Neonatal digestive tract duplication

　　1. Etiology

　　It is an anomaly in embryonic development, but there are many factors contributing to the formation of the anomaly, and it is considered to be polygenic.

　　1. Abnormal cavitation process of the intestinal tube during the embryonic period

　　Starting from the fifth week of embryonic development, the intestinal tubes begin to fill, become vesicular, and undergo cavitation. During cavitation, if a vesicle does not communicate with the intestinal tube, it can form an intestinal cystic type of digestive tract duplication, which can occur from the small intestine to the colon.

　　2. Development of diverticulum-like external pouches

　　During the embryonic period, the midgut often forms many temporary diverticula, which become external pouches and then regress and disappear. If some do not regress or become isolated, they become tubular or isolated cystic intestinal duplications communicating with the intestine.

　　3. The theory of notochord splitting

　　During the third week of embryonic development, the notochord grows towards the cranial end between the ectoderm and endoderm. If local adhesion occurs between the ectoderm and endoderm, the notochord will split into two branches at the site of adhesion, bypassing the adhesion from both sides, and then remerge to continue growing towards the cranial end. The ectoderm forms the neural tube, and the notochord is surrounded by the mesoderm to form the spine. The adhesion between the ectoderm and endoderm pulls the intestinal wall to form diverticula, and the adhesion also obstructs the formation of vertebral bodies from the notochord, leading to vertebral clefts. Therefore, one-third of patients with this condition have associated spinal deformities. If the diverticulum neck closes, it can form a cystic intestinal duplication anomaly.

　　4. Caudal twin anomaly

　　In a few cases, there are long tubular duplications parallel to the entire colon and rectum, often accompanied by reproductive and urinary system duplications, such as double uterus, double vagina, double bladder, double urethra, and double external genitalia.

　　5. Poor separation of the tracheo-esophageal groove from the foregut

　　The fourth week of embryonic development sees the appearance of the tracheo-esophageal groove, which gradually closes to separate into a tube from the esophagus. If part of it fails to close, it can form a fistula between the foregut and respiratory tract. This fistula, if partially regressed during the embryonic period, can lead to esophageal duplication anomalies.

　　2. Pathogenesis

　　Repeated malformations can occur in any part of the digestive tract, with the ileum being the most common, accounting for about 50%, followed by the jejunum, cecum, and esophagus. The stomach, duodenum, and colon rarely occur. Those located in the thoracic cavity account for about 21.5%.

　　Repeated malformations can be divided into 4 types:

　　1. Extra-intestinal Cystic Type

　　It is more common, presenting as spherical or elliptical, located in the mesentery adjacent to the intestinal tract. Most of them are closely adherent to the adjacent intestinal wall with a common wall layer. Most of them are not connected to the intestinal lumen, and only a few have holes connected. The surface of the cyst is smooth, covered with serosa, and the cyst cavity contains colorless or slightly yellow mucus, making the entire cyst have tension and elasticity.

　　2. Intestinal Cystic Type

　　Cysts are located in the submucosal layer or muscular layer of the intestinal wall, which can cause obstruction of the intestinal lumen.

　　3. Tubular or Bifid Intestinal Tract

　　There is another tubular intestinal tract parallel to the normal intestinal tract in the mesentery, presenting as a double-barrel intestinal tract. The length varies, from a few centimeters to 50 cm. Generally, the distal and proximal ends of the lumen are often connected to the digestive tract, sometimes only one end is connected, similar to a diverticulum. The small intestine usually opens at the distal end, while the colon usually opens at the proximal end.

　　4. Intrathoracic Gastrointestinal Duplication Malformation

　　Cysts are often near the esophagus or tracheobronchial tube, and can have cords connected to the vertebrae, accompanied by vertebral cleft or spinal malformation. The tubular type can pass through the diaphragm into the mesentery and be close to the digestive tract.

　　The tubular wall of the repeated digestive tract has a muscular layer and mucosa, with properties similar to adjacent digestive tracts, but not necessarily the same at the same level. About 20% is atypical digestive tract mucosa. If it is gastric mucosa or pancreatic tissue, it can cause peptic ulcer, resulting in hemorrhage and perforation, which is often attached to a certain part of the digestive tract, with a common blood supply source.

　　It can complicate with intestinal obstruction, ulcer, and can complicate with intestinal hemorrhage, hematemesis, or hemoptysis, which can lead to anemia. It can complicate with intestinal necrosis and peritonitis. It can coexist with intestinal or anal atresia, malrotation of the intestines, Meckel's diverticulum, anal atresia, and umbilical hernia, etc. It can also coexist with bicornuate uterus, double vagina, double bladder, double urethra, and even double external genitalia. It often accompanies spinal bifida, meningocele, and other malformations.

　　1. Gastrointestinal Obstruction

　　The incidence of repeated malformations in the ileum, ileocecal junction, and hollow viscera is high, hence the symptoms of small bowel obstruction are the most common. Both cystic and tubular malformations can compress the intestinal lumen, which is the main cause of obstruction. Cystic malformations can secrete a large amount of fluid due to the mucosa, increasing intraluminal pressure, causing the cyst to swell and obstruct. Tubular malformations, like those near the proximal end, are connected to the intestinal lumen, while the distal end is blind. Due to the accumulation and expansion of intestinal contents, partial intestinal obstruction can occur, manifested as repeated vomiting and abdominal distension. Repeated malformations at the ileocecal junction can sometimes be palpated in the lower right abdomen. Larger cysts in the mesentery can cause torsion, and can also lead to绞窄性肠梗阻 due to intestinal torsion. Cysts within the ileocecal wall can cause intussusception. Cystic malformations in the stomach and duodenum are usually small, but can cause pyloric or duodenal obstruction in neonates. A cystic mass can be palpated in the upper left abdomen, accompanied by vomiting, which may result in hematemesis or melena.

