Small intestinal duplication malformation

　　1. Causes of Disease

　　There are many theories about the etiology of small intestinal duplication malformations, but each theory cannot fully solve the cause of the occurrence of duplicated malformations at various locations. The etiology may be polygenic, and the etiology of different locations and different pathological changes may be different.

　　1. The theory of primary intestinal cavitation disorder suggests that after the 5th week of embryonic development, the rapid proliferation of epithelial cells in the primary intestinal cavity causes the intestinal cavity to appear temporarily occluded. Later, the occluded intestinal cavity epithelial cells appear many vesicles, making the occluded intestinal cavity相通 again, which is the cavitation period. If there is a developmental disorder at this time, the intestinal cavity between the intestines may appear parallel to the digestive tract, which may form an intestinal cystic type of duplicated malformation.

　　2. The theory of diverticulum-like outer pouch suggests that at 8-9 weeks of embryonic development, the distal part of the small intestine forms a temporary diverticulum-like outer pouch due to the outward proliferation of epithelial cells covered by connective tissue. This pouch gradually disappears later. If it remains, the diverticulum-like outer pouch at the original site can develop into a cystic type of small intestinal duplication malformation.

　　3. The theory of neural tube-primary intestine separation disorder suggests that at 3 weeks of embryonic development, the notochord forms between the inner and outer germ layers. If there is abnormal adhesion between the inner and outer germ layers at this time, the notochord is divided into two parts, left and right, at this location. The notochord and vertebral body form a cord-like neural gut between the outer germ layer and the digestive tract. When the endoderm develops into the intestine later, the part of the intestine pulled by the cord-like adhesion bulges out to form a diverticulum-like protuberance, which can develop into duplicated malformations later. Since the adhesions all occur on the dorsal side of the primary intestine, the duplicated malformations are also located on the mesenteric side. The cord-like adhesions can affect the development of the vertebral body, so this type of duplicated malformation often accompanies vertebral body developmental malformations, such as hemivertebrae and butterfly vertebrae. Li Long et al. classified intestinal duplication malformations into two types, and the mesenteric type of duplicated malformation is exactly located between the two mesenteries, accounting for 91.6%. It is proposed that this type is caused by the separation disorder between the notochord and the primary intestine.

　　4. The theory of primary intestinal ischemic necrosis suggests that after the completion of primary intestinal development, due to ischemic necrotic lesions in the primary intestine, changes such as intestinal atresia, stenosis, and short small intestine may occur. The fragments of the intestine left after necrosis receive blood supply from nearby vessels and can develop into duplicated malformations on their own. Therefore, some children with small intestinal duplication malformations may also have malformations such as intestinal atresia, stenosis, and short small intestine.

　　II. Pathogenesis

　　Small intestinal duplicated malformations have a normal digestive tract tissue structure. Most malformations fuse with the main intestinal tube to form a common muscle wall, sharing common serosa, mesentery, and blood supply, but having an independent, separated, or communicating mucosal cavity. A few malformations have a separate mesentery and blood vessels. The mucosa within the cavity of small intestinal duplicated malformations is mostly lined with the mucosa of the main intestinal tube, with 20% to 35% being ectopic gastrointestinal mucosa or respiratory mucosa. The ectopic mucosa most commonly includes gastric mucosa, occasionally with two or more types of ectopic mucosa. 80% of duplicated malformation mucosal cavities do not communicate with the main intestinal tube, accumulating mucosal secretion fluid within the cavity, forming round or oval cysts. Malformations are mostly solitary, and in a few cases, more than two duplicated malformations can coexist in the gastrointestinal tract. Duplicated malformations are benign diseases in children, but they can undergo malignant transformation in adulthood. The pathological morphology of small intestinal duplicated malformations can take various forms.

