bubble_chart Overview

Congenital megacolon (Hirschsprung's disease) is a common congenital intestinal malformation in children, caused by persistent spasm of the distal rectum or colon, leading to fecal stagnation in the proximal colon, which results in hypertrophy and dilation of the affected intestine. From 1955 to 1991, the Department of Surgery at Beijing Children's Hospital treated a total of 1,439 cases, including 599 newborns, with a male-to-female ratio of 4:1. The condition has a hereditary tendency.

bubble_chart Etiology

The fundamental pathological change in congenital megacolon is the absence of ganglion cells in the myenteric and submucosal plexuses of the intestinal wall, along with an increase in the number and thickness of unmyelinated parasympathetic nerve fibers. Hence, congenital megacolon is also termed "aganglionosis." Due to the absence or reduction of ganglion cells, the affected intestinal segment loses normal propulsive peristalsis and remains in a state of spasm, leading to functional intestinal obstruction and difficulty in fecal passage. The proximal segment of the spastic intestine gradually dilates and thickens due to chronic fecal accumulation, resulting in megacolon. In reality, the primary pathological change occurs in the spastic segment. In approximately 90% of cases, the aganglionic segment is located in the rectum and distal sigmoid colon, while in rare cases, it may involve the entire colon, terminal ileum, or only the distal rectum. During the neonatal period, spasm of the affected intestinal segment often leads to extreme dilation of the entire colon or even the small intestine, accompanied by recurrent symptoms of complete intestinal obstruction. As the child grows older, the thickening and dilation of the colon become more pronounced and localized.

bubble_chart Clinical Manifestations

1. Delayed passage of meconium, intractable constipation, abdominal distension, and fullness: The clinical manifestations vary depending on the length of the affected intestinal segment in the child. The longer the spastic segment, the earlier and more severe the constipation symptoms appear. Most cases involve no passage of meconium within 48 hours after birth or only a small amount, and low or even complete intestinal obstruction symptoms may develop within 2–3 days, including vomiting, abdominal distension, and fullness, with no bowel movements. For cases with shorter spastic segments, a digital rectal examination or warm saline enema can lead to the expulsion of a large amount of meconium and gas, alleviating symptoms. However, for cases with longer spastic segments, obstruction symptoms are often difficult to relieve and may sometimes require emergency surgical treatment. Even after the relief of intestinal obstruction symptoms, constipation and abdominal distension and fullness persist, necessitating frequent anal dilation and enemas to facilitate bowel movements. In severe cases, the condition progresses to the point where bowel movements are impossible without enemas, and abdominal distension and fullness gradually worsen.
2. Malnutrition and developmental delay: Prolonged abdominal distension and constipation can reduce the child’s appetite, impairing nutrient absorption. Fecal accumulation leads to thickening and dilation of the colon, resulting in a broad, large intestine-shaped abdomen. Sometimes, fecal-filled intestinal loops and fecaliths can be palpated.
3. Hirschsprung's disease-associated enterocolitis: This is the most common and severe complication, particularly during the neonatal period. The exact etiology remains unclear, but it is generally believed that long-term distal obstruction, proximal colonic hypertrophy and dilation, and poor intestinal wall circulation are underlying factors. On this basis, some children develop enterocolitis due to abnormal immune function or allergic constitution. Others suggest bacterial or viral infections as the cause, though stool cultures often show no pathogenic growth. The colon is the primary affected site, with mucosal edema, ulcers, and localized necrosis. When inflammation invades the muscular layer, it can manifest as serosal congestion, edema, thickening, and intraperitoneal exudation, leading to exudative peritonitis. The child’s overall condition suddenly deteriorates, with severe abdominal distension, vomiting, and sometimes diarrhea. Due to diarrhea and the accumulation of large amounts of intestinal fluid in the dilated colon, dehydration, acidosis, high fever, rapid pulse, and hypotension may occur. Without timely treatment, this can lead to a high mortality rate.

