within weeks. Parents are often taught to do washouts at home.

Pull-through surgery

The operation removes the aganglionic bowel and joins the healthy bowel to just above the anus, preserving the sphincter muscles. Common versions are the transanal endorectal (Soave), Swenson and Duhamel procedures. Many are now done entirely through the anus, or with keyhole (laparoscopic) assistance.

For very sick babies or long-segment disease, surgeons may first create a temporary stoma (an opening on the belly for stool), then do the pull-through months later and close the stoma.

After surgery

• Stools are frequent at first and can cause diaper rash; this settles over months.
• Regular follow-up checks bowel habits, growth and continence.
• Some children need laxatives, washouts, botulinum toxin injections into the anal sphincter, or a bowel management program.

Hirschsprung-associated enterocolitis

Enterocolitis is inflammation and infection of the bowel. It is the most serious complication and can happen before or after surgery, most often in the first 2 years. Signs are fever, a swollen belly, explosive, foul-smelling diarrhea, vomiting and lethargy. It can progress to sepsis quickly. Treatment is rectal washouts, IV fluids and antibiotics in the hospital. Parents should know these signs and seek care the same day.

Outlook

Most children have good bowel function after surgery and lead normal lives. Bowel control often improves through childhood and adolescence. Some continue to have constipation, soiling or recurrent enterocolitis, especially with long-segment disease or associated syndromes, and benefit from a structured bowel management program. Genetic counseling is offered to families, particularly when a RET variant or MEN2 is found.

Frequently asked questions

What are the first signs of Hirschsprung disease?

In newborns, the earliest sign is not passing meconium (the first dark stool) within 48 hours of birth. This is followed by a swollen belly, poor feeding and green vomiting. In milder cases, babies have severe constipation from early infancy that needs regular help to pass stool.

Can Hirschsprung disease be diagnosed in older children or adults?

Yes, though it is uncommon. Short- or ultrashort-segment disease can cause lifelong severe constipation that is diagnosed in later childhood or, rarely, adulthood. Clues are constipation since birth, a swollen belly, poor growth, and no soiling. A rectal biopsy confirms it.

Is Hirschsprung disease genetic?

It has a genetic basis. Changes in the RET gene and several others disrupt nerve cell development in the bowel. Most cases occur in families with no history, but siblings have a higher risk, and it is more common in children with Down syndrome and some other genetic syndromes.

Is Hirschsprung disease curable?

Surgery removes the affected bowel and allows most children to have normal or near-normal bowel habits. Some children have long-term constipation, soiling or episodes of enterocolitis that need ongoing care, so follow-up continues through childhood.

What is the life expectancy with Hirschsprung disease?

With diagnosis and surgery, most children have a normal life expectancy. The main risk is enterocolitis, which can be life-threatening if not treated quickly. Outcomes are less favorable for total colonic disease and when serious associated conditions are present.