Meckel diverticulum

　　One, Etiology

　　In the early stage of embryogenesis, the inner cell mass at the top of the yolk sac is involved in the embryo in the second week of normal embryonic development, forming the primitive digestive tract. The head end is called the foregut, the tail end is called the hindgut, and the middle segment is called the midgut. The midgut communicates with the yolk sac, and there is a communication channel between them, known as the yolk duct or umbilical enteric duct. Under normal embryonic development, the yolk duct begins to involute and fibrotize spontaneously from the 6th to 8th week, and then gradually萎缩form a fibrous cord connecting the umbilicus and the midgut, and gradually absorb and regress from the umbilical end, finally disappearing completely. If there is an obstacle in the process of yolk duct absorption and regression, that is, incomplete absorption and regression or non-regression of the yolk duct, various types of abnormal yolk duct remnants will occur, such as umbilical fistula, umbilical sinus, umbilical polyp, yolk duct cyst, and ileal distal diverticulum. When the umbilical end of the yolk duct has been absorbed and regressed, while the intestinal end of the yolk duct remnant remains unsealed, Meckel diverticulum is formed.

　　Two, Pathogenesis

　　The Meckel diverticulum is mostly located on the ileal wall opposite the mesenteric margin of the terminal mesentery, 10-100 cm from the ileocecal junction, with about 5% of cases opening on the mesenteric side of the intestinal lumen. Due to the varying degrees of obstruction in the process of yolk sac regression, the morphology and pathological changes of the diverticulum are also different.

　　1. The manifestation of abnormal development of the yolk sac

　　(1) The blind end of the diverticulum is not connected to the intestinal wall and umbilicus: the diverticulum is free in the abdominal cavity, usually 2cm to 5cm long, in the shape of a cone, tubular cylinder, and sphere. There may also be its own mesentery tissue or vascular diverticular mesentery band tissue on the opposite edge of the mesentery.

　　(2) The yolk sac diverticulum does not close completely: the umbilical end is open, and one end is connected to a narrow pipeline of the intestinal tract, often with a small amount of intestinal fluid overflowing, known as yolk sac fistula or umbilical fistula. A few wider pipelines can excrete feces-like substances from the umbilicus, stimulating the skin around the umbilicus and causing erosion.

　　(3) Incomplete absorption and degeneration of the yolk sac umbilical end: there is a residual cord connecting the diverticulum and the umbilicus, known as umbilical yolk sac diverticulum and umbilical sinus.

　　(4) Complete occlusion of the yolk sac: but a small amount of mucosal tissue remains at the umbilicus, forming a bright red polypoid mass, often secreting a small amount of mucus-like secretions, known as umbilical meat or umbilical polyp.

　　(5) Yolk sac cyst: when both ends of the yolk sac degenerate and become occluded, and the middle part expands and has mucosal secretions forming a cyst, it is called a yolk sac cyst.

　　2. Pathological anatomy and histology: diverticula occasionally have a separate mesentery, and a vascular diverticular mesentery band is formed between the diverticulum and the ileal mesentery. This mesentery band is sometimes connected in a string-like manner. Clinically, it can become one of the causes of intestinal obstruction complications.

　　The histological structure of the diverticulum is the same as that of the distal ileum, consisting of the mucosal layer, submucosal layer, muscular layer, and serosal layer. The diameter of the diverticular orifice is generally smaller than that of the ileum. Heterotopic tissue is often present in the wall of the diverticulum, mostly gastric mucosal heterotopia, followed by pancreatic tissue, duodenal, and colonic mucosal tissue. The distribution of the heterotopic mucosal tissue in the diverticular wall is different, with the distribution of gastric mucosal tissue being wide, occasionally occupying a large part of the diverticular wall, and can also be scattered in an island-like distribution or segmental distribution. If it is pancreatic tissue, it is often located at the top of the diverticulum, and can be observed as a yellowish-white coin-like distribution under the serosa, with a sensation of hardness when touched.