　　1. Classification according to clinical appearance

　　(1) Extraintestinal cystic type of duplicated malformation: This is the most common type of duplicated malformation. It manifests as round or oval cystic masses that do not communicate with the small intestinal lumen, closely attached between the two leaves of the small intestinal mesentery. The size of the cysts varies greatly, with the smaller ones only 1 cm in diameter and the larger ones occupying a large part of the abdominal cavity. The cysts are filled with colorless or pale yellow mucosal secretion fluid. Once the cysts grow to a certain extent, they can compress the main intestinal tube or trigger intussusception. Cysts with a lining of ectopic gastric mucosa or pancreatic tissue can be eroded by gastric acid or pancreatic enzymes, causing peptic ulcers within the cyst lumen, leading to bleeding or perforation in the cyst cavity, resulting in peritonitis.

　　(2) Intramural cystic type of duplicated malformation: Cysts occur in the muscular layer of the jejunum or ileum or submucosa, and do not communicate with the intestinal lumen of the small intestine. This type is more common in the distal ileum or ileocecal region. Zhao Li et al. reported 13 cases of intramural cystic malformation, 11 cases (84.6%) located in the distal ileum within 5 cm of the ileocecal valve. This type of cyst protrudes into the intestinal lumen as it slightly increases in size, causing obstruction or triggering intussusception early on, and the diameter of the cyst rarely exceeds 4 cm.

　　(3) Tubular type of duplicated malformation: There are two morphological types of tubular type duplicated malformation.

　　①Long tubular malformation: The malformation is tubular in shape, attached to the mesenteric side and runs parallel to the main intestinal tube. The wall of the malformation has a completely normal intestinal tract structure and often shares the mesentery and blood supply with the main intestinal tube. The length of the malformation varies, with the smaller ones several centimeters long and the larger ones extending up to 50-70 cm, even involving the entire small intestine. Most malformations have a blind end at the proximal end of the intestinal tube, opening into the main intestinal tube; the inner lining is gastric mucosa or pancreatic tissue, more common than the cystic type, and the malformation does not communicate with the main intestinal tube; or the distal end is blind-ended, and the proximal end opens into the main intestinal tube, with a large tubular cyst filled with a large amount of mucosal secretion fluid in the malformation cavity, which can displace or compress the main intestinal tube, causing intestinal obstruction.

　　②Diverticuliform malformation: The malformation presents as diverticula, extending from the mesentery within the main intestinal tube to any part of the abdominal cavity. The terminal end is in a free state, adhering to the intestinal tract or organ it contacts; the proximal segment of the intestinal tube varies in length and opens into the main intestinal tube.

　　(4) Chest and abdominal duplication anomalies: Chest and abdominal duplication anomalies account for 2% to 6% of gastrointestinal duplication anomalies, and can originate from any part of the gastrointestinal tract in the abdomen. Chest and abdominal duplication anomalies of the small intestine often originate from the jejunum, with the anomaly presenting as a long tubular structure extending from the mesenteric side of the main intestinal tube, passing through a certain abnormal diaphragmatic or esophageal hiatus into the posterior mediastinum behind the peritoneum. The terminal part of the anomaly can extend to the top of the pleura and attach to the cervical vertebra or upper thoracic vertebra. Chest and abdominal duplication anomalies are often accompanied by spinal anomalies, such as hemivertebrae, vertebral fusion, anterior spina bifida, or intraspinal neural tube cysts.

　　(5) Chest and abdominal duplication anomalies can also exist separately in the chest and abdomen, with no connection between them. Such cases are rare, and it is easy to misdiagnose or miss the diagnosis clinically. Therefore, after the diagnosis of duplication anomalies in any location, a careful examination should be conducted to determine whether there is a second anomaly.

　　2. Classification by mesenteric blood supply relationship: In recent years, Li Long and others have classified small intestinal duplication anomalies according to the relationship between the blood supply of the intestinal tube and the main intestinal tube mesentery, and divided them into conjoined type and mesenteric type.

　　(1) Conjoined type (Type I): The aorta separates from the marginal artery in the mesenteric margin to emit blood to both intestinal tubes, with each blood vessel from both sides of the peritoneum to the supplied intestinal tube. The blood vessels supplying the main intestinal tube do not pass through the duplicated intestinal tube, and the interruption of the blood supply of the duplicated intestinal tube does not affect the blood supply of the main intestinal tube. This type accounts for 75.3% of duplication anomalies, with cystic type being the most common, and the incidence of thoracic vertebral anomalies is only 6.2%.

