The nature of the digestive tract is a peristaltic tube that pushes food forward through a processing plant, taking the best and leaving the worst, and finally expelling the waste out of the body.
Above: food through the tube: mouth – esophagus – stomach – duodenum – jejunum – ileum – colon – rectum – anal canal
Above: The innermost irregular projection of the intestine is the mucosa, and outward in order: the submucosa, the smooth muscle layer (circular and longitudinal muscles), and the outermost plasma membrane. The peristalsis of the intestine is the driving force for the advancement of its contents. Why does the intestine move peristaltically? Because there are muscles on the intestine that contract.
Above: A cross-sectional schematic of the intestine, where the nerves can be seen under the mucosa and between the cricoid longitudinal muscles respectively, with ganglion cells inside. Why do the muscles contract? Because there are nerves innervating it.
Above: A three-dimensional diagram is given to further understand the normal structure of the intestinal tube. The nerves of the intestinal canal are an interconnected network. Its operation is usually automated and does not require the brain to intervene.
If there were no ganglion cells inside the intestine, then there would be problems with the peristalsis of this intestine. Does this happen in reality? Yes, this is what happens in congenital megacolon.
Above: Congenital megacolon (Hirschsprung’s Diease) is the absence of intermuscular and submucosal ganglion cells in the intestinal wall.
Where do the ganglion cells in the intestine come from? We have to go back to the embryonic period.
Above: Ganglion cells come from the neural crest and are progressively distributed along the digestive tract from top to bottom. Several genes have been identified to be involved in this process
Above: Around the 8th to 10th week of embryonic life, ganglion cells are distributed from the top to the bottom of the colon. If something happens during this time and the ganglion cells don’t continue down the line, or if they do, they don’t survive, you end up with no ganglion cells at the end of the intestine.
It is easy to understand that the end of the intestine without ganglion cells is always at the end of the rectum, but the beginning is not necessarily at the top. (Below)
A: Common type (75%), no ganglion cells in the rectosigmoid colon; B: Short or very short type (3%-5%), no ganglion cells only in the end of the rectum; C: Long type (15%), beyond the sigmoid colon, up to the transverse colon; D: Total colon type (5%); E: Total colon and part of the small intestine type (rare). It can even reach the duodenum (extremely rare).
The above diagram is only used as an illustration for classification purposes, but a more accurate diagram of congenital megacolon would actually look like this (below).
Or it could look like this (below).
Because, the intestinal canal without ganglia is so tiny and stiff that stool cannot pass smoothly here, the intestinal canal above the diseased canal expands due to the accumulation of stool and presents a giant colon. This is the origin of the name of congenital megacolon.
However, we now know that this name is inaccurate and that it is not only the large part but also the narrow part below that is problematic. In 1887, a pathologist described the disease so accurately that it was named after him: Hirschsprung’s Diease.
This should be the name of the disease that is used worldwide without any ambiguity.
Ganglion cells are required to be seen under a microscope, so let’s get acquainted. (Below)
Above.
Top: Normal colon, the black box shows the interosseous nerve from which the ganglion cells surround.
Lower: congenital megacolon, no plexus or ganglion cells are seen between the muscles.
There are some specimens of congenital megacolon in which thickened nerves can also be seen. (see below)
Top: Two bundles of thickened nerves in the center of the picture, yet no ganglion cells, still congenital megacolon.
Above: After staining with cholinesterase, the congenital megacolon lesion intestine will show a lot of positivity in the submucosal lamina propria (transverse brown band in the middle of the picture)
Therefore, the gold standard diagnosis of congenital megacolon still relies on pathological examination.
In clinical practice, we encounter patients with symptoms that appear to be congenital megacolon, but pathological sections show ganglion cells that are not completely normal, showing abnormalities such as reduced (sparse) or immature or dysplastic ganglion cells. This group of patients is collectively referred to as congenital megacolon and its rim-like disease. Congenital megacolon and its rim-like disorders are also collectively referred to as enteric neuronal developmental abnormalities. The specific classification is more problematic and controversial. There is still a lot of controversy in medical development today, so it is normal for different doctors to give different opinions.
Above: The distribution of enteric ganglion cells, in addition to the question of presence and absence, there is also the question of number and specific morphology. These are also formed in the embryonic period.
These are the patients who will show a defecation disorder. For the sake of presentation, since this is a scientific article and does not want to involve academic arguments, we will limit the content to congenital megacolon first.
There is approximately 1 case of congenital megacolon in every 5000 live births. There are more males than females.
Trisomy 21 has a higher risk of congenital megacolon. People with a family history of congenital megacolon (e.g., parents, siblings) also have a higher chance of developing the disease. These are genetically related.