　　The presence of heterotopic tissue in the diverticular wall is another main cause of complications in Meckel diverticulum. Heterotopic gastric mucosal tissue can cause diverticular erosion, ulceration, hemorrhage, and perforation. In Meckel diverticula with complications, ectopic gastric mucosal tissue accounts for 28% to 61%. Morris reported that in 208 cases of Meckel diverticulum, there were 65 cases (28.5%) with ectopic gastric mucosal tissue. Hunan Medical University (1997) reported that in 72 cases of Meckel diverticulum, there were 47 cases (65.3%) with ectopic tissue, among which the most common was ectopic gastric mucosa, accounting for 36 cases, followed by 11 cases of ectopic pancreatic tissue.

　　Due to the differences in the morphological location and pathological changes of various types of diverticula, different complex surgical acute abdomen can be manifested in clinical practice, summarized as follows:

　　1. Intestinal obstruction:When the vascular adventitia or inflammatory lesion of the diverticulum adheres to the intra-abdominal organs and tissues, a series of pathological changes can occur under the condition of small intestinal dysfunction, leading to various forms of mechanical small intestinal obstruction.

　　(1) Intestinal torsion: Intestinal torsion occurs around the residual cord of the yolk sac and the diverticulum, which is fixed at the umbilicus.

　　(2) Diverticular torsion: Most often, the diverticulum is in the shape of an inverted pear, with torsion around the diverticulum neck, which then affects the continuous patency of the ileum.

　　(3) Adhesive intestinal obstruction: Adhesion between the diverticulum and the surrounding intestinal tube or mesentery can cause small intestinal adhesive obstruction.

　　(4) Internal hernia: The mesenteric cord and the intestinal tube or mesentery are adhered together, causing part of the intestinal tube to herniate between the intestinal cords, forming an internal hernia, which often leads to the occurrence of strangulated intestinal obstruction.

　　(5) Intussusception: Due to the inversion of the diverticulum, it obstructs the patency of the intestinal lumen, and with the advancement of intestinal peristalsis, it forms intussusception.

　　(6) Diverticular hernia: The diverticulum enters the inguinal canal through the internal ring orifice, forming a special type of inguinal hernia, known as diverticular hernia (Litter hernia), which can develop into an incarcerated hernia or strangulated hernia.

　　(7) Diverticular prolapse: In cases where the diverticular lumen is wide, the proximal and distal ends of the small intestine can prolapse through the diverticulum to the umbilicus, leading to intestinal obstruction.

　　2. Ulcerative bleeding of diverticulum:The ectopic gastric mucosal tissue in the wall of the diverticulum has the function of secreting gastric acid and digestive enzymes. The exocrine secretion of the ectopic pancreatic tissue also has digestive enzyme activity. These digestive enzymes continuously act on the mucosal and submucosal tissues in the inner wall of the diverticulum, producing peptic ulcers. The ulcers gradually expand and deepen, causing the diverticular wall to erode and invade blood vessels, leading to bleeding. This bleeding often manifests clinically as painless massive lower gastrointestinal bleeding.

　　3. Diverticular perforation and peritonitis:This condition is also due to the secretion of digestive enzymes by the ectopic gastric mucosa and pancreatic tissue in the inner wall of the diverticulum. This gradually invades the entire wall of the diverticulum, leading to diverticular perforation, with intestinal fluid flowing into the peritoneal cavity, causing changes in peritonitis.

　　4. Diverticulitis:It is often caused by inflammation, mucosal edema, and congestion due to foreign bodies in the diverticulum, parasites, etc. The narrowing of the diverticulum lumen affects the excretion of the contents of the diverticulum. Literature reports that there are hard fruit shells, copper coins, and necrotic ascaris in the diverticulum lumen, leading to the occurrence of diverticulitis. On the basis of diverticulitis, further development of inflammation can also lead to diverticular perforation and peritonitis.

　　When Meckel's diverticulum develops complications, various acute abdominal symptoms may occur. The complications include the following aspects:

　　1. Intestinal obstruction

　　Complications of Meckel's diverticulum are commonly low intestinal obstruction. In China, intestinal obstruction accounts for 40% to 64% of its complications. Ninov (1990) reported 64 cases, with intestinal obstruction accounting for 65%, and Frank reported that intestinal obstruction accounted for 35% of the 34 cases operated on.