　　(2) Mesenteric type (II): The duplicated intestinal tube is located between the two layers of peritoneum in the mesentery. As the artery crosses over the duplicated intestinal tube from both sides to reach the main intestinal tube, the short branches entering the duplicated intestinal tube do not affect the blood supply of the main intestinal tube. This type accounts for 24.7% of duplication anomalies, with tubular type being the most common. The incidence of thoracic vertebral anomalies is as high as 91.6%.

　　1. Respiratory symptoms: In addition to abdominal symptoms, chest and abdominal duplication anomalies can also present with symptoms of respiratory or mediastinal compression. Sometimes, the main symptoms are chest symptoms, with the child experiencing difficulty breathing, asthma, cyanosis, and mediastinal displacement. It is easy to be misdiagnosed as pneumonia or mediastinal tumor.

　　2. Intestinal torsion can cause acute, complete, and strangulated intestinal obstruction symptoms and signs due to the gravitational action of duplicated intestinal tubes and the torsion of the elongated mesentery. It often occurs in newborns and infants. The onset is acute, the symptoms are severe, with severe vomiting and abdominal pain. The twisted mass can often be palpated in the abdomen.

　　3. Intussusception is prone to occur in intestinal cystic-type duplication anomalies at the distal ileum and ileocecal region. Some authors report that 17 cases (26%) of intestinal duplication anomalies developed intussusception, among which 15 cases were under one year old, accounting for 88.2%, all with typical clinical manifestations of acute intussusception. Intussusception caused by duplication anomalies often cannot be复位 by air or water enema. Occasionally, after successful reduction by enema, a mass remains in the abdomen, and a cystic mass can still be seen under B-ultrasound.

　　4. Perforation of the intestine is caused by the corrosive action of ectopic gastric mucosa and pancreatic tissue on the intestinal wall, leading to peritonitis. Some reports indicate that the site of perforation always has ectopic gastric mucosa, which has formed ulcers, and the perforation is located at the bottom of the ulcer. Clinically, it presents with symptoms and signs of acute peritonitis. In infants and young children, the signs may not be obvious, and it is not easy to distinguish from acute appendicitis perforation. A patient needs to be examined carefully and patiently.

　　5. Due to complex factors such as pathophysiological anatomy, location, pathological morphology, size, whether it communicates with the intestinal tract, and whether there are complications, the clinical symptoms of small intestinal duplication malformation vary greatly. Symptoms can appear at any age, with 60% to 83% occurring within 2 years, and many cases show symptoms within the first month of life. A few cases have no symptoms and are only found during abdominal surgery for other diseases.

　　1. Intestinal obstruction is often the clinical manifestation of cystic duplication malformation that does not communicate with the main intestinal tract, especially intestinal wall cysts. The cysts protrude into the intestinal cavity, blocking the intestinal cavity and causing varying degrees of intestinal obstruction. The cysts are prone to become the entry point for intussusception, manifested as acute symptoms of intestinal obstruction such as sudden vomiting, abdominal pain, and jam-like stools. The age of onset in these cases is usually young, with Zhao Li and others reporting 13 cases were all infants under 2 years old, with 5 to 9 months accounting for 61.5%. As the intestinal extracorporeal cyst gradually increases, it compresses the intestinal tract, causing obstruction. It can also be induced by gravity to cause intestinal torsion, leading to severe abdominal colic, vomiting, cessation of defecation and flatus, and even the appearance of watery stools mixed with blood, fever, thready pulse, shock, and other symptoms of poisoning.

