One of the most common surgical emergencies in the newborn is for bowel obstruction. When a newborn develops abdominal distention and fails to pass his first stool, distal bowel obstruction must be suspected. There are several different etiologies for distal bowel obstruction, and amongst the list of differentials is Hirshsprungâ€™s disease.
Hirshsprungâ€™s disease is a motor disorder of the colon, which results in a functional (or pseudo-) obstruction. It occurs in about 1 in 5000 live births. In the majority of patients (75-80%), only the rectosigmoid colon is affected; however, in 10% of patients, the entire colon is involved. Males are affected three to four times more than females, except in cases where the entire colon is involved, in which case the male:female ratio is 1:1.
During development, the normal colon is innervated by derivatives of the neural crest cells (ganglionic cells) as it grows in length. These cells are responsible for relaxing the colon during peristalsis. Hirshsprungâ€™s disease results from failure of the neural crest cells to migrate to the colon, which in turn results in aganglionic bowel. This portion of the bowel does not relax with peristalsis. This gives rise to the predominant symptoms of abdominal distention and failure to pass meconium in the first 24-48 hours of life. If the diagnosis is unrecognized early on, the infant may present with enterocolitis of Hirschsprungâ€™s disease, also known as toxic megacolon. These patients are typically critically ill with the signs and symptoms of fever, sepsis, diarrhea, and abdominal distention. Those born with mild disease may not present with signs of Hirschsprungâ€™s disease until later in childhood/young adulthood. These patients will have a history of chronic constipation and malnutrition secondary to malabsorption and protein-losing enteropathy.
Hirshsprungâ€™s disease has been linked to about eight genetic mutations, with the RET proto-oncogene being the predominant mutation. It is associated with certain syndromes, such as MEN 2, Waardenburg syndrome, and cardiac disease. Among chromosomal abnormalities, Downâ€™s syndrome is the one most commonly associated with Hirshsprungâ€™s disease. Three percent of those with Hirschsprungâ€™s disease also have Downâ€™s syndrome.
When Hirschsprungâ€™s disease is suspected, plain films of the abdomen are initially ordered. These films typically reveal decreased air in the rectum and a dilated colon filled with stool. Barium or water-soluble contrast agents (Gastrografin) can be used as well. These agents are utilized to view the transition zone, which highly suggests Hirschsprungâ€™s disease (97% specificity, 76% sensitivity). The transition zone is best visualized with the child in the lateral position. It reveals a transition between the aganglionic, distal, stool-free segment and the dilated, proximal, stool-filled segment of innervated bowel. This zone is most frequently visualized in older children, but with good technique (constant filming and monitoring of the laterally positioned child), it may be seen in neonates. Anorectal manometry may aid in diagnosis, but its results are less accurate in neonates. Definitive diagnosis is made via suction biopsy of the rectal mucosa in infants. Full-thickness biopsy is recommended in older children. This procedure is the most sensitive (93%) and specific (100%) of all tests. Diagnosis is made by the finding of absence of ganglion cells.
Initial treatment for Hirshsprungâ€™s disease differs depending on the condition of the child. If a child is very ill, an ileostomy or colostomy is often performed initially in order to decompress the dilated bowel. Once the child is stable, they undergo pull-through surgery, which is the definitive treatment. There are several different pull-through surgeries; however, all involve removal of or bypassing the dysfunctional bowel and reconnecting the functional bowel to the rectum.
In the early post-operative months, the child may experience diarrhea and incontinence secondary to loss of the absorptive surface of the colon and dysfunction of the anal sphincter. These conditions tend to improve as the child ages. The great majority of children eventually have five or fewer stools each day. Some children may experience constipation at some point, which is typically relieved with a mild laxative. Children are advised to drink plenty of fluids and to eat high-fiber foods in order to reduce episodes of diarrhea/constipation. Infants and children may also suffer the complication of enterocolitis; however, this is less common than diarrhea and constipation. Other than bouts of diarrhea/constipation, these children tend to live normal lives. Those with Downâ€™s syndrome have a higher incidence of complications following surgery. They have a higher risk of enterocolitis and a risk of suffering adverse cardiovascular events.
Cell of Origin: neural crest cells
Associations/Predisposing Factors: Down's syndrome, Onidine's curse, MEN 2, Waardenburg syndrome
Common Locations: rectosigmoid, splenic flexure, entire colon
Demographics: white female
Radiology: transition zone separates the narrowed, aganglionic colon from the proximal, dilated, innervated colon
Prognosis and Treatment: pull through surgery