　　Intussusception: It is a common type of intestinal obstruction caused by Meckel's diverticulum. Since the diverticulum is often located at the end of the ileum, the diverticulum is conical in shape, and the base is wider. When the intestinal function is disordered and peristalsis is enhanced, the diverticulum can be flipped over and inserted into the ileum, becoming the starting point of intussusception. The flipping of the diverticulum into the intestinal lumen causes obstruction of the intestinal lumen, and the enhanced peristaltic function pushes the proximal diverticulum into the distal intestinal lumen, forming a sigmoid intussusception. As the inserted intestinal tube further advances, when it continues to enter the colon through the ileocecal valve, it forms a sigmoid-coecal intussusception. Sometimes, the diverticulum does not flip into the ileum but is inserted into the distal ileum with the intestinal tube, forming an intussusception.

　　Concurrent intestinal intussusception of Meckel diverticulum often occurs after infancy, and it is still characterized by paroxysmal abdominal pain (paroxysmal crying), vomiting, and raspberry jam-like stools. Physical examination: careful palpation of the abdomen can often feel a sausagelike mass at the intussusception site. Rectal examination is difficult to differentiate from rectal conditions.

　　2. Diverticulitis

　　Generally, the base of Meckel diverticulum opens into the ileum, which is wider, making it easier for secretions to flow into the ileum and be excreted, rather than accumulating in the diverticulum. When the anatomical shape of the diverticulum is finger-like or gourd-like, the opening is narrow, or there is obstruction at the neck of the diverticulum, or there are foreign bodies and intestinal parasites, etc., the clinical manifestations are very similar to acute appendicitis. Most of them are abdominal surgery for appendicitis. Frank reported that 8 cases of diverticulitis were misdiagnosed as acute appendicitis before surgery. Clinically, the pathological results of diverticula resected due to diverticular complications all show diverticular inflammatory changes. Ma Yong and others believe that diverticulitis is the basic lesion of various complications of Meckel diverticulum. Han Mao tang (1984) reported that among the 50 cases of surgical complications, diverticulitis accounted for 17 cases, indicating that the incidence of diverticulitis is also relatively high.

　　Diverticulitis is commonly seen in older children, presenting as acute or subacute attacks, often manifested as right lower quadrant abdominal pain, nausea, vomiting, low fever, tenderness in the right lower quadrant near the umbilicus on abdominal palpation, increased white blood cell count. Therefore, it is often misdiagnosed as acute appendicitis and subjected to surgery. When the appendix is found to be normal and clinical signs are severe, the terminal ileum and ileocecal region should be explored to avoid missing this disease, which may further develop into serious consequences such as diverticular necrosis and perforation.

　　3. Concurrent umbilical fistula of Meckel diverticulum

　　This disease is caused by congenital atresia of the vitelline duct and an open umbilicus. Clinically, it is a chronic process, with a small amount of yellow, smelly intestinal fluid oozing from the umbilical orifice, and occasional gas discharge. The diverticulum should be removed along with the fistula, and it should be differentiated from the urachus before surgery: a suitable catheter can be inserted from the fistula, and 76% diatrizoate solution can be injected for X-ray contrast examination to clarify the diagnosis; or methylene blue solution can be injected into the bladder, and observe whether there is methylene blue solution oozing from the umbilicus.

　　4. Foreign body embedded in the lumen of Meckel diverticulum

　　Velanovich reported a 9-year-old child who mistakenly ate a coin and sought medical attention due to right lower quadrant abdominal pain. After examination, a coin was found in the gastrointestinal tract. The coin remained in the same position for two days before surgical treatment, and it was confirmed during surgery that the coin was embedded in the diverticulum. Similarly, eating hard shell fruit skins and other substances may also be embedded in the diverticulum and difficult to expel, resulting in clinical symptoms.

　　5. Malignant transformation of diverticulum

　　There have been no reports of malignant transformation of Meckel diverticulum in children in China. Among the 1605 cases of Meckel diverticulum complications collected by Moscs, there were 52 cases of diverticulum tumors (3.2%), which can manifest as abdominal pain, hematochezia, symptoms of intestinal obstruction, and so on, due to their different tumor nature and degree of manifestation.

　　1. Cultivate good living habits, quit smoking and limit alcohol intake. Smoking, according to the World Health Organization, if people stop smoking, cancer in the world will decrease by one-third within five years; secondly, do not overindulge in alcohol. Cigarettes and alcohol are highly acidic substances, and people who smoke and drink for a long time are prone to develop an acidic constitution.