　　2. Gastrointestinal bleeding The mucosal cavity is lined with ectopic gastric mucosa or pancreatic tissue that is connected to the main intestinal tract in the duplicated malformation. Gastrointestinal bleeding occurs due to the formation of ulcers. Holcomb collected 101 cases of gastrointestinal duplication malformation, 21 cases had ectopic gastric mucosa, of which 11 cases (52%) were found in ileal duplication malformation. He believes that hematochezia is often the first symptom of ileal tubular duplication malformation, commonly seen in children over 1 year old. Clinically, it is manifested as recurrent moderate hematochezia. The color of the stool depends on the bleeding site and amount. In cases with less bleeding at a higher position, it is tar-like stool, while in cases with lower position or more bleeding, it is dark red or bright red hematochezia. Infants and young children often manifest acute lower gastrointestinal bleeding, while older children are mainly complaining of intermittent blood stools accompanied by abdominal pain. Hemorrhage can often stop spontaneously, but it is prone to recurrent bleeding, which may cause anemia. Occasionally, persistent massive hematochezia may lead to shock.

　　3. Abdominal masses and abdominal pain Approximately 2/3 of cases have palpable masses in the abdomen. The cystic malformation is circular or oval in shape, smooth in surface and with a cystic feeling, without tenderness, with clear boundaries and certain mobility. The tubular malformation has an outlet connected to the main intestinal tract, allowing the secretion in the cavity to be discharged, so the chance of palpating the mass is less. If the outlet drainage is not smooth, the fluid in the malformed intestinal cavity accumulates in the abdomen and can be palpated as a string-like object. Once the outlet drainage is smooth, the mass shrinks, and the rapid enlargement of the cysts due to increased tension in the cyst wall may cause abdominal pain. Bleeding inside the cyst or inflammatory exudation due to trauma or infection may cause the mass to increase rapidly, abdominal pain to worsen, and be accompanied by abdominal muscle tension and tenderness. Once the cyst ruptures or perforates, it may lead to peritonitis.

　　4. In addition to abdominal symptoms, respiratory or mediastinal compression symptoms may also occur, sometimes mainly表现为胸腔症状, with symptoms such as dyspnea, asthma, cyanosis, mediastinal displacement, and it is easily misdiagnosed as pneumonia or mediastinal tumor.

　　19. 5. Associated anomalies: Intestinal duplication anomalies can be associated with intestinal atresia, malrotation, umbilical hernia. Sometimes, during emergency laparotomy for associated anomalies, duplication anomalies are found. Chest and abdominal duplication anomalies often occur with cervical, thoracic hemivertebrae or fused anomalies. There are not many cases of intestinal duplication anomalies presenting with abdominal masses. Children with malnutrition are more likely to feel active masses due to weak abdominal walls.

　　16. 1. Abstain from smoking and drinking: It is the primary measure to prevent laryngeal cancer. Smoking is the king of pungent and hot, and alcohol is the most damp and hot. Smoking and drinking have great harm to the throat.

　　15. 2. Light diet: Spices like ginger, pepper, mustard, garlic, and all spicy and hot foods can harm the mucosa of the throat. These spicy and fried foods should be avoided, and more fruits and vegetables rich in vitamin C should be eaten.

　　14. 3. Pay attention to oral hygiene: Pay attention to personal hygiene and wash hands frequently. You can rinse your mouth with saltwater in the morning and evening, and after rinsing, you can drink a glass of saltwater to clean and moisten the throat, improve the throat environment, and prevent bacterial infection.

　　13. 4. Strengthen physical exercise: Participating in physical exercise regularly is also one of the measures to prevent laryngeal cancer, enhancing the body's defense capabilities. Because the decrease in human immunity and the resistance of the throat are most likely to lead to the recurrence of throat diseases.

　　12. 5. Keep the indoor air fresh: In air conditioning environments, it is necessary to open the windows frequently for ventilation, place a basin of water in the room to increase humidity. At the same time, avoid inhaling dust, smoke, and irritating gases. If working in a dusty environment, wear a mask for protection.

　　9. X-ray examination: The abdominal plain film can show the compression and displacement of the intestinal tract, and in cases of incomplete intestinal obstruction, gastroscopy shows the intestinal tract with a curved indentation. Barium meal examination can show a barium filling defect or compression in a group of small intestines, especially the terminal ileum and ileocecal valve area, which should be paid special attention to. If there is barium filling outside the small intestinal tract or diverticula, and it appears with peristalsis, it has important diagnostic value.