In terms of clinical presentation, the nature of congenital megacolon is a very specific type of bowel obstruction. Delayed defecation, difficult defecation, constipation; the above stool can not get down and will show abdominal distension, severe vomiting, and over time will cause malnutrition; intestinal tube and prone to inflammation, fever, and even intestinal perforation; intestinal tube dilatation stool retention for a long time, and the formation of fecal stones, further aggravating the obstruction.
The congenital megacolon with small bowel colitis or intestinal perforation is very, very serious and can be life-threatening!
There are different subtypes, different degrees of severity, and different symptomatology at different ages.
Neonatal: About 80% of congenital megacolon will manifest in the neonatal period. The absence of fetal stools for 24-48 hours after birth and abdominal distention should be thought of, but not only. In other children, it is straightforward to present with small bowel colitis and intestinal perforation. A biopsy should be taken when possible during the dissection.
Above: Abdominal distention
Older children: prolonged constipation, not even pooping without a cork. Chronic abdominal distention and poor nutritional status.
Above: Abdominal distension
Adults: In some cases, the symptoms are not very severe and may not even be diagnosed until the adult.
All parents can do is to take their children to a specialist when they need to be seen.
The diagnosis, first and foremost, is still based on signs and symptoms.
Above: A mass is felt in the abdomen and CT shows a large fecal stone
When doing a rectal exam, experienced doctors always stand on the side of the child because the moment the finger exits, there is a high probability of a blasting bowel movement that can’t be avoided. The picture is too beautiful for me to describe.
There are only three auxiliary tests: barium enema, rectal anal canal manometry and rectal biopsy.
Above: Barium enema: Under the X-ray, the white barium shows the shape of the colon clearly. I don’t need to point out the stenotic segment and dilated segment, but the transitional segment between them is called the migrated segment.
Above: Rectal anal canal manometry. The principle is that when there is stool in the rectum, the anal canal relaxes so that the stool can come out. A balloon is placed in the rectum and water is injected to simulate the presence of stool, while the pressure of the anal canal is measured; if there is no relaxation reflex, there is a problem. The results in younger children are not always very reliable.
Above: This is a normal manometry result
Above: this would be consistent with congenital megacolon
There are two approaches to rectal biopsy: negative pressure suction biopsy and open biopsy. The former is simple and easy to perform, and the tissue can be taken to the submucosa, but if only the mucosa is taken, there is no diagnostic value. The latter can take deeper and larger tissues (submucosal and intermuscular) and is more reliable for diagnosis, but requires anesthesia.
Treatment.
Some measures before radical surgery: anal dilation, open cavity, reflux lavage (different from enema in adults!) , enterostomy, excavation of fecal stones (when I was a child I always thought that if I studied well I would not be a fecal emptier).
Surgery is generally not advocated during the neonatal period, but rather lavage, and if lavage does not work well, fistulas can be performed. This is not because surgery during the neonatal period is so difficult, but more for the sake of accurate diagnosis, so as not to be operated on if it should not be.
We emphasize the need to insist on bowel cleansing! Why? Because by insisting on bowel cleansing, the child can live a normal life, reduce complications such as enterocolitis and fecal stones, and nutrition can be ensured; in addition, avoiding dilatation of the intestine allows more of the intestine to be preserved and not removed. After training, parents can fully master the skilled technique of bowel cleansing.
Method of surgery.
Above: The surgery is to remove the area from the dentate line 1 cm up to where there are normal ganglion cells. The classic methods are: B, Swenson C, Duhamel and D, Soave.
The master, Prof. Lai Bing-Yiu’s Lai’s anastomosis (included in Wong Ka-Yiu Surgery) is a modification of the Swenson procedure. Nowadays, with the combined use of laparoscopy and transanal drag-out surgery, the modified Soave procedure is used more often.
In the treatment of congenital megacolon like rim disease, there is a tendency to be conservative and then surgical if conservative fails.
After surgery, routine anal dilation is required, as described in the pediatric dilation.
For a long time after surgery, the child may have problems with bowel movements, such as high frequency and redness of the perianal skin. Constipation or incontinence may also occur, so long-term follow-up is also required.
It is difficult to deal with those lesions with extra-long bowel tubes, either congenital megacolon or its analogous marginal disease. Surgeons have no problem cutting and dicing into the ganglion cell normal bowel, but not enough good bowel is really tricky. You know what? Doctors also have a helpless time.
One last thing: Are all megacolons congenital? No, megacolon can also be secondary, for example, after anal stenosis, the colon can also be dilated. The treatment is different.
Above: Flow chart of congenital megacolon diagnosis and treatment