Malrotation of the intestinal loop in children

　　1. Etiology

　　Understanding the embryonic development of the small intestine is of great significance for understanding and treating the disease surgically.

　　In the early stages of pregnancy, the development of the embryonic midgut is faster than the development of the body cavity. Therefore, by the fourth week of fetal development, the midgut usually protrudes into the abdominal cavity, forming an umbilical hernia; around the 10th week of pregnancy, the intestinal segments are retroperitonealized, gradually completing rotation and fixation, until finally forming the mature form of the small intestine and colon of a full-term baby. If the midgut is disturbed during the rotation process, corresponding clinical symptoms may appear after birth. The development of the midgut is divided into three stages.

　　1. The First Stage

　　An umbilical hernia forms. At 4 weeks of pregnancy, the fetal midgut begins to curve and protrude laterally, entering the umbilical cord cavity, forming a hernia. The hernia axis is the superior mesenteric artery (SMA), and it is used as a marker to divide the midgut into the cranial segment (anterior to the artery, duodenojejunal segment) and the caudal segment (posterior to the artery, cecum segment). In the first stage, the cranial segment of the midgut develops faster than the caudal segment.

　　(1) Development of the lateral segment: During the formation of the mesenteric hernia and the process of its growth outside the body cavity, the lateral segment is pushed downward by the developing liver and left umbilical vein, rotating counterclockwise 90° to the right of the SMA, as shown in Figure 1B; with the further development of the intestinal lumen, before the start of the second stage, the lateral segment rotates 90° again to the posterior of the SMA, totaling 180° rotation.

　　(2) Development of the caudal segment: In the first stage, the caudal segment of the mesentery rotates parallel to the lateral segment, and the ileocecal junction is initially located below the SMA, as shown in Figure 2A. Synchronous with the first 90° rotation of the lateral segment to the right of the SMA, the ileocecal junction rotates counterclockwise 90° to the left of the SMA. Before being returned to the peritoneal cavity at the 10th week, the ileocecal junction continues to rotate 90°, at this time it is exactly on the ventral side of the SMA.

　　2. Second stage

　　The mesentery is returned to the abdomen.

　　(1) Development of the lateral segment: The intestinal segment continues to develop and starts to return to the peritoneal cavity at 10 weeks of gestation (at this time, the embryo is about 40mm long) and is completed at 11 weeks. The lateral segment is first returned, during which it continues to rotate 90° around the SMA, totaling 270° counterclockwise rotation. Finally, the duodenojejunal junction is fixed to the left side of the posterior abdominal wall behind the Treitz ligament.

　　(2) Development of the caudal segment: During the process of the cecum and colon being returned to the peritoneal cavity, it also continues to rotate 90° to the right of the SMA, totaling 270° counterclockwise rotation around the SMA.

　　3. Third stage

　　The mesentery is fixed from the 12th week of pregnancy to birth. If the mesentery rotates normally, the colon gradually completes fixation, and the peritoneum forms a band-like tissue, that is, the ascending and descending colon mesentery is attached to the posterior abdominal wall. If the cecum and ascending colon do not rotate thoroughly and do not reach the right abdomen, the peritoneal band will still connect the ascending colon to the right colic fossa. At this time, the band crosses the ventral side of the duodenum, compressing the intestinal segment to cause obstruction.

　　Second, Pathogenesis

　　The main anatomical abnormality of poor rotation is still classified according to the lateral and caudal segments, and abnormal fixation usually only occurs in the cecum and colon.

　　1. Complete non-rotation

　　The most common clinical case is the complete non-rotation of the mesentery, that is, both the lateral and caudal segments do not rotate, as shown in Figure 4. Normally, the duodenum rotates behind the SMA, and the Treitz ligament is located on the left side of the median line at the level of the gastric antrum. If the mesentery does not rotate, the duodenum becomes shorter and appears spiral-shaped, completely located on the right side of the median line, causing incomplete duodenal obstruction; while the intestinal segments are not fixed, making the mesentery prone to torsion. The mesentery of the duodenum and colon wraps around the SMA and fuses into a mesentery pedicle, around which the mesentery twists. Normally, the base of the small intestinal mesentery is very wide, from the left upper abdomen to the right lower abdomen, the small intestine and mesentery generally cannot occur axial torsion; if the proximal jejunum and distal ileum are both located in the middle abdomen, the mesentery attachment is relatively narrow, the possibility of torsion increases significantly.

