The congenital megacolon was described in detail by Harold Hirschsprung in 1886, hence the name “Hirschsprung’s disease” (HD) after him. Congenital megacolon is a malformation characterized by the absence of ganglion cells in the intestinal wall. The ganglion cell-free segment of the colon is located at the distal end of the colon. The ganglion cell-free segment lacks propulsive peristalsis and the intestine is in a spastic state, causing incomplete or complete colonic obstruction in clinical practice. The ganglionless segment is located mainly in the rectum and part of the sigmoid colon, but can also involve any area from the hepatic region of the colon to the descending colon. The most common clinical manifestations of HD are abdominal distention, delayed fetal elimination, and vomiting. 50% to 90% of children with HD develop abdominal distention, bilious vomiting, and intractable constipation during the neonatal period. 10% of children with HD develop small bowel colitis caused by megacolon, which is characterized by fever, abdominal distention, and diarrhea, and may be recurrent and even fatal. HD does not involve the same length of colon, which determines the clinical manifestations of the disease, and the lack of a uniform gold standard for diagnosis makes preoperative confirmation difficult. The classic methods for diagnosing HD include barium enema, rectal anorectal manometry, rectal mucosal biopsy, acetylcholinesterase test, and rectal biopsy, which have their own advantages and disadvantages. Although barium enema is simple, it does not have a high confirmation rate for HD and may misdiagnose some of the giant colon homoeopathy (HAD) as HD. barium enema is an important sign for the diagnosis of HD if clear stenotic and dilated segments can be seen, and its accuracy rate is about 80%. Repeat films should be taken 24 hours later to observe barium retention in order to confirm the diagnosis and determine the extent of resection. No bowel preparation is required prior to barium enema examination. The barium injection catheter should be inserted just beyond the anal canal; excessive catheter insertion beyond the anal canal may lead to misdiagnosis. This is because the tip of the catheter may reach the dilated colon and result in the injection of contrast into the bowel above the ganglion cell-free segment. Rectal mucosal aspiration biopsy is currently considered the gold standard HD for diagnosis, and finding absent enteric ganglion cells or an excess of unmyelinated nerves can confirm the diagnosis. However, it is difficult to be widely used clinically, mainly because of the blindness of sampling, the difficulty of unifying the biopsy site and the thickness of the specimen in different cases, and the time consuming histological examination of rectal biopsy. Traditional full-thickness rectal biopsy is of high diagnostic value, but the rectum can only be well exposed in newborns under general anesthesia, so it is difficult to take the material. Suction biopsy, on the other hand, 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. Acetylcholinesterase (AchE) staining AchE staining tests are important for the diagnosis of HD and can be correct up to 99% of the time. Normal intestinal mucosa is negative for AchE, and AchE-positive nerve fibers are seen in the narrow segment of the intestinal canal of the lesion. This histochemical staining method can be done in a short time (within a few minutes) and is easy to apply clinically. Therefore, European and domestic scholars believe that the rectal mucosal biopsy AchE test can replace the histological examination of rectal mucosal aspiration biopsy and become the “gold standard” for the diagnosis of HD. Rectal anorectal manometry is also important for the diagnosis of HD, and the accuracy rate can reach 90%. However, this test is highly influenced by the external environment and is less accurate than the rectal mucosal biopsy AchE test. The test can detect internal sphincter failure, determine homozygosity for megacolon, and evaluate defecation function in postoperative patients, among others. Conclusion There are clearly different views on the reliability of various diagnostic methods. The most important thing is the experience of radiologists and pathologists. Barium enema is by far the most valuable diagnostic method. A biopsy of a specimen from the rectum can establish the diagnosis, but it does not show pathological changes in the migrated area. The range of valuable information needed to make a definitive diagnosis must be obtained radiologically, clinically, or through surgical full-thickness biopsy.