Merkel's diverticulum is a common malformation of small intestine development caused by embryonic vitelline duct remnants, and occurs in humans3 5. Most people live their lives without symptoms. In the second week of normal embryos, the endoderm cells at the top of the yolk sac are involved in the embryo body and form the original digestive tract, with the tail end called the hindgut and the middle segment called the midgut, and connected to the yolk sac. At the 4th week of the embryo, the yolk sac of the connected part gradually narrows to form a tubular structure called the yolk duct or umbilical canal. In the 6th week, the yolk duct will occlude itself and shrink into a fibrous cord connecting the umbilicus to the midgut, known as the yolk sac cord. The cord will start to absorb from the umbilicus until it disappears completely. If the yolk sac duct is impaired during occlusion and absorption, the vitelline duct is incomplete or non-degenerate, resulting in various types of yolk sac malformations. When the vitelline duct absorption degenerates and the intestinal end does not close, a Merkel diverticulum is formed.
At the same time as the vitelline duct develops, the vitelline duct artery from the celiac artery divides into left and right branches, which follow the mesentery sides to the vitelline duct and lead to the umbilicus to wrap around the vegetative vitelline duct. The left branch of the vitelline duct artery gradually atrophied and disappeared at the 6th and 8th week of the embryo, and the right branch developed into the superior mesenteric artery, which still has a passage to the vitelline duct. When the vitelline duct completely degenerates, the arterial branches that accompany the vitelline duct also disappear. If the vitelline duct remains to form a Merkel diverticulum, the arterial branch may also remain, and in some cases a vascular diverticulum mesangial band forms between the Merkel diverticulum and the ileusentery, which is a major factor in intestinal obstruction.
Merkel's diverticulum is generally located in the ileal segment 10 l00 cm from the ileocecal valve. Histologically, diverticula are structurally identical to the normal small intestinal wall, including mucosa, submucosa, muscle, and serous layers, and the diverticulum is usually covered by the ileal mucosa. About 1 4 l 3 of the diverticulum was present with vasophytic tissue, among which the vasophytic gastric mucosal tissue was the most common, followed by pancreatic tissue, and duodenum, jejunum, and colon tissue.
1) Clinical manifestations.
1. Intestinal obstruction.
Merkel's diverticulum is often complicated by intussusception. This type of intussusception starts at the diverticulum, and the proximal bowel is inserted into the distal bowel, which can be chronic intussusception. Chronic disease is often chronic in people older than two years of age, with abdominal pain as the main symptom, which can last for weeks or months. Initially, it is colic, but gradually relieves and the pain decreases, and it may be accompanied by vomiting, and the stool is sometimes mixed with bloody mucus. Abdominal examination may reveal abdominal distention, bowel pattern, focal tenderness, rebound tenderness, and a palpable mass in some children. Hyperintestinal sounds. Plain x-rays of the abdomen in an upright position show intestinal gas and fluid levels. Air enema may show images of gas obstruction in the intussusception bowel and cup-mouth signs. Medical history is followed, and some children have a history of recurrent intussusception. Rarely, abdominal pain is relieved after an enema.
Closed loop intestinal obstruction is the formation of an internal hernia between the space below the diverticulum or cord by a loop of the small bowel, and a closed loop obstruction of the bowel compressed by the cord. This type of intestinal obstruction can occur suddenly, with severe abdominal pain and vomiting occurring within hours of intestinal necrosis, and the condition deteriorates rapidly, leading to dehydration, acidosis, and toxic shock. Children are often pale, sweating, distressed, and flexed due to dehydration. In the early stages of the disease, the abdomen is soft and tender, and the intestinal loops may be palpable. When intestinal circulation disorders, intestinal perforation, and peritonitis occur, peritoneal irritation signs, moving dullness, and absent or decreased bowel sounds may occur. X-rays may show pneumaticus and a fixedly located stepped fluid level, with closed loops forming a C-shape, concentric circles, and signs of jejunileal inversion. Ultrasonography can understand the distribution of liquids and gases and the blood circulation of the intestinal tract, which has certain significance for diagnosis.
The symptoms and diagnosis of adhesive intestinal obstruction are the same as those of general adhesive intestinal obstruction.
2. Diverticular ulcer bleeding.
It mostly occurs in infants and young children under 2 years old, and the clinical manifestations are a sudden occurrence of ** large amount of blood in the stool, there is no prodromal symptom before the blood in the stool, and the blood in the stool is often dark red at the beginning, and then bright red, and the amount of blood in the stool is about 100ml or more each time. 5 to 6 times a day, some children with hematochezia combined with diverticular perforation may have peritoneal irritation.
3. Perforation of diverticular ulcer.
Unlike perforation of appendicitis, perforation of diverticulum ulcer is not an inevitable consequence of the development of diverticulitis, but rather perforation due to peptic ulcer. These complications can occur in children of all age groups, including neonates and infants, and diagnosis is difficult. Due to the poor development of the omentum in young children, the inflammation cannot be quickly encapsulated, and once perforation occurs, severe diffuse peritonitis can develop within a few hours, with abdominal pain, bloating, vomiting and abdominal muscle tension. X-rays show discreted gas from the diaphragm. Similarly, due to the poor ability of the omentum to limit inflammation in young children, the toxin is quickly absorbed, and toxic shock occurs and is life-threatening.
4. Diverticulitis.
Paroxysmal abdominal pain in the right lower quadrant progressively worsens, nausea, vomiting, low-grade fever, elevated white blood cell count, and abdominal tenderness, rebound tenderness, and abdominal muscle tension on abdominal examination, which are very similar to acute appendicitis, and are often misdiagnosed.
b) Diagnosis. If the child suddenly develops an asymptomatic profuse stool with dark red stools and then bright red, diverticular ulcer bleeding should not be ignored. So far, there are not many effective methods for diagnosing Merkel's diverticulum, and diverticula is often difficult to diagnose without complications. Complications can be based on abdominal pain, vomiting, cessation of gas, history of defecation and signs of abdominal distention, gastrointestinal pattern and peristaltic waves, hyperbowel sounds, and the sound of breath and water. Abdominal x-ray shows gas-pneumogas, with several stepped fluid levels in the abdomen, and the diagnosis of intestinal obstruction is not difficult for complications of marktel's diverticulum. On this basis, if the child is over 2 years of age and has a history of intussusception or chronic abdominal pain, a history of paroxysmal abdominal pain, bloody stