First, etiology
The normal process of intestinal tract development is divided into3stages: ① Duct opening stage, the small intestine has formed a patent duct in the early stage of the embryo. ② Epithelial cell proliferation stage, the embryo5~10week, the epithelial cells proliferate and multiply, causing the lumen to close, forming a temporary filling phase. ③ Re-formation stage, the embryo11~12week is completed, many bubbles appear in the occluded intestinal tract, fusing with each other, making the lumen patent again. If the development of the embryo's intestinal tract in the2or the3During the month, if a segment does not appear a bubble, it stays in the solid phase, or if a bubble appears but does not fuse with each other, or if fusion is incomplete, it will form an atresia or stenosis of the intestinal tract. Some people believe that if the blood circulation of the intestinal tract in the fetus is obstructed, it can also cause atresia. If the umbilical ring contracts too quickly, the embryo8The gastrointestinal tract before the fetus is straight, and then the intestinal tract develops quickly, and the peritoneal cavity expands slowly, causing the small intestine to become curved, the peritoneal cavity cannot accommodate it, and it protrudes into the umbilical vesicle.10~12The peritoneal cavity is enlarged, the protruded midgut rotates counterclockwise, and it is returned to the peritoneal cavity. The umbilical ring contracts before return, affecting the blood circulation of this segment of the small intestine, causing atrophy, and developing into stenosis or atresia. If the small intestinal nutrient vessels are abnormal, there are defects or branched malformations, or intussusception occurs, maldevelopment can occur.
Second, pathogenesis
1、The site of congenital duodenal atresia can be located at any part of the duodenum, but it is most common around the common bile duct, pancreatic duct, and ampulla, and the lesion is mostly located in the second segment of the duodenum around the ampulla. It is generally believed that the lesions distal to the ampulla are more common than those proximal to it.
2、Pathological types Congenital duodenal atresia is common4Types:
(1)Blind tube type: The proximal end of the duodenum terminates in an abnormally dilated blind tube, the distal end is small and separated from the proximal end, and the continuity of the intestinal tract is lost.
(2)Tie type: Both the proximal and distal ends of the duodenum are blind and closed, connected by fibrous bands, and this type is the rarest.
(3)Blind bag type: Although the proximal and distal ends of the duodenum are connected, there is a blind bag in the middle, the lumen is not patent, and there is a significant difference in diameter between the proximal and distal ends.
(4)Diaphragmatic type: This type is the most common, accounting for the majority of duodenal atresia85%~90%. Characteristics include the continuity of the intestinal tract, but at the2or the}}3There is a diaphragm in the intestinal lumen of the section, shaped like a web, which can be a single diaphragm or multiple diaphragms, most located near the Vater papilla, causing varying degrees of duodenal obstruction. There is a small hole in the center or edge of the diaphragm, the diameter of which is as thick as a probe, making it difficult for food to pass through. The diaphragm without a hole causes obstruction at birth, while the diaphragm with a large hole may have no symptoms or mild symptoms. Krieg(1937) have collected cases of congenital duodenal diaphragm21Cases, of which18Cases have been statistically analyzed on the relationship between the presence, size, and onset time of the diaphragm holes, showing that the larger the hole in the diaphragm, the later the symptoms appear. Some symptoms appear in childhood or adulthood. Although anatomically it is incomplete obstruction, functionally it is actually equivalent to atresia; sometimes the diaphragm is complete, and it is also atresia in anatomy, and in some cases the diaphragm can prolapse to the3within the section.
3Pathological changes in the atresia type cause complete obstruction, the duodenum and stomach proximal to the obstruction dilate, which can be several times larger than the normal diameter, the intestinal wall thickens, and peristalsis decreases; the duodenum distal to the obstruction becomes small and thin, in cases of complete atresia, there is no gas in the lumen, it is thinner than chopsticks, and the wall is very thin. If it is a perforated diaphragm type, it causes incomplete obstruction, the proximal intestinal tract becomes thickened, and the degree of dilatation is related to the degree of stenosis of the intestinal lumen and the duration of the disease.