　　Do not eat too much salty and spicy food, do not eat overheated, cold, expired, and deteriorated food; for the elderly and weak or those with certain genetic disease genes, eat some anti-cancer foods and alkaline foods with high alkaline content appropriately, and maintain a good mental state.

　　1. Small bowel air-barium double contrast imaging

　　Due to the fact that small bowel barium meal imaging is observed at different times, through透视 observation of the position, shape, and peristalsis of the small bowel, and occasionally affected by the filling and expansion of the small bowel, making the observation unsatisfactory, the display of the distal small bowel is affected by the interference of gastrointestinal fluids, the absorption of barium water, and it is easy to miss the diagnosis. While the double X-ray examination method of small bowel barium enema can usually show the shape and lesions of the small bowel well, the X-ray imaging characteristics of the double-contrast examination of the small bowel of Michael's diverticulum include: the distal ileum protrudes outward into the intestinal lumen, with a sac-like structure perpendicular to the long axis of the intestinal tract, known as the T sign; the junction of the diverticulum and ileum presents a narrow neck sign, or a triangular mucosal area; occasionally, a large pleat can be seen in the diverticulum, similar in shape to gastric mucosa. Li Ruisheng (1992) reported that this examination method is the most effective X-ray examination method for the diagnosis of this disease.

　　2. 99mTc radionuclide scanning

　　Jewett (1970) used 99mTc for abdominal radionuclide scanning to diagnose Meckel diverticulum. 99mTc has a special affinity for gastric mucosal wall cells and can be absorbed, utilized, and secreted to form a radioactive concentration area. Due to the presence of ectopic gastric mucosal tissue within the diverticulum wall, which also has secretory function, a radioactive substance dense area can be found in the lower right abdomen or middle abdomen near the umbilicus during 99mTc radionuclide scanning, which can make a clear diagnosis and determine the location and extent of the lesion, but it is necessary to exclude false-positive factors and other lesions.

　　3. Ultrasound examination

　　Although it is difficult to detect the existence of diverticula, it is often possible to make morphological judgments for cases with inflammation, obstruction leading to proximal intestinal loop dilatation or mass, and foreign bodies embedded in the diverticulum. For example, the intestinal wall in the diverticulum area is edematous, the mucosa is rough and disordered, the intestinal loops are adherent in clumps, the proximal intestinal tract is dilated and shows retrograde peristalsis, and there are strong echo areas in the diverticulum, which are conducive to diagnosis and differential diagnosis.

　　4. Angiography

　　Selective superior mesenteric artery angiography can also be performed for Michael's diverticulum hemorrhage cases, which can show the location and morphology of the diverticulum. If there is progressive hemorrhage, more than 0.5ml per minute, it is often possible to see bleeding points and patchy shadows within the wall, and if the amount of bleeding is less, the contrast agent accumulates in the diverticulum in a cloud-like shadow. Kusumoto believes that angiography has a high diagnostic value for the detection of diverticula and hemorrhage. Other authors have reported 39 cases of angiography, with a diagnostic rate of 59%. Although angiography is a traumatic examination method, the currently used vascular puncture technique can achieve minimal trauma and safety, so most scholars believe that this method is a relatively valuable diagnostic method for this disease.

　　5. Laparoscopic examination

　　The diverticular lesion can be directly visualized, and the diverticulum can be removed under direct vision through laparoscopy.

　　Diet should be light. For the first few days after surgery, diet should be adjusted according to individual condition, with a focus on liquid and semi-liquid foods. Eating more high-protein foods is beneficial for wound healing. Supplementing a variety of vitamins, eating more fresh vegetables and fruits. It is permissible to eat various lean meats, milk, eggs, and other high-protein foods. Avoid greasy foods, and do not choose foods such as preserved bean curd, scallions, chili peppers, and chives, as they are不利于 wound healing and can easily cause infection.

　　First, treatment

　　Children with Meckel's diverticulum often seek medical attention due to complications such as intestinal obstruction, ulcer hemorrhage, and perforation. Once a clear diagnosis is made, surgical treatment should be performed immediately, and most of them are operated on in an emergency situation. However, there are very few cases with a clear diagnosis of Meckel's diverticulum before surgery, so the operation often has the nature of laparotomy exploration.