　　2. Abnormal rotation of the lateral segment

　　If only the lateral segment does not rotate, while the caudal segment rotates and is fixed normally, it can also cause duodenal obstruction due to the compression of the mesentery ligament band, as shown in Figure 5. However, since the mesentery attachment between the duodenojejunal junction and the ileocecal junction is still relatively wide, the possibility of mesenteric torsion is small.

　　3. The lateral segment rotates in the opposite direction

　　It leads to the duodenum being located in front of the SMA (it should be located behind normally); while the reverse rotation of the caudal segment leads to the transverse colon being located behind the SAM as shown in Figure 6, resulting in colonic obstruction. If the caudal segment rotates normally, as the ascending colon rotates from the left upper abdomen to the lower right abdomen, its mesentery crosses in front of the SMA, covering the small intestine developed from the cranial segment, forming a hernia sac, known as a duodenal hernia.

　　4. Incomplete rotation of the cranial segment

　　It leads to the position of the duodenojejunal junction (Treitz ligament) being lower than its normal position in the left upper abdomen; while abnormal rotation of the caudal segment can cause intestinal volvulus. In addition, there is no objective standard for distinguishing between non-rotation or incomplete rotation of the cranial segment, and it is generally believed that as long as the Treitz ligament is located on the right side of the abdominal midline, it is considered non-rotated.

　　5. Abnormal rotation of the caudal segment

　　If the cranial segment rotates normally but the caudal segment rotates abnormally, it can also cause intestinal volvulus. Similar to complete non-rotation, at this time, the attachment of the mesenteric root between the Treitz ligament and the ileocecal region is very narrow.

　　6. Incomplete rotation of the caudal segment

　　It may cause abnormal fixation of the colon, incomplete fixation of the ileocecal region may lead to volvulus of the cecum; while incomplete fixation of the hepatic flexure of the colon, there is a formation of peritoneal bands extending to the right upper posterior abdominal wall, leading to partial obstruction of the duodenum.

　　1. Malrotation or incomplete rotation of the intestine is often an important complication of congenital diaphragmatic hernia and abdominal wall defect - umbilical hernia, abdominal cleft. It is reported that 30% to 62% of children with malrotation have associated anomalies, most of which are gastrointestinal anomalies. 1/2 of duodenal atresia cases and 1/3 of jejunoileal atresia cases have associated malrotation, one of the causes being intracranial intestinal volvulus that obstructs mesenteric blood supply, leading to intestinal atresia. Other anomalies include: Meckel's diverticulum, duodenal valve or stenosis, megacolon, anal atresia, esophageal atresia with esophageal tracheal fistula, congenital short bowel, biliary atresia, congenital heart disease, visceral transposition, mesenteric cysts, and pelvic viscerosacral syndrome. There are reports of familial malrotation associated with facial or limb abnormalities, suggesting that the disease may be related to genetics.

　　1. Complications of this disease may include dehydration, acidosis, septic shock, peritonitis, and strangulated intestinal obstruction. If symptoms appear intermittently, they can lead to malnutrition and delayed growth and development.

　　1. Intestinal volvulus

　　Intestinal volvulus is more common in infants and children, but it can also occur in other age groups, even in adulthood, and is an emergency surgery. If not treated in time, it can lead to short bowel and death due to small bowel necrosis. The typical symptoms are sudden bilious vomiting in neonates, which is related to duodenal intussusception and compression by peritoneal bands. Intestinal obstruction, sepsis, and hemorrhagic intracranial hypertension can also cause bilious vomiting, and rapid differential diagnosis is required. It is currently impossible to predict when or under what circumstances intestinal volvulus will occur, so for children with bilious vomiting, active diagnosis and treatment must be carried out, and it is absolutely not allowed to only observe and allow it to develop into绞窄性肠梗阻. Once intestinal necrosis occurs, the chance of survival is greatly reduced, and it is extremely difficult to preserve a sufficient length of small intestine. Therefore, once malrotation is found, it should be corrected surgically.

　　2. Duodenal obstruction

　　Duodenal obstruction is caused by the failure of the cranial segment of the duodenojejunal loop to rotate around the SMA or incomplete rotation, resulting in duodenal flexure and torsion, causing intermittent obstruction. In addition, the congenital band from the ascending colon to the lateral posterior abdominal wall of the right upper quadrant can compress the duodenum, causing obstruction, with typical symptoms of bilious vomiting (occasionally non-bilious) and abdominal pain, or both.

　　3. Intermittent chronic abdominal pain

　　Patients with malrotation may experience intermittent or chronic abdominal pain, which can be caused by many factors and often coexist. Intermittent intestinal torsion or intestinal obstruction caused by other reasons can lead to intestinal腔 expansion, causing spastic pain and vomiting; partial or intermittent occlusion of the mesenteric venous or lymphatic system can cause edema of the intestinal wall, mesentery, and mesenteric lymph nodes. The above reasons can also cause abdominal pain, and partial torsion can also cause chronic arterial insufficiency, leading to diarrhea, chronic abdominal pain, postprandial intestinal colic, or black stools due to mucosal ischemia.

　　4. Asymptomatic patients

　　During abdominal surgery for other diseases or upper and lower gastrointestinal contrast examination, asymptomatic malrotation of the intestine can occasionally be found, and its pathological basis may be the complete non-rotation of the cranial and caudal segments, or the normal rotation of the cranial segment while the caudal segment does not rotate.

　　1. Pre-marital physical examination plays a positive role in preventing birth defects. The extent of its role depends on the items and content of the examination, mainly including serological examination (such as hepatitis B virus, syphilis spirochete, HIV), reproductive system examination (such as screening for cervical inflammation), general physical examination (such as blood pressure, electrocardiogram), and inquiring about the family history of diseases and personal medical history, and doing well in genetic counseling work.

　　2. Pregnant women should try to avoid harmful factors, including staying away from smoke, alcohol, drugs, radiation, pesticides, noise, volatile harmful gases, and toxic heavy metals. During the process of prenatal care in pregnancy, systematic screening for birth defects should be carried out, including regular ultrasound examination, serological screening, and necessary chromosomal examination.

　　1. Upper gastrointestinal contrast study

　　When there is a suspicion of malrotation of the intestine, routine enterography examination should be performed, with barium enema being the first choice, and water-soluble contrast agent can also be selected. After the contrast agent is injected through a nasogastric tube, dynamic observation can be performed under fluoroscopy to obtain more useful information. The most typical manifestation of mesenteric torsion is the 'beak-like' change in the second and third segments of the duodenum; partial obstruction of the duodenum can present as a 'spiral-like' change. It should be pointed out that this examination is not recommended when acute intestinal torsion is suspected.

　　If the child with malrotation has not developed intestinal torsion, upper gastrointestinal contrast examination plays a very important role in determining the position of the duodenojejunal junction (Trendelenburg ligament). Normally, this ligament should be located on the left side of the spine at the level of the gastric antrum, close to the posterior abdominal wall. If there is malrotation, the duodenum has not rotated normally around the SMA, and it is located below the duodenal bulb on the right side of the spine, and closer to the lateral side than the normal position. The expanded intestinal segment filled with fluid that is not visible in the abdominal X-ray can also cause the duodenojejunal junction to move downward, creating a false appearance of malrotation. At this time, contrast medium can be injected through the anus to determine the position of the ileocecal junction.

　　2. Barium Enema

　　Although barium enema is one of the methods for diagnosing malrotation, compared with upper gastrointestinal contrast examination, it has greater limitations, mainly because 15% of normal infants have a free or high position of the ileocecal junction; while the colon of infants is relatively long, which makes it difficult to identify and photograph the ileocecal junction; more importantly, the position of the ileocecal junction in patients with malrotation may be normal.

　　Although there are the above limitations, if the barium enema examination shows that all the colon is located in the left abdomen (seen in complete non-rotation), or (and) the ascending colon is abnormally shortened and the ileocecal junction is located above the iliac wing, malrotation can also be diagnosed.

　　3. Ultrasound

　　As a non-invasive examination, ultrasound helps to diagnose malrotation by investigating the position and direction of the superior mesenteric vessels. Normally, the superior mesenteric vein (SMV) is located on the right side of the SMA. If it is located in front of or on the left side of the SMA, it suggests the possibility of malrotation. However, ultrasound cannot precisely diagnose malrotation. Some authors report that among 9 patients confirmed to have malrotation by surgery, only 6 were found to have abnormal mesenteric vessels by B-ultrasound; in another group of 249 patients who underwent ultrasound examination to exclude pyloric stenosis, only 9 were found to have abnormal mesenteric vessels, among whom 5 cases with SMV located on the left side of the SMA all had malrotation, and the other 4 cases with SMV located on the lateral side of the SMA had only 1 confirmed case of malrotation. This is because the position of the mesenteric vessels in patients with malrotation may be completely normal, and abnormal vessel position cannot determine malrotation. Therefore, ultrasound is not the first choice for diagnosing malrotation, and its role is limited to excluding pyloric stenosis in vomiting children.

　　1. Apple Diet

　　Apples contain tannic acid and have astringent properties. Wash an apple, steam it, and eat the flesh or peel it and mash it into a paste for consumption. Take 30-60 grams each time, three times a day. Apple soup is also an auxiliary beverage for treating diarrhea. Cut the apple into pieces, add 250 milliliters of water and a small amount of salt, and you can also add 5% sugar, boil the soup as tea, suitable for infants under 1 year old.

　　2. Yolk Diet

　　After boiling the eggs, remove the shell and white, and use the yolk to slowly simmer in a pot to extract the oil. For infants under 1 year old, one yolk oil per day, divided into 2-3 doses, for a course of 3 days, to treat diarrhea, and has the effects of benefiting the spleen and stomach to stop diarrhea; The egg yolk mixed with a little flour and ginger slices, steamed into an egg cake, also has the same effect.

　　3. Chestnut Paste

　　Use 3-5 chestnuts, remove the shell, crush them, boil them into a paste, add sugar for seasoning, and eat them twice or three times a day. It has the effect of warming and stopping diarrhea.

　　I. Treatment

　　Children with intestinal torsion and obstruction require emergency surgery, and the first thing to do is to immediately give intravenous fluid replacement, at the same time, place a gastrointestinal decompression tube, Foley catheter, blood cross-matching, and use broad-spectrum antibiotics to control infection. Time is the key to whether the small intestine can be preserved.

　　1. Exploration after entering the abdomen

　　Immediately bring all the intestinal tubes out of the abdominal cavity, explore whether there is intestinal torsion or other causes of intestinal obstruction, and identify the position of the ileocecal junction. When there is intestinal torsion, cloudy ascites in the abdominal cavity suggests the possible existence of bacterial contamination, purulent exudation is seen in ischemic intestinal necrosis; if lymphatic return is blocked, chyle-like ascites appears, and routine ascites culture should be performed.

　　2. Reversal realignment

　　In most cases, intestinal torsion is counterclockwise, and the reversal rotation should be performed, that is, 'turn the clock back'. After realignment, the small intestine may already have congestion, edema, and local necrosis. At this time, warm water can be applied for a while to observe the blood supply of the intestinal tract. If intestinal necrosis already exists, intestinal resection and fistula should be performed. To retain as much small intestine as possible, some temporarily undetermined suspicious intestinal segments should be left alone for observation for 24-36 hours, and reoperation should be decided whether to resect or not.

　　3. Ligament loosening

　　The ligament can compress the duodenum and cause repeated obstructions, which must be loosened, usually loosened to the portal above the duodenum and below the duodenal jejunum connection.

　　4. Widen the mesentery base

　　Loosening the ligament on the inner side of the duodenum can further increase the distance between the duodenum and the ascending colon, maximize the expansion of the mesentery base, and reduce the opportunity for intestinal torsion. However, it does not emphasize the复位 of the ileocecal junction and duodenum to the normal anatomical position.

　　5. Relief of duodenal obstruction

　　The duodenal adhesion site can form a 'spiral-like' structure.

　　II. Prognosis

　　The mortality rate for surgical treatment of intestinal malrotation is 3% to 9%, and if it is accompanied by small bowel necrosis, preterm birth, and other malformations, the mortality rate increases. With the increasingly perfect intensive care and enteral and parenteral nutrition support methods, the survival rate of the disease has greatly improved. In addition, timely identification of the symptoms of intestinal torsion and malrotation, early diagnosis and treatment are important links to improve the prognosis.