　　2. Gastrointestinal bleeding

　　Tubular repeated malformations that open into the normal intestinal lumen may frequently secondary to peptic ulcers, bleeding, even perforation, recurrent vomiting of blood and hematochezia, leading to anemia.

　　3. Gastrointestinal duplication malformation located in the thoracic cavity

　　It can cause symptoms of organ compression, esophageal compression can lead to dysphagia, respiratory compression can cause cough, asthma, cyanosis, and other symptoms. In the neonatal period, respiratory distress may occur, such as if it affects the excretion of respiratory secretions, recurrent respiratory infections may occur. Cystic malformations, if there is gastric mucosa, can cause ulcers,溃烂 towards the esophagus or trachea, leading to hemoptysis or vomiting of blood.

　　Good genetic counseling should be done, good prenatal care should be taken, and active prevention and treatment of various infectious diseases should be carried out. The preventive measures refer to other birth defect diseases. To reduce and reverse the incidence rate of neonatal birth defects, prevention should start from pre-pregnancy to prenatal: how to prevent neonatal gastrointestinal duplication syndrome?

　　1. Pre-marital physical examination plays a positive role in preventing birth defects, the extent of which depends on the items and content of the examination, mainly including serological tests (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 family history of diseases and personal medical history, etc., to do a good job in genetic counseling.

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

　　Once abnormal results appear, it is necessary to clarify whether to terminate the pregnancy; the safety of the fetus in the uterus; whether there are sequelae after birth, whether it can be treated, and what the prognosis is, etc. Take practical and feasible diagnostic and treatment measures.

　　1. X-ray examination

　　Abdominal upright film can be used to understand the presence of intestinal obstruction and peritonitis. In chronic cases, barium enema can be applied. Chest X-ray can detect repeated malformations within the thoracic cavity, which are manifested as clear marginal round shadows, or it may be observed that the heart, lungs, and mediastinum are shifted to the opposite side, which can serve as a reference for diagnosis. Thoracic X-ray film can also understand the presence of spina bifida, hemivertebrae, and scoliosis, etc., which are helpful for diagnosis.

　　2. Ultrasound examination

　　It can differentiate the nature of abdominal masses, whether they are cystic or solid, and cystic masses are helpful in the diagnosis of intestinal duplication malformations.

　　3. Radioisotope examination

　　The application of 99mTc abdominal scanning helps in the diagnosis of gastrointestinal duplication malformations containing gastric mucosal tissue, but it is not easy to differentiate from Meckel's diverticulum.

　　4. CT examination

　　It can show whether the chest or intestinal cavity mass is cystic or solid, which indirectly helps in the differential diagnosis of gastrointestinal duplication malformations.

　　1. Avoid alcohol, tobacco, strong tea, and coffee: Regular drinking of strong alcohol has a significant stimulating effect on the gastric mucosa, and patients with upper gastrointestinal bleeding should abstain from drinking. Long-term alcoholism also causes significant damage to the liver, affects the synthesis of coagulation factors, and is prone to trigger upper gastrointestinal bleeding.

　　The harmful components in tobacco leaves have a significant irritating effect on the gastrointestinal mucosa, which is easy to cause inflammation of the gastrointestinal mucosa, disrupt the function of the lower esophageal sphincter and the lower esophageal sphincter, and lead to the reflux of bile and gastric contents, exacerbating the condition. For patients with a history of upper gastrointestinal bleeding, it is particularly important to quit smoking. Strong tea and strong coffee can strongly stimulate the secretion of gastric acid, which is not conducive to the regression of gastrointestinal inflammation and the healing of the ulcer surface, so patients with a history of gastrointestinal bleeding should not drink strong tea and coffee.

　　2. Avoid spicy and刺激性 food: Spicy, aromatic, fried foods, etc., are hot and easy to ignite. In addition, seafood is more刺激性，which can damage the gastrointestinal mucosa and cause bleeding.

　　1. Treatment

　　This disease often causes serious complications, such as once found, surgical treatment should be performed immediately. Repeated malformations often have a common muscular layer and the same blood supply source as the gastrointestinal tract, making them difficult to separate. Generally, it is necessary to excise the malformation and the local gastric or intestinal wall, and then perform anastomosis. Mesenteric cysts are not connected with the gastrointestinal tract and can be treated with simple cystectomy. Thoracic cavities are often solitary cysts, and excision surgery can be performed. If the esophagus, trachea, or bronchus is pierced, the affected tissue must be excised along with it, and then repaired. Thoracic tubular malformations enter the abdominal cavity through the diaphragm and are removed in stages through surgery.

　　2. Prognosis

　　Patients who undergo surgery before the onset of various complications have a good prognosis, while those who start surgery after the onset have a poor prognosis and certain risks.