Congenital megacolon, also known as Hirschsprung’s disease, is one of the common congenital intestinal disorders in pediatric patients and can have a lasting effect on growth and development due to a lack of ganglion cells in the colon resulting in persistent spasm of the intestinal canal, stagnation of feces in the proximal colon, and hypertrophy and dilation of the proximal colon. I. Pathophysiology and embryology Congenital megacolon is a malformation characterized by partial or complete colonic obstruction combined with ganglion cell agenesis in the intestinal wall. The ganglion cell-free segment of the colon is located at the distal end of the colon, but the length of the colon involved is not the same, which determines the clinical presentation of the disease. The so-called “classic” and most common congenital megacolon has an anaplastic segment that includes the rectum and part of the sigmoid colon; the long segment megacolon accounts for approximately 10% of cases, and the anaplastic segment can involve any area from the hepatic region of the colon to the descending colon; the anaplastic segment of the total colon covers the entire colon and is often of different The whole colon type of megacolon without ganglion cell segments involves all of the colon and often the ends of the ileum of different lengths are involved, accounting for about 10% of all cases; the ultra-short or short segment type of congenital megacolon is often misdiagnosed as chronic functional constipation. Congenital megacolon is a disorder of neural crest origin, in which ganglion cells from the neural tube of the neural crest originate and migrate from the cephalic to the caudal side along the vagal fibers, first entering the upper gastrointestinal tract and migrating down the distal intestinal canal, and if this cephalic and caudal migration process is halted, the result is an absence of ganglion cells in the intestinal wall, which results in the Auerbach’s intermuscular plexus ( The result is the absence of ganglion cells in the Auerbach intermuscular plexus (located between the circular and longitudinal muscles of the intestinal wall), the Henle plexus (located in the deep submucosa) and the Meissner plexus (located in the superficial submucosa). Under normal conditions, ganglion cells are the final common pathway for sympathetic and parasympathetic regulation, and in diseased segments of the intestine, the absence of such cells may produce uncoordinated contractions of the intestine. These pathophysiological changes cause incomplete or complete colonic obstruction, and a series of common clinical symptoms and signs as a result. Clinical manifestations and differential diagnosis Children with congenital megacolon usually develop symptoms 24-48 hours after birth. Occasionally, children have only mild or no clinical symptoms during the first few days or weeks of life. Subsequently, moderate, intermittent episodes of clinical symptoms occur. The most common clinical manifestations of congenital megacolon are constipation, abdominal distention, delayed expulsion of fetal stool, and vomiting. These symptoms may be spontaneously or induced by an “explosive” mass of watery stool and gas, followed by a marked improvement in the patient’s general condition. In the following hours or days, the symptoms are relatively mild. Subsequently, the same clinical symptoms reappear. The stools are usually watery with a foul odor. When abdominal distention is marked, the patient is prone to sepsis, hypovolemia and endotoxic shock, and is usually in extremely critical condition. The most serious complication is a localized ischemic necrotizing small bowel colitis in the proximal part of the ganglion cell-free segment. Other complications include intestinal pneumatosis (the presence of thin-walled air sacs within the intestinal wall), pericolonic abscesses, and perforation of the cecum. If not diagnosed and treated promptly, the mortality rate is 25-30%. The differential diagnosis includes any disease that causes intestinal obstruction during the neonatal period, the most common being the so-called fetal fecal plug syndrome. Diagnosis is facilitated by the disappearance of symptoms after the fetal fecal plug is expelled, as well as by the absence of other clinical manifestations characteristic of congenital megacolon. The clinical manifestations of fetal fecal obstruction are often accompanied by respiratory symptoms in addition to intestinal obstruction. There may be a family history of cystic fibrosis. On x-ray, there is no air-fluid plane in the right upper abdomen, and the characteristic presentation is a hairy glassy appearance of the lower abdomen. Another disorder that is easily confused in the differential diagnosis is small left colon syndrome. Barium enema examination confirms significant stenosis of the left hemicolectum to the colonic spleen. Symptoms usually resolve after the barium enema examination and disappear completely after several weeks. Patients with congenital megacolon who survive without formal treatment or who have relatively mild symptoms at the time will eventually present with the typical clinical picture described above. These patients have extreme abdominal distention with severe constipation. The proximal colon is extremely dilated and filled with dry feces. At this stage, congenital megacolon may be confused with chronic constipation. Patients with chronic constipation usually present after 6 months of life without vomiting and without significant worsening of the condition. A very important feature of this group of patients is filling incontinence or incontinence – a chronic persistent fecal soiling without evidence of neuromuscular abnormalities. Rectal examination may reveal a large amount of fecal matter held above the anus. In contrast, the rectum may be empty in patients with megacolon, or only a small amount of feces may be found in the rectum on examination. Diagnosis 1. X-ray examination In neonatal intestinal obstruction, it is extremely difficult to distinguish small intestine dilatation or colon dilatation by ordinary abdominal plain film, so plain film examination can only diagnose suspected congenital megacolon. The presence of an air-fluid plane indicates the presence of intestinal obstruction, but it is nonspecific. The most valuable x-ray for the diagnosis of congenital megacolon is an enema with appropriately diluted barium or water-soluble contrast. No bowel preparation is required prior to the barium enema examination. The child is placed in the lateral position and the barium injection catheter should be inserted at a depth just beyond the anal canal. The rate of contrast injection is controlled by a syringe. If the catheter is inserted too deeply beyond the anal canal, this may lead to misdiagnosis. This is because the tip of the catheter may reach the dilated colon and inject contrast into the bowel above the ganglion cell-free segment. The contrast should be observed while injecting until it reaches the dilated portion of the intestine. This concludes the examination. If too much contrast, especially barium, is injected, it may result in incomplete evacuation of the contrast later and formation of a barium stone obstruction. This exam can show a proximal, extremely dilated colon, a migrated area and a distal spastic rectosigmoid colon. In older children, there is a significant difference in the diameter of the normal segment of the intestine with ganglion cells compared to the diseased intestine without ganglion cells. However, the typical radiographic appearance of congenital megacolon with barium enema is sometimes not seen in the neonatal period. After a few days or weeks, a second barium enema may be performed. This time, the lesions in the giant colon canal can be more clearly visualized than in the previous examination. However, most neonatal patients generally show the migrated area. In small infants with very short segments of megacolon or when all of the colon is involved, barium enemas are not very confirmatory. In total colonic megacolon, barium enema reveals a short colon with retraction of the hepatic and splenic flexures and a rigid sigmoid colon. In normal conditions when the rectum is dilated by a balloon, a rectoanal reflex is produced, i.e., a decrease in pressure in the anal canal due to relaxation of the internal sphincter. Whereas in children with congenital megacolon the rectoanal reflex is absent, although this reflex abnormality has been used as a diagnostic indicator, there are still some limitations, mainly the technical difficulty in diagnosing neonatal patients. In the authors’ experience, this test is mainly indicated in older children. 2. Rectal biopsy The diagnosis can be established by finding a lack of ganglion cells or an excess of unmyelinated nerves in a rectal biopsy taken from a sufficiently large specimen. Traditional full-thickness rectal biopsy is of high diagnostic value, but in the neonatal period the rectum can only be well exposed under general anesthesia, so it is difficult to take the specimen. In contrast, attraction biopsy has been widely accepted. This method is simple to perform, does not cause intestinal perforation, and does not require anesthesia. The specimen is usually 1 mm × 3 mm and should include the mucosa and submucosa. Pathological examination of the specimen should be performed by an experienced specialist. Another test for the diagnosis of congenital colonization is designed based on the presence of large amounts of acetylcholinesterase in the mucosa and submucosa of the diseased intestinal canal. It is characterized by the absence of thiosemicarbazone dehydrogenase neurons of reduced nicotinamide adenine dinucleotide phosphate (NADPH) and a large increase in acetylcholinesterase-positive nerve bundles. In addition, the progressive understanding of nitric oxide synthase has contributed to the diagnosis. Nitric oxide synthase is a neuromediator that causes relaxation of the internal anal sphincter and is an extremely important method for diagnosing short-segment megacolon. The choice of examination method has distinctly different views on the reliability of the various diagnostic methods. The most important is the experience of radiologists, physiologists, and pathologists. For us, barium enema is at least the most valuable diagnostic method. Also, rectal suction biopsy is used to verify the clinical and radiographic diagnosis. Biopsy of a specimen taken from the rectum can establish the diagnosis, but it does not show pathologic changes in the migrated area. A definitive diagnosis requires a range of valuable information that must be obtained radiologically, clinically, or through surgical full-thickness biopsy.