　　X-ray film of the spine shows abnormal vertebral bodies, and further myelography, MRI, or CT examination should be performed to determine whether there is an enterocystoma within the spinal canal.

　　7. Ultrasound examination: Abdominal ultrasound examination shows the abdominal mass as cystic, and makes judgments on its location and size, which is conducive to diagnosis and differential diagnosis.

　　6. Radionuclide examination: When there is ectopic gastric mucosa in the duplicated intestinal tract, abdominal scanning after intravenous injection of 99mTc can often show radioactive accumulation areas in the duplicated intestinal tract, but it needs to be distinguished from Meckel's diverticulum, and it should be noted that negative results cannot negate the diagnosis.

　　4. Laparoscopic examination: If laparoscopic examination is possible, it can accurately determine the location and type of the lesion.

　　What are the good foods to eat for patients with intestinal duplication anomalies?

　　It is advisable to eat light and easily digestible foods, such as more vegetables and fruits like bananas, strawberries, apples, etc. Since they are rich in nutrients, eating more immune-boosting foods like propolis can enhance personal resistance to diseases. It is also important to have a well-balanced diet and ensure adequate nutrition in daily life.

　　2. Foods that should be avoided in small intestinal duplication malformation:

　　Avoid smoking and drinking, spicy foods, greasy foods, and smoking and drinking. Avoid eating cold foods to prevent recurrent attacks of the disease.

　　I. Treatment

　　Surgery is the only treatment method, about 80% of the cases are operated due to acute abdomen. Even asymptomatic small intestinal duplication malformations should be surgically removed to prevent complications and the occurrence of cancer later in life.

　　1. Resection of cystic malformation of repeated malformation Some small intestinal repeated malformations have separate mesentery and blood vessels, and the cyst can be completely excised. For those repeated malformations closely attached to the mesentery of the main intestinal tract, the operator should carefully search for the direct blood vessels nourishing the cyst between the main intestinal tract and the malformation cyst. Norris pointed out that when there is a clear gap between the main intestinal tract and the repeated malformation, it indicates that the malformation intestine has its independent blood vessels, which originate from the anterior lobe (or posterior lobe) of the mesentery and extend to the anterior wall (or posterior wall) of the malformation cyst. Conversely, the blood vessels nourishing the main intestinal tract originate from the posterior lobe (or anterior lobe) of the mesentery and extend to the main intestinal tract through the posterior wall of the malformation. If the operation is carefully identified and carefully operated, the malformation cyst can be separated and excised without damaging the blood supply of the main intestinal tract.

　　2. The resection and anastomosis of the repeated malformation and the main intestinal tract are difficult to be resected separately for the repeated malformations sharing nutritional blood vessels and muscle walls with the main intestinal tract and the repeated malformations within the intestinal wall. If the lesion range is small (length

　　3. The mucosal stripping operation for repeated malformations is extensive and affects most of the small intestine. The resection of the intestine will lead to short bowel syndrome, so only the mucosal stripping operation of the malformation intestine is performed. The muscle wall is longitudinally incised along one side of the repeated intestine to reach the submucosa, and the mucosa is sharply separated. An appropriate amount of normal saline is injected under the mucosa to facilitate mucosal stripping, and the mucosa is completely removed and excised. Then, part of the muscle wall of the repeated malformation is excised, and the incision margin is sutured or coagulated to stop bleeding. If there is a communication opening between the repeated malformation and the main intestinal tract, the mucosa of the repeated malformation is stripped off, and the connecting segment with the main intestinal tract is excised and an intestinal anastomosis is performed.

　　II. Prognosis

　　The short-term and long-term effects of intestinal duplication malformation surgery are good. According to Chinese literature, 9 out of 255 cases died, with a mortality rate of 3.5%. From 1966 to 1987, the Department of Pediatric Surgery of China Medical University treated 75 cases, with 2 deaths, all neonates, with a mortality rate of 2.66%.