Hirschsprung's disease (congenital megacolon, aganglionic megacolon) is characterized by an absence of ganglion cells in the colon resulting in a functional obstruction. It is named after the Danish physician Harold Hirschsprung.
Most of the times the disease is diagnosed shortly after birth but in some patients it may be diagnosed later in childhood. The most common presenting features in infants include the following .
The clinical features in older children are:
The general physical examination of a child with Hirschsprung’s disease will show distended abdomen. Loops of bowel may be felt in the abdomen. There will be loss of muscle tone in the rectal muscles on rectal examination.
The investigations carried out to confirm the diagnosis include:
The management of patients with Hirschsprung’s disease consists of supportive care and definitive treatment. Supportive or medical treatment is to treat general manifestations of the disease before definitive surgical treatment is performed and also to manage postoperative bowel function. It consists of:
Post operatively, antibiotics are given to prevent enterocolitis. If enterocolitis develops, then resuscitation along with antibiotics and mast cell stabilizer drugs are helpful. Injection of botulinum toxin within the contracted internal sphincter may help in inducing normal bowel movements in postoperative patients.
The definitive treatment for Hirschsprung’s disease is surgery. The affected part of the colon is resected and an end to end anastomosis is made between the normal bowel loops. There are a number of procedures to repair the aganglionic colon.
Mortality rates in untreated Hirschsprung’s disease are approximately 80%. The prognosis of Hirschsprung’s disease is generally good after surgery. Some of the patients may develop complications like constipation, fecal incontinence or enterocolitis which may lead to mortality rates as high as 30%. Patients who suffer from an associated syndrome or have long-segment disease have a much poorer prognosis  .
Hirschsprung’s disease is known to be caused by mutations in the RET-proto oncogene on chromosome 10q11.2. Family history of the disease is positive in about 30% of cases. In addition, there are several syndromes associated with the occurrence of Hirschsprung’s disease - the most common of which is Down syndrome. Other less common syndromes are Waardenburg-Shah syndrome, Goldburg-Shpritzen megacolon syndrome and congenital central hypoventilation syndrome.
Hirschsprung’s disease is a congenital disorder that may be familial or acquired. The condition is more common among white males. The male to female ratio is 4.32:1. The disease affects 1 in 5400 to 7200 newborns in the United States annually. It is more common in Asian-Americans. According to international data, the annual incidence rate of the disease is estimated to be 1 case in around 1500 to 7000 newborns  . The condition is found to be present in about 9% of patients with Down syndrome .
The enteric nervous system supplying the intestines consists of submucosal (Meissner’s) plexus, myenteric (Auerbach’s) plexus and the smaller mucosal plexus. The absorption, secretion, motility and blood flow of the gut is under the control of enteric nervous system. The normal intestinal motility is under the control of the enteric ganglia. The intrinsic neurons cause relaxation of the intestinal smooth muscles while extrinsic neurons containing cholinergic and adrenergic fibers cause contraction and inhibition respectively.
In Hirschsprung’s disease, the myenteric and submucosal plexuses are absent and the control of intestinal smooth muscles is predominantly extrinsic. This leads to increased smooth muscle tone in the intestine which in turn causes uncoordinated peristalsis and functional obstruction.
The ganglions in the enteric nervous system are derived from the neural crest cells which migrate to the intestine during the twelfth week of development. One of the most accepted causes of aganglionosis in Hirschsprung’s disease is the failure of migration of the neural crest cells. In other cases, there might be apoptosis, failure of proliferation or improper differentiation of the neuroblasts despite their normal migration to the colon. Alternatively, there may be some dysfunction or absence of the factors like laminin, fibronectin, neural cell adhesion molecule and neurotropic factors, which are responsible for normal enteric ganglion development.
Genetic studies suggest that the most common gene mutation associated with Hirschsprung’s disease is the RET proto-oncogene  . Overexpression of DVL1 and DVL3 gene has also been found to be present in Hirschsprung’s disease. In addition to mutation in the RET proto-oncogene, about 50% of the patients with this disorder have got mutations in several other genes; GDNF, GFR alpha1, NRTN, EDNRB, ET3, ZFHX1B, PHOX2b, SOX10 and SHH .
There is no preventive measure against Hirschsprung disease as it is a developmental disorder.
Hirschsprung’s disease, also known as congenital aganglionic megacolon, is a developmental disorder characterized by inability of the distal colon to relax due to the failure of migration of neural crest cells into the colon to form the enteric nerve plexuses. There is absence of ganglion cells in the affected segment due to which the affected part of the colon remains contracted and the proximal segment becomes dilated. This results in functional intestinal obstruction.
About 90% of the patients are diagnosed in the new born period. Hirschsprung’s disease is suspected in any neonate who does not pass meconium within 24 to 48 hours of birth. The condition is diagnosed with barium enema and rectal biopsy and is treated by surgically removing the affected portion of intestine.
Hirschsprung’s disease is a congenital anomaly of the colon in which the normal peristaltic movements in a portion of gut are absent leading to functional obstruction of the intestine. The infants with this disease are unable to pass meconium after birth. Some patients may present in childhood with symptoms of chronic constipation, distended abdomen and malnutrition etc. if diagnosed timely, it is not a life threatening condition and is treated successfully by surgery.