　　1. Preoperative preparation:Complications of Meckel's diverticulum are one of the common causes of acute abdominal pain in pediatric surgery. Children often have severe water, electrolyte, and acid-base imbalances, and there is also the presence of an inflammatory focus. The child's overall condition is poor, so careful preoperative preparation is essential. For cases of complete mechanical intestinal obstruction or peritonitis, emergency surgery should be performed within 2-4 hours after admission.

　　(1) Diverticulum with intestinal obstruction: It can manifest as various types of intestinal obstruction and is prone to绞窄性肠梗阻 with intestinal infarction and necrosis. Most children have symptoms of dehydration and acidosis, so intravenous fluid replacement and acid correction should be given before surgery. For those with anemia and low blood pressure, intravenous fluid replacement of 10-20ml/kg body weight can be administered before surgery to supplement blood volume. At the same time, a gastrointestinal decompression tube should be placed before surgery, and antibiotics should be administered intravenously.

　　(2) Diverticulum with massive hemorrhage: First, the progressive hemorrhage from the diverticular ulcer should be controlled. Clinically, attention should be paid to monitoring vital signs. Hemostatic drugs, blood transfusion, and blood substitutes should be used to supplement blood volume and prevent and correct hypovolemic shock. Once the general condition improves, hemoglobin is above 80g/L, and blood pressure is normal and stable, emergency surgical treatment should be performed. For progressive hemorrhage that is difficult to correct clinically, and for which a clear diagnosis has been made, surgery can be considered while actively treating shock, removing the focus, and stopping the hemorrhage.

　　(3) Diverticulitis and perforated peritonitis: Due to severe infection, the condition of children is often serious, and even toxic shock may occur. Broad-spectrum antibiotics and metronidazole should be administered intravenously before surgery. Rehydration, correction of electrolyte imbalance and acidosis, and blood transfusion are required. If there is a high fever, physical cooling should be applied to control body temperature below 38.0℃; if there is rapid breathing, oxygen should be administered. The preoperative preparation should be completed within 4 hours of admission, and then surgery should be performed.

　　2. Surgical principles:All diverticula accompanied by surgical acute abdomen should be surgically resected to relieve obstruction, eliminate inflammation and bleeding foci.

　　(1) Lesions of diverticula with the following conditions should be resected, and primary anastomosis of the ileal segment should be performed at the same time: ① The basal lesion area of the diverticulum involves the ileum, such as local ileal hypertrophy, scar stenosis, and ileum involvement with the presence of ectopic tissue; ② Perforation of the diverticular base or obvious inflammatory infiltration and edema in the wall of the connecting ileal segment; ③ Blood supply disorders, ischemic necrosis, or bleeding in the diverticulum and the corresponding ileal segment; ④ Intussusception or intestinal volvulus caused by the diverticulum, although there is no intestinal necrosis after reduction, but local intestinal tubes have appeared obvious ischemic and compressive damage, if the intestinal segment is retained, it is feared that there may be intestinal perforation and necrosis; ⑤ The opening of the diverticular base is wide and the diameter exceeds the lumen of the intestine.

　　(2) Symptomatic diverticula and umbilical enteric fistula: Perform diverticulectomy and fistula excision.

　　(3) Abdominal surgery for other reasons found to have a diverticulum: Whether there are lesions or clinical symptoms, the diverticulum should be resected to prevent future complications.

　　(4) Perform various surgical procedures for diverticular complications: If the ileocecal region has no obvious inflammation, edema, or adhesion, and if the child can tolerate the operation, appendectomy can be performed at the same time.

　　3. Surgical methods:Meckel diverticulum must be completely resected, otherwise, the residual lesions and ectopic ectopic tissue may cause the recurrence of complications.

　　Several methods of diverticulectomy:

　　(1) Simple diverticulectomy: The diverticulum is finger-like, resembling an appendix or pedunculated polyp. The method of resecting the appendix can be used to remove this type of diverticulum, and then the remaining end is sutured and buried in a purse-string manner. However, there are two disadvantages in suture and burial of the ileum: first, a part of the diverticular base is necessarily retained, which may still contain ectopic tissue that can cause ulcer bleeding complications; second, after suture and burial, it can cause narrowing of the ileum lumen and can also become a source of disease for intestinal intussusception in the future. Therefore, most scholars do not advocate for this method at present.

　　(2) Diverticulum oblique excision and anastomosis: Suitable for diverticula with a wide base and the lesion is limited to the diverticulum itself. Use two intestinal clamps to clamp the base of the diverticulum obliquely. The diverticulum is resected close to the edge of the clamp. After the cut surface is disinfected with 3% iodophor or phenol (carbolic acid), full-thickness interrupted结节 sutures are performed, and then the seromuscular layer is buried. This method is simple and easy to perform and is a commonly used method for this disease (Figure 3).

　　(3) Diverticulum wedge resection: Use two intestinal clamps to clamp the ileum at both ends of the diverticulum, with the tip of the clamp placed at the margin and the handle placed on the opposite side of the mesentery in the shape of a V. The base of the diverticulum and the adjacent part of the small intestine are completely resected to avoid the recurrence of diverticular ectopic tissue, which may cause ulcer bleeding or perforation. The two cut surfaces are brought together and sutured in full thickness with结节 sutures, and then the seromuscular layer is buried. This surgical method is recommended by most scholars.

　　(4) Laparoscopic resection: If a simple Meckel diverticulum is found during laparoscopic examination, and if the conditions are met and the doctor is skilled in the operation, this surgery can be performed.

　　(5) Diverticulectomy and intestinal resection: When diverticular complications involve adjacent intestinal segments, such as necrosis of adherent intestinal tract, severe inflammation and edema, and ectopic gastric mucosa causing diverticular hemorrhage affecting the ileal segment, it is necessary to decisively perform diverticulectomy and intestinal resection, and primary end-to-end intestinal anastomosis.

　　4. Surgical complications and their management

　　(1) Diverticular remnant syndrome: Incomplete resection of diverticula, residual diverticular base tissue, leading to postoperative diverticular remnant syndrome. It is manifested by local discomfort and pain. In addition, the remaining diverticular metaplastic gastric mucosal tissue can cause recurrence of diverticular remnant or ulcer symptoms after surgery, and radical reoperation should be performed again in all cases.

　　(2) Anastomotic intestinal lumen stenosis: The diverticulum is not resected strictly in an oblique or wedge shape to ensure the patency of the intestinal tract, causing narrowing of the intestinal lumen at the anastomotic site, affecting the passage of intestinal contents. Mild cases can be treated conservatively, while severe intestinal obstruction should undergo resection of the stenotic segment and end-to-end intestinal anastomosis.

　　(3) Anastomotic technique error: On the one hand, after resection of the diverticulum, anastomosis is not performed according to the principle of 'longitudinal incision and transverse suture', causing narrowing of the intestinal lumen; on the other hand, the two-layer suture method of the intestinal wall, with too much full-thickness结节缝合 tissue and deep submucosal layer embedding, forms too much tissue protruding into the intestinal lumen, affecting the patency of the intestinal tract.

　　(4) Anastomotic leakage: If the operator does not correctly master the surgical principles, resection and anastomosis are performed at the base of the diverticulum or intestinal segment with severe infection, tissue edema, or poor blood supply, which is easy to cause anastomotic leakage and serious consequences. Therefore, it is necessary to accurately determine the pathological changes and viability of the intestinal tract during surgery, and to perform intestinal resection and anastomosis away from the severely diseased intestinal tract.

　　(5) Abdominal residual infection: Due to contamination of the abdominal cavity with intestinal contents during surgery, or perforation of diverticula, incomplete cleaning of pus in the abdominal cavity, postoperative residual inflammation in the abdominal cavity, such as subphrenic infection, pelvic abscess, etc. The abdominal cavity should be thoroughly cleaned with warm saline and antibiotics during surgery. If there is any doubt, abdominal drainage can be placed.

　　(6) Intestinal obstruction: If the operation is rough, widely irritating and pulling the intestinal tract causes serous membrane congestion and injury, or if the position of the intestinal tract is not properly aligned before closing the abdomen, causing postoperative intestinal twisting and angulation leading to intestinal obstruction, it should be resolved according to the method of adhesive intestinal obstruction.

　　II. Prognosis

　　Patients with complications have poor prognosis, and they are more common in infants and young children. They must undergo timely surgical treatment, and the mortality rate is 10% to 15%, which has decreased to 1% to 2% in recent years.