Congenital Megacolon

　　A decrease or absence of ganglion cells in the intermuscular plexus of the distal colon wall is the etiology of congenital megacolon.

　　The lesion is prone to occur at the junction of the sigmoid colon and rectum, with the length of the segment without ganglion cells extending from the rectum to the proximal end varying. It can be long, and in some individual cases, it can involve the entire colon. In rare cases, it can be very short. The segment without ganglion cells can be shown normally under gross or X-ray examination, so to determine whether there are ganglion cells, rectal biopsy is necessary. Due to the lack of normal peristalsis in the intestinal tract of the lesion site, it is often in a spasmodic state, forming a functional intestinal obstruction, making it difficult for feces to pass through. Since the feces cannot smoothly enter the rectum, the ampulla is often empty and cannot stimulate the receptors of the rectal wall to cause a normal defecation reflex. Therefore, the proximal part of the spasmodic intestinal tract, due to the long-term accumulation of a large amount of feces and gas, causes the intestinal wall to gradually thicken and the intestinal lumen to dilate, forming megacolon. Therefore, the main lesion of this disease is in the distal spasmodic intestinal segment, and the large colon is just the consequence of functional intestinal obstruction.

　　The gross anatomical findings of megacolon and clinical symptoms depend on the level of the lack of ganglion-containing intestinal tract and the age of the patient. In the neonatal period, the entire colon and even the small intestine may become extremely dilated due to spasm of the lesion segment of the intestinal tract, with thinning of the intestinal wall. However, due to the short course of the disease, there is no typical thickening of the intestinal wall as seen in megacolon. Occasionally, intestinal perforation may occur, most often in the cecum or sigmoid colon, which is the proximal end of the spasmodic narrowed segment. As age increases, the expansion and thickening of the colon become more obvious and tend to be localized.

　　Small bowel colitis is the most serious complication of congenital megacolon, which is more common in the neonatal period. The onset is acute, with high fever, vomiting, and diarrhea. The accumulation of a large amount of intestinal fluid in the obstructed intestinal lumen can lead to severe dehydration, acidosis, and shock, with a mortality rate as high as 30%. Other complications include intestinal obstruction, intestinal perforation, malnutrition, and developmental delay, etc.

　　The symptoms of congenital megacolon in newborns are the failure to excrete meconium, and in older children, it is characterized by obstinate constipation. The specific introduction is as follows:

　　1, Newborns and infants

　　Normal newborns almost all excrete the first meconium within 24 hours after birth. Infants may show symptoms of not excreting meconium after birth, with delayed excretion and emptying of meconium. Partial or even complete intestinal obstruction symptoms may appear within 2 to 3 days after birth. Infants may vomit, with vomit containing bile or fecal-like fluid, and have abdominal distension and constipation. Digital rectal examination or warm saline enema can expel a large amount of meconium and gas, relieving symptoms. After a few days of relief, abdominal distension and constipation may recur, and enema is needed again to defecate. Physical examination may be completely normal, and sometimes an expanded intestinal tract can be palpated transversely across the upper abdomen. If a right-to-left peristaltic wave is observed, it can be inferred that it is in the dilated transverse colon near the proximal end of the aganglionic intestinal segment. After abdominal distension is relieved, food can be consumed; however, most infants do not gain weight due to vomiting and refusal to eat, leading to poor development.

　　In neonates, diarrhea may also be the prominent symptom accompanied by intestinal obstruction, with frequent alternation of constipation and diarrhea. If it is recurrent and prolonged, the child becomes increasingly thin and malnutrition, leading to malnutrition edema. In the neonatal period, it is very common to have concurrent enteritis, which is often refractory and difficult to treat, and may develop into severe small and large bowel colitis. The onset is acute, with high fever, vomiting, diarrhea, and a large amount of intestinal fluid accumulated in the obstructed intestinal lumen can lead to severe dehydration, acidosis, and shock. If not actively rescued, most of them will die within 24 hours. The lesion of enteritis can produce peritoneal effusion, appear peritoneal irritation signs, and clinically resemble purulent peritonitis.

　　If the symptoms are mild, diagnosis is often not made during the neonatal period. During infancy, it is manifested as progressive constipation and abdominal distension. Mild cases often require laxatives for defecation, while severe cases often require enema to assist defecation. Children have developmental and nutritional levels below normal standards, significant abdominal distension, varicose veins on the abdominal wall, and often appear intestinal patterns. An intestinal loop filled with feces can be felt in the lower left abdomen.

