Contents
Introduction
A congenital abnormality, whereby there is improper innervation of the large intestine, extending from the rectum, sometimes proximally into the colon.
Epidemiology
- Male predominance
Aetiology
- 30% of cases have a FH
- Several genes have been identified, one of which is on the X chromosome, and thus may explain the male predominance.
- Associated with Down’s Syndrome – 15-30% of Hirschsprung’s are in Down’s patients, and Hirschsprung’s occurs in 8% of Down’s patients
Pathology
- There is an absence of parasympathetic ganglion cells in the rectum, and sometimes also in the colon. Usually <30cm of bowel is affected.
- The parasympathetic innervation of the rectum and colon derives from the neural crest, and is usually in place by 12 weeks gestation.
- The lack of innervation results in a constantly constricted section of bowel which causes a functional obstruction when the child is born. The affected section is permanently contracted and narrowed.
- Very rarely, the small intestine may also be involved.
- In 75% of cases, only the rectosigmoid colon is involved
- In 10% of cases, the whole colon is involved
Presentation
Neonates
- Usually presents in neonatal period
- Failure to pass meconium within 48 hours of birth
- Abdominal distension
- Vomiting – may include bile staining
- Delayed passage of meconium (>24h)
- ½ of all Hirschsprung’s patients don’t pass meconium within 36h
- ½ of all children with delayed passage of meconium have Hirschsprung’s disease
- Rectal examination – often shows a narrowing of the rectosigmoid colon. When the finger is withdrawn, there may be evacuation of a watery stool. Also note that performing the rectal examination can temporarily dilate the rectum, resulting in a reduction of symptoms and a delayed diagnosis.
- Hirschsprung’s Enterocolitis – this can be life threatening. It can occur at any age although itusually presents within the first few weeks of life. There is inflammation of both the small and large intestines, and often associated C difficile infection. There may be bloody diarrhea, abdominal distension, pain, fever, foul smelling stools and vomiting. up to 30% of cases are fatal, and fatalities usually occur when the condition has not been recognized soon enough and has progressed to involve sepsis, bowel necrosis and perforation.
Infants and older children
- Chronic constipation (usually without soling), often resistant to usual treatment
- Failure to thrive
- Abdominal distension
- Early satiety
Differentials
Neonates
- Meconium ileus (cystic fibrosis)
- Pyloric Stenosis
Infants and older children
- Chronic idiopathic constipation
Investigations
- Rectal biopsy – this is the diagnostic test. Tissue is usually obtained by ‘suction biopsy’ although sometimes an anal wedge resection may be performed. The histology will shows
- Absence of ganglion cells in the myenteric plexus
- Presence of Ach positive nerve trunks
- FBC – raised WCC
- Plain AXR – may show dilated loops of bowel indicative of obstruction
- Barium enema – not particularly useful for diagnosis, but may help the estimate the length of bowel affected. Do not perform if there is any suspicion of perforation! On the scan, there affected bowel appears normal, and the dilated section is actually the normal section of bowel proximal to the affected part.
Treatment
Emergency treatment
- Intestinal obstruction :
- IV fluids
- Cessation of feeding
- NG tube and rectal exam for decompression
- Consider for surgery
- Enterocolitis
- IV fluids
- Antibioitcs
- Consider for surgery
Surgery
- This is the only effective long-term solution for treatment of Hirschsprung’s. The affected section of bowel is removed, and then the two left-over ends are anastomosed. This is the Swenson Procedure.
- If there has been obstruction/dilation of the bowel before surgery, then two procedures may need to be performed. First the affect section of bowel is removed, and a colostomy created. This allows time for the dilated section of normal bowel, proximal to the affected section of bowel to return to normal size before the second surgical procedure with the anastomosis.
- This procedure also allows time for bowel biopsies to be studied histologically to ensure all affected bowel has been removed. If any affected bowel is left in, there is a high chance the condition will recur.
- If there has been successful decompression before surgery, then the procedure may be performed in a single operation.
- After surgery there are usually no special requirements, and the complication rate is low. Most children will have normal bowel function.
- Complications:
- Soling and incontinence (<1%)
- Constipation persists (10%)
- Enterocolitis (30%)
- Risk of future adhesions / obstruction – as with any bowel surgery
- Stricture of resected segment
- Prognosis with Down’s syndrome is not good – some centres recommend permanent colostomy.