bubble_chart Diagnosis

1. Medical history and signs: More than 90% of infants fail to pass meconium within 36–48 hours after birth, followed by a history of persistent constipation, abdominal distension, and fullness. Bowel movements can only be achieved through enemas, laxatives, or anal suppositories. Malnutrition, anemia, and loss of appetite are common. The abdomen is highly distended with visible wide intestinal loops. Digital rectal examination reveals an empty rectal ampulla with no palpable stool; feces are only palpable beyond the spastic segment in the dilated segment.
2. X-ray findings: Abdominal upright plain films often show low colonic obstruction. Barium enema lateral and anteroposterior views reveal typical spastic and dilated intestinal segments with poor barium expulsion. Barium retention persists even after 24 hours. If deficient, washing out the barium via enema may lead to the formation of barium stones. In cases complicated by enteritis, the dilated intestinal wall shows a serrated appearance. In neonates, dilated intestines may only become visible for contrast after two weeks. If the diagnosis remains uncertain, the following examinations are performed.
3. Biopsy: A small tissue sample is taken from the submucosal and muscular layers of the rectal wall, 4 cm above the anus, to assess the number of ganglion cells. Children with Hirschsprung's disease lack ganglion cells.
4. Anorectal manometry: This measures reflex pressure changes in the rectum and anal sphincter, aiding in the diagnosis of congenital megacolon and differentiating it from other causes of constipation. In normal children and those with functional constipation, the internal sphincter immediately relaxes reflexively upon rectal distension, leading to a pressure drop. In contrast, children with congenital megacolon show no relaxation of the internal sphincter; instead, it contracts significantly, increasing pressure. This method may yield false-positive results in neonates within the first 10 days of life.
5. Rectal mucosal histochemical examination: This is based on the absence of ganglion cells in the submucosal and muscular layers of the spastic segment, where hypertrophied preganglionic parasympathetic fibers continuously release large amounts of acetylcholine and cholinesterase. Chemical methods can detect levels and activity of these substances 5–6 times higher than in normal children, aiding in the diagnosis of congenital megacolon, even in neonates.

bubble_chart Treatment Measures

For cases with short spastic intestinal segments and mild constipation symptoms, comprehensive non-surgical therapy can be initially adopted. This includes regular enemas with isotonic saline (ensuring equal input and output volumes, avoiding hypertonic or hypotonic saline or soapy water), anal dilation, glycerin suppositories, mild laxatives, and acupuncture or Chinese medicinals to prevent fecal accumulation in the colon. If these methods prove ineffective, surgical treatment should be pursued even for short-segment Hirschsprung's disease.

For cases with long spastic intestinal segments and severe constipation, radical surgery is necessary. The most commonly performed procedures currently include:

1. pull-through rectosigmoidectomy (Swenson's procedure);
2. colon resection with retrorectal pull-through (Duhamel's procedure);
3. rectal mucosal stripping with colon pull-through within the rectal muscular sheath (Soave's procedure).

If the child develops acute small intestine colitis, crisis, or nutritional and developmental impairments and cannot tolerate a single radical surgery, intravenous fluid and blood transfusion should be administered to improve general conditions before proceeding with radical surgery. If the colitis cannot be controlled, and abdominal distension, fullness, and vomiting persist, an intestinal stoma should be promptly created, followed by radical surgery later.

bubble_chart Prognosis

Significant progress has been made in the diagnosis and treatment of congenital megacolon in recent years. If children can receive early diagnosis and timely surgical intervention, both short-term and long-term postoperative outcomes are generally satisfactory. However, some children may experience frequent bowel movements or incontinence after surgery, requiring extended periods of bowel training.

bubble_chart Differentiation

Congenital megacolon in newborns should be differentiated from intestinal obstruction caused by other reasons, such as low small intestine atresia, colonic atresia, meconium constipation, neonatal peritonitis, etc.

In older infants and children, it should be distinguished from rectal stricture of anus, secondary megacolon caused by intra- or extraluminal tumor compression, colonic inertia (such as constipation caused by hypothyroidism in children), habitual constipation, and idiopathic megacolon in children (which usually occurs suddenly after 2 years of age, caused by dysfunction of the internal anal sphincter, and mainly treated with comprehensive conservative therapy).

When complicated with small intestine colitis, it should be differentiated from viral or bacterial enteritis or septic intestinal paralysis.