Intussusception occurs when a segment of the intestine, constricted by a wave of peristalsis, telescopes into the immediately distal segment. Once trapped, the invaginated segment is propelled by peristalsis and pulls the mesentery along. Untreated intussusception may progress to intestinal obstruction, compression of mesenteric vessels, and infarction. Intussusception is the most common cause of intestinal obstruction in children younger than 2 years of age. There usually is no underlying anatomic defect and the child is otherwise healthy. Other cases are associated with viral infection and rotavirus vaccines and may be related to reactive hyperplasia of Peyer patches, which can act as the leading edge of the intussusception. Contrast enemas are diagnostically useful and also are effective in correcting idiopathic intussusception in infants and young children. However, surgical intervention is necessary when an intraluminal mass or tumor serves as the initiating point of traction, as is typical in older children and in adults.
Hirschsprung disease occurs in approximately 1 of 5000 live births and stems from a congenital defect in colonic innervation. It may be isolated or occur in combination with other developmental abnormalities. It is more common in males but tends to be more severe in females. Siblings are at increased risk for development of Hirschsprung disease.
Patients typically present as neonates with failure to pass meconium in the immediate postnatal period followed by obstructive constipation. The major threats to life are enterocolitis, fluid and electrolyte disturbances, perforation, and peritonitis. Surgical resection of the aganglionic segment with anastomosis of the normal colon to the rectum is effective, although it may take years for patients to attain normal bowel function and continence.
The enteric neuronal plexus develops from neural crest cells that migrate into the bowel wall during embryogenesis. Hirschsprung disease, also known as congenital aganglionic megacolon, results when the normal migration of neural crest cells from cecum to rectum is disrupted. This produces a distal intestinal segment that lacks both the Meissner submucosal plexus and the Auerbach myenteric plexus (“aganglionosis”), and thus fails to develop coordinated peristaltic contractions. Mutations in the receptor tyrosine kinase RET account for a majority of familial cases and approximately 15% of sporadic cases. Mutations in other genes, including disease-modifying genes, as well as environmental factors must also be involved.
Hirschsprung disease always affects the rectum, but the length of the additional involved segments varies. Most cases are limited to the rectum and sigmoid colon, but severe disease can involve the entire colon. The aganglionic region may have a grossly normal or contracted appearance, while the normally innervated proximal colon may undergo progressive dilation as a result of functional distal obstruction (
Fig. 15.19 ). Diagnosis is made by demonstrating the absence of ganglion cells in the affected segment.
Fig. 15.19 Hirschsprung disease. (A) Preoperative barium enema study showing constricted rectum (bottom) and dilated sigmoid colon. Ganglion cells were absent in the rectum, but present in the sigmoid colon. (B) Corresponding intraoperative appearance of the dilated sigmoid colon. (Courtesy of Dr. Aliya Husain, The University of Chicago, Chicago, Illinois.)