Congenital Megacolon

Congenital aganglionic megacolon (Hirschsprung's disease) is caused by the absence of intestinal innervation that affects the internal anal sphincter and the adjacent proximal segment.

Epidemiology

 * It is the most common cause of lower GIT obstruction in newborns;
 * its incidence is 1:5000 live births;
 * boys are affected 4 times more often than girls;
 * and it may be associated with other birth defects (i.e: trisomy 21 or medullary thyroids carcinoma).

Etiopathogenesis and Pathophysiology

 * a disorder of neuroblast migration from the proximal to the distal intestine with consequent absence of ganglion cells in the intestinal wall;
 * histologically: absence of Meissner's and Auerbach's plexus with hypertrophic nerve endings and high concentration of acetylcholinesterase;
 * short-segment disease aka the classical form(75%): aganglionosis in the rectosigmoid colon;
 * long-segment disease (10%): aganglionosis in the whole colon
 * ultra-short segment disease: aganglionosis in the rectum that is 1-3 cm long;
 * the aganglionic region is permanently contracted (inhibiting neurons are missing) which causes a functional obstruction → thus, the healthy intestine dilates above it and hypertrophies to form a megacolon.

Clinical Picture

 * in 90% of cases, manifestation begins immediately after birth;
 * milder forms: chronic constipation, growth failure, gradually developing abdominal distension with an increase in pathogens and symptoms of enterocolitis to sepsis;
 * the onset of difficulties is typical in infancy (often after the introduction of non-dairy foods): increased tone of the internal sphincter, small volume of stool during defecation, or no defecation;
 * in ultrashort segment disease, stools accumulate in the rectum and the sphincters gradually weaken. Thus smearing + paradoxical diarrhea (soiled laundry).

Diagnosis



 * irigography – after previous emptying of the intestine by enemas, delayed evacuation, transition zone between the narrow distal aganglional segment and the proximally dilated section of the intestine; defecogram;
 * anorectal manometry - measurement of anal pressure when inflating a balloon in the rectum (anal pressure does not decrease or it paradoxically increases);
 * rectal biopsy - may be false negative in the ultrashort segment.

Therapy

 * surgical solution: good prognosis, most patients have preserved continence.

Complications

 * Toxic megacolon - can lead to sepsis with a risk of secondary meningitis or intestinal perforation.

Related Articles

 * Congenital atresia and stenosis of the gastrointestinal tract
 * congenital hypertrophic pyloric stenosis
 * superior mesenteric artery sydrome
 * intestinal malrotation and volvulus
 * small intestine obstruction
 * meconium ileus