Annular pancreas

　　Currently, there are mainly two explanations for the pathogenesis of annular pancreas. The pancreas is gradually developed and fused from several protrusions on the embryonic primitive gut wall. The dorsal pancreatic primordium arises directly from the duodenal wall, while the ventral pancreatic primordium originates from the root of the liver protuberance. Subsequently, the dorsal pancreatic primordium develops into the body and tail of the pancreas, with its stalk becoming the accessory pancreatic duct. The ventral pancreatic primordium's stalk becomes the main pancreatic duct, and the end becomes the pancreatic head.

　　Around the 6th week of embryogenesis, with the transposition of the duodenum, the ventral pancreas also transposes to the posterior and inferior part of the dorsal pancreas. By the 7th week, the dorsal and ventral pancreases begin to contact, and finally the two pancreases merge into one, with the two pancreatic ducts also merging and贯通.

　　Therefore, one theory suggests that annular pancreas is caused by the failure of the ventral duodenal primordium to fuse with the dorsal primordium due to its inability to rotate with the duodenum. Another theory proposes that due to the simultaneous hypertrophy of the ventral and dorsal pancreatic primordia, annular pancreas is formed, completely or partially surrounding the second segment of the duodenum, causing obstruction.

　　The three main complications of annular pancreas are peptic ulcer, gallstones, and pancreatitis.

　　1, Peptic ulcer:Annular pancreas often occurs with gastric and duodenal ulcers, with duodenal ulcers being more common, often occurring behind the bulb, and sometimes the ulcer is exactly located at the duodenum surrounded by the annular pancreas. The cause of ulcers is related to the high acidity of the gastric and duodenal contents and the damage to the gastrointestinal mucosa caused by the retention of contents.

　　2, Gallstones and obstructive jaundice:Due to the location of annular pancreas at the ampulla of Vater, or due to the significant narrowing of the descending duodenum caused by annular pancreas, the upper segment is obviously dilated, compressing the common bile duct. It can also be due to reasons such as obstruction of the lower end of the common bile duct caused by pancreatitis, resulting in poor bile excretion and easy formation of gallstones. Gallstones can cause jaundice, and compression of the common bile duct or concurrent pancreatitis can cause obstructive jaundice.

　　3, Pancreatitis:Pancreatitis is often the main cause of the symptoms of annular pancreas and becomes the reason for patients to seek medical attention. The edema of acute pancreatitis or the scar fibrosis of chronic pancreatitis and adhesion to adjacent organs can aggravate duodenal obstruction. Pancreatitis can be limited to part of the annular pancreas or involve the whole pancreas. The cause of pancreatitis may be related to the abnormal opening of the pancreatic duct of annular pancreas, or due to compression of the lower end of the common bile duct, causing bile to flow back into the pancreatic duct and activating pancreatic enzymes.

　　In addition to the above three diseases, annular pancreas can also cause the following diseases: tongue sticking idiocy, esophageal atresia, esophageal tracheal fistula, Meckel diverticulum, congenital heart disease, deformed feet, peptic ulcer, acute pancreatitis, biliary obstruction, and so on.

　　The clinical symptoms of annular pancreas are different for patients of different ages.

　　1, Infant type:The neonatal type usually occurs within one week after birth, and it is rare to occur more than two weeks after birth. The main manifestation is acute complete obstruction of the duodenum. The child shows refractory vomiting, with the vomit containing bile. Due to frequent vomiting, dehydration, electrolyte imbalance, acid-base imbalance, and malnutrition may occur. If it is incomplete obstruction of the duodenum, it is manifested as intermittent abdominal pain and vomiting, which may be accompanied by discomfort in the upper abdomen after eating. These symptoms may occur repeatedly. In addition, annular pancreas often occurs with other congenital diseases, such as tongue sticking idiocy, esophageal atresia, esophageal tracheal fistula, Meckel diverticulum, congenital heart disease, deformed feet, and so on.

　　2, Adult type:The adult type is more common in people aged 20 to 40, and the symptoms are mainly chronic incomplete obstruction of the duodenum. The earlier the symptoms appear, the more severe the obstruction of the duodenum becomes. The main symptoms include recurrent upper abdominal pain and vomiting, which occur in paroxysmal attacks, worsen after eating, and are accompanied by vomiting, with the vomit containing gastric and duodenal fluids and bile.

　　Annular pancreas cannot be prevented by artificial efforts after birth and it belongs to congenital diseases. The responsibility for preventing this disease mainly lies with pregnant women, who should pay special attention to hygiene and dietary habits during pregnancy, develop good living habits, quit smoking and drinking, and do well in these aspects. In addition, the living environment of infants must be kept away from electromagnetic radiation, and nutrition needs to be sufficient during the neonatal period.

　　Later, for patients with biliary obstruction, in addition to relieving duodenal obstruction, it is also necessary to relieve biliary obstruction. Gastric subtotal resection, Billoth-Ⅱ anastomosis, and side-to-side anastomosis between the common bile duct and the distal end of the duodenal obstruction can be performed. For patients with annular pancreas complicated with gastric and duodenal obstruction, partial gastrectomy, Billoth-Ⅱ anastomosis can be performed, and vagotomy can be added if necessary.

　　Annular pancreas is a congenital developmental malformation, with a band-like pancreatic tissue ring that partially or completely encircles the first or second segment of the duodenum, causing intestinal lumen stenosis.

　　1. X-ray examination:The abdominal X-ray mainly shows duodenal obstruction. In the supine position, the stomach and duodenal bulb are dilated and distended, known as the double bubble sign. If there is a large amount of retained fluid in the stomach and duodenal bulb, a liquid level can be seen in the stomach and duodenal bulb in the upright position.

　　2. Endoscopy:Under normal mucosal endoscopy, there is little help to the diagnosis, and in severe cases, the descending part of the duodenum can be seen as a ring-like stenosis under endoscopy. It can be accompanied by duodenal ulcer.

　　3. Gastrointestinal barium enema:Manifested as gastric dilatation, prolapse, with a large amount of fasting retained fluid in the stomach, prolonged emptying time, the duodenal bulb is uniformly expanded and elongated, and the inferior margin is smooth and rounded. The duodenal bulge, occasionally there is a well-defined localized narrowing area in the first or third segment, and the mucosal folds in this area are sparse, and there is visible retrograde peristalsis in the bowel above the narrowing.

　　For annular pancreas patients in the infantile period, if the intestinal peristalsis recovers, breast milk should be given in small amounts, and try to eat more frequent, smaller meals to prevent anastomotic fistula due to overeating. After eating, attention should be paid to the amount and color of feces. Research shows that charcoal-grilled foods can increase the probability of annular pancreas. Therefore, in daily life, it is necessary to pay attention to moderate intake of processed meats, pork, and red meats such as sausages and grilled foods.

　　For annular pancreas without symptoms or with不明显 symptoms, surgery may not be necessary. If it has caused duodenal stenosis or obstruction, surgical treatment is necessary.

　　1. Duodenoduodenal side-to-side anastomosis:This operation is relatively easy, capable of completely relieving duodenal obstruction, while maintaining the function of the stomach, and without damaging the pancreatic duct, thus reducing the risk of pancreatic fistula. Therefore, it is more in line with physiology and can be used as the first choice of operation. The surgical method involves incising the retroperitoneum on the lateral margin of the duodenum, freeing the proximal and distal parts of the obstructed duodenum; then, two牵引 lines are made on the anterior wall of the bowel at the proximal and distal ends of the obstruction. Subsequently, a transverse incision is made on the anterior wall of the proximal bowel, and a longitudinal incision on the distal anterior wall. The incision is sutured with 1号线 in an interrupted full-thickness manner, and finally, the seromuscular layer is sutured in an interrupted manner.

　　2. Duodenal Jejunum Roux-y Anastomosis:This procedure has the advantages of the duodenal and duodenal side-to-side anastomosis, but attention should be paid to the following points during the surgical process of the annular pancreas. The anastomosis should be selected at the lowest point near the duodenal obstruction to avoid the formation of a blind loop. The anastomosis should not be too small to avoid the formation of a stricture. Do not twist the jejunum into an angle during anastomosis to avoid obstruction. The jejunum is cut 15-20 cm away from the Treitz ligament, and the distal end is anastomosed to the lowest point near the duodenal obstruction.

　　3. Duodenal Jejunum Side-to-Side Anastomosis:The advantages of this procedure are also the same as those of the duodenal side-to-side anastomosis. The method is to anastomose a segment of jejunum 15-20 cm away from the Treitz ligament to the proximal duodenum of the obstruction, in front of or behind the transverse colon, in a side-to-side manner. The precautions during surgery are basically the same as those for the duodenal jejunum Poux-y anastomosis.

　　4. Gastrojejunostomy:This procedure has two prominent characteristics. There may be marginal ulceration at the anastomosis after surgery, the duodenal drainage near the obstruction is not good, and it cannot well relieve the duodenal obstruction. Therefore, except for the fact that there is tight adhesion around the duodenum, which prevents the implementation of other bypass surgeries, this procedure is generally not suitable. The most ideal method for adult cases is to perform a partial gastrectomy first and then perform a gastrojejunostomy.

　　5. Annular Pancreatectomy:If the annular pancreas tissue is thin and the blood vessel distribution is not much, and it is not tightly adhered to the intestinal wall, the annular pancreas can be cut off, or partially or completely removed, to relieve duodenal obstruction. If the duodenum has become narrow due to long-term compression, a longitudinal incision and transverse suture can be added to the duodenal duodenum to enlarge the intestinal lumen. However, this therapy can cause complications such as pancreatic injury, pancreatic fistula, pancreatic cyst, or duodenal fistula; sometimes after surgery, the narrowing or obstruction of the duodenal duodenum cannot be completely relieved. Therefore, this western medicine surgical therapy is not used much.