　　2. Older children and adults

　　Some older children and adults have good tolerance for this disease and can live to a relatively old age. Chronic constipation is the main history, and some have a bowel movement only once every two weeks, often relying on laxatives for defecation, and the laxatives are becoming less effective. Physical examination shows pale complexion, malnutrition, protruding abdomen, and long, thin legs. Acute intestinal dysfunction may be seen occasionally. Patients develop complete intestinal obstruction and seek medical attention.

　　Congenital Hirschsprung's disease is an innate disease with no effective preventive measures. The diagnosis and treatment of this disease have made great progress in recent years. If the child can receive early diagnosis and early surgical treatment, the short-term and long-term effects after surgery are relatively satisfactory. However, some children may have frequent bowel movements or incontinence after surgery, and it may take a relatively long time to train defecation. The incidence of congenital Hirschsprung's disease is high, the patients are usually young, the surgery is relatively complex, and there may be many postoperative problems, so it is recommended that patients choose a specialized hospital with a certain level of technical standards for surgery to avoid difficulties in later treatment.

　　Congenital Hirschsprung's disease children can be examined by anal-rectal manometry, the method is to inflate the balloon in the anal ampulla, and it can be seen that with the rise of internal pressure, the normal infant's internal sphincter begins to relax, while the internal sphincter of the Hirschsprung's disease child remains contracted without relaxation reflex. Other auxiliary examinations for congenital Hirschsprung's disease children include:

　　1. Barium enema X-ray examination

　　After a small amount of barium enema is administered and anteroposterior and lateral films are taken, typical spastic intestinal segments and dilated intestinal segments can be displayed; the transitional area shows a saw-toothed change, which is due to the strong intestinal peristalsis causing the barium enema shadow to present irregular contraction rings, and the barium cannot be evacuated.

　　2. Rectal biopsy

　　For neonates suspected of having Hirschsprung's disease but not diagnosed by X-ray examination, rectal biopsy can also be performed to assist in diagnosis. Currently, there are mainly two methods of biopsy:

　　1. Tissue morphological method, observing the changes of ganglion cells and pre-ganglionic fibers.

　　2. Tissue chemistry examination, mainly to determine the activity of acetylcholinesterase.

　　Patients with congenital megacolon usually fast for 1-2 days after surgery. During the fasting period, fluids are infused on average within 24 hours, and the infusion rate is adjusted according to urine output. Nutrients and fat emulsions, etc., are given in small amounts and in multiple doses if necessary.

　　After the intestinal peristalsis recovers, a small amount of water is given, and if there is no distension or abdominal pain for 24 hours, breastfeeding or a liquid diet can be resumed, and then semi-liquid diet, gradually recovering to ordinary food. Start with small meals and gradually increase the amount. Pay attention to a diet rich in high protein, nutrition, and high calories, and easy to digest.

　　Congenital megacolon is treated with different methods based on the severity of the child's symptoms. Conservative treatment is adopted for mild cases, while surgical treatment is required for severe cases.

　　1. Medical treatment

　　For children with mild congenital megacolon or systemic infection symptoms who cannot tolerate surgery, non-surgical therapy can be used to maintain nutrition and development. Use laxatives or use physiological saline enemas at regular intervals to avoid fecal retention.

　　2. Colostomy

　　When children develop acute intestinal obstruction, or have tendencies towards intestinal perforation, peritonitis, or are accompanied by small intestinal and colitis, or have aganglionic colitis, colostomy should be performed. The colostomy site should be as close as possible to the expanded intestinal tract for a single stoma colostomy.

　　3. Surgical treatment

　　Newborn patients should be treated conservatively as much as possible, and radical surgery should be performed around 1 year of age. In adults, if symptoms worsen and conservative treatment is ineffective, radical surgery should also be performed. Radical surgery requires excision of the narrow rectum above 1-2 cm from the anal dentate line and the expanded colon above 5 cm. The commonly used surgical methods include the following three:

　　(1) Excision of the protruding rectum and sigmoid colon (Swenson surgery).

　　(2) Colectomy, sigmoid colon drawn out from the rectum (Duhamel surgery).

　　(3) Rectal mucosal stripping, excision of the colon drawn out from the rectal muscular layer (Soave surgery).