Annular pancreas

　　There are many theories about the etiology of annular pancreas. Annular pancreas is one of the causes of congenital duodenal obstruction in children. It is a malformation of the pancreas where the tissue develops abnormally into a ring or clip shape, encircling the descending part of the duodenum. When the annular pancreas exerts pressure on the intestine, it can cause complete or incomplete obstruction of the duodenum. When there is a developmental disorder, or if part of the ventral pancreas is adhered to the intestine, it can become an ectopic pancreas. If the ventral pancreas does not rotate left with the duodenum and fuse with the dorsal pancreas, a strip of pancreatic tissue will encircle the duodenum, partially or completely encircling the first or second segment of the duodenum, narrowing the lumen, forming an annular pancreas.

　　Annular pancreas can be accompanied by conditions such as glossoptosis, esophageal atresia, esophageal tracheal fistula, Meckel diverticulum, congenital heart disease, malformed feet, peptic ulcer, acute pancreatitis, biliary obstruction, and more.

　　Ring pancreas is clinically divided into neonatal and adult types, and its clinical manifestations are closely related to the degree of compression of the duodenum and other associated pathological changes.

　　1. Neonatal-type usually occurs within one week after birth, and cases occurring more than two weeks are rare. The main manifestation is acute complete duodenal obstruction. The infant exhibits intractable vomiting, with the vomit containing bile. Due to frequent vomiting, dehydration, electrolyte imbalance, acid-base imbalance, and malnutrition can occur. If it is incomplete duodenal obstruction, it manifests as intermittent abdominal pain and vomiting, which can be accompanied by discomfort in the upper abdomen, and it worsens after eating. These symptoms can occur repeatedly. In addition, ring pancreas often accompanies other congenital diseases, such as tongue-like mental retardation, esophageal atresia, esophageal tracheal fistula, Meckel's diverticulum, congenital heart disease, deformed feet, etc.

　　2. Adult-type is more common in people aged 20 to 40, and mostly presents with symptoms of chronic incomplete duodenal obstruction. The symptoms appear earlier, and the manifestation of duodenal obstruction is more severe. The main symptoms include recurrent upper abdominal pain and vomiting, which are paroxysmal in nature. Abdominal pain worsens after eating, and vomiting can alleviate it. The vomit contains gastric and duodenal fluid, containing bile. In addition to duodenal obstruction, patients can also have other pathological changes and cause corresponding clinical symptoms.

　　The occurrence of ring pancreas is a congenital developmental anomaly, therefore, during pregnancy, mothers should perform checks to reduce the birth of such children. Early detection, early diagnosis, and early treatment are also the key to preventing the disease.

　　The examination of ring pancreas includes laboratory examination and other auxiliary examinations, and the specific examination methods are described as follows.

　　Firstly, laboratory examination

　　Meconium examination:Perform staining and microscopic examination with the middle part of meconium. If squamous epithelial cells or fetal hair ingested with amniotic fluid can be found, it can be inferred that the intestinal tract was patent for a period of time during fetal development. If there is a ring pancreas causing complete obstruction, such cells cannot be found in the meconium.

　　Secondly, other auxiliary examinations

　　1. Abdominal plain film:The main manifestation is duodenal obstruction. In the supine position, the stomach and duodenal ampulla are dilated and distended, showing the so-called double bubble sign. Due to the large amount of fasting retained fluid in the stomach and duodenal ampulla, a liquid level can be seen in the stomach and duodenal ampulla in the standing position. Sometimes, both the upper and lower parts of the duodenal narrowing area are distended, thus highlighting the shadowing of the narrowing area.

　　2. Gastrointestinal barium enema:Manifested as gastric dilatation and prolapse, with a large amount of fasting retained fluid inside, and an extended emptying time. The duodenal ampulla is symmetrical in expansion and elongation, with a smooth and rounded lower margin. Occasionally, the descending segment of the duodenum may have a well-defined localized narrowing area in the first or third segment, with sparse mucosal folds and a longitudinal arrangement, and it can be eccentric or concentric. The above the narrowing, the intestinal tract can be seen to exhibit retrograde peristalsis, and the presence of ulcers can be detected.

　　3. Endoscopic Retrograde Cholangiopancreatography (ERCP):Subendooscopic contrast can make the annular pancreatic duct visible, which is very helpful for diagnosis. Since the duodenal stenosis caused by annular pancreas often occurs near the main papilla, if the endoscope cannot pass through the stenosis, it is impossible to造影. Sometimes, a stenosis of the common bile duct can occur due to compression by the annular pancreas at the end of the common bile duct.

　　4. CT:After taking the contrast agent, the duodenum is filled, and the pancreatic tissue surrounding the descending part of the duodenum connected to the head of the pancreas is usually not directly visible due to the thin annular pancreas tissue. If there are indirect signs such as swelling of the pancreatic head and thickening and narrowing of the descending part of the duodenum, they are also helpful for diagnosis.

　　5. Magnetic Resonance Imaging (MRI) and Magnetic Resonance Cholangiopancreatography (MRCP):MRI can show tissue structures with the same signal intensity as the pancreas surrounding the descending part of the duodenum connected to the head of the pancreas, which can be confirmed as pancreatic tissue. MRCP can well display the annular pancreatic duct shadow through the principle of water imaging. MRCP is non-invasive, without radiation, and patients have no pain, making it simple and convenient.

　　6. Endoscopy:In most cases, normal mucosa under endoscopy is not helpful for diagnosis. In severe cases, the descending part of the duodenum can be seen as annular stenosis under endoscopy, and duodenal ulcer can occur simultaneously.

　　Patients with annular pancreas should eat foods rich in vitamin C and amino acids; avoid eating high-fat and acidic foods. The specific dietary precautions are described as follows.

　　1. During the non-acute phase, it is advisable to eat foods that have no mechanical and chemical stimulation to the gastrointestinal tract, and to eat high-carbohydrate and low-fat liquid foods. The protein supply should be 60 grams per day, including an appropriate amount of high-quality protein. The intake of fat should be strictly limited (gradually transitioning from 20 grams per day to 40 grams per day). It is advisable to choose easily digestible carbohydrates (such as brown sugar, sucrose, honey, etc.), as carbohydrates are the main source of energy, and can be given more than 300 grams per day. The diet should be light, and cooking methods with less oil, such as steaming, boiling, braising, stewing, and blanching, should be chosen. It is advisable to eat less and more often, 4-5 times per day.

　　2. Avoid foods that are easy to cause bloating (such as radishes, onions, coarse grains, dried beans, etc.). Avoid刺激性 foods. Abstain from strong tea, coffee, alcohol, animal internal organs, fatty ducks, etc. Avoid overeating and overdrinking. Avoid greasy, fried, and fried foods. Pay special attention to abstain from alcohol.

　　If there are no symptoms or the symptoms are not obvious in patients with annular pancreas, surgery is not necessary. If duodenal stenosis or obstruction has occurred, surgical treatment must be performed. The methods of surgical treatment are described as follows.

　　1. Annular Pancreas Resection

　　If the annular pancreas tissue is thin, with few blood vessels distributed and no close adhesion to the intestinal wall, the annular pancreas can be cut off, or partially or completely resected, to relieve duodenal obstruction. If the duodenum has become narrowed due to long-term compression, additional longitudinal incision and transverse suture of the duodenum can be performed to enlarge the intestinal lumen. The disadvantages of this surgical method are that it can cause complications such as pancreatic injury, pancreatic fistula, pancreatic cyst, or duodenal fistula, and sometimes the narrowing or obstruction of the duodenum after surgery cannot be completely relieved. Therefore, it is not recommended to adopt this method.

　　Second, bypass surgery

　　1. Duodenal and side-to-side duodenal anastomosis:This surgical method is relatively easy to perform, can completely relieve the duodenal obstruction, maintain the function of the stomach, and has no risk of pancreatic duct injury or pancreatic fistula, so it is more in line with physiology and can be chosen as the first-line method.

　　2. Duodenal jejunal Roux-y anastomosis (anteroposterior or posterior to the colon):This surgical method has the advantages of both the duodenal and side-to-side duodenal anastomosis. However, the following points should be noted during the surgical process.

　　(1) The anastomosis should be performed at the lowest point of the proximal duodenal obstruction to avoid the formation of a blind loop.

　　(2) The anastomosis should not be too small to avoid narrowing.

　　(3) Do not twist the jejunum into an angle during anastomosis to avoid obstruction.

　　(4) The jejunum is cut 15-20 cm from the Treitz ligament, and the distal end is anastomosed to the lowest point of the proximal duodenal obstruction.

　　3. Side-to-side duodenal jejunal anastomosis:The advantages of this surgical method are also the same as those of the side-to-side duodenal anastomosis. The precautions during surgery are basically the same as those of the duodenal jejunal Poux-y anastomosis.

　　4. Gastrojejunal Anastomosis:This surgical method has the following two outstanding characteristics.

　　(1) Ulceration at the anastomotic margin may occur after surgery.

　　(2) The duodenal drainage at the proximal obstruction is poor, and it cannot effectively relieve the duodenal obstruction.

　　Therefore, except for the case where there is tight adhesion around the duodenum, making it impossible to perform other bypass surgeries, this surgical method is generally not recommended. Performing subtotal gastrectomy followed by a gastrojejunal anastomosis is the most ideal method in adult cases.

　　In addition, for patients with biliary obstruction, in addition to relieving the obstruction of the duodenum, the obstruction of the bile duct also needs to be relieved. Laparoscopic subtotal gastrectomy, Billoth-Ⅱ anastomosis, and side-to-side anastomosis between the common bile duct and the distal end of the duodenum obstruction can be performed. For patients with annular pancreas complicated with gastric and duodenal obstruction, subtotal gastrectomy, Billoth-Ⅱ anastomosis, and vagotomy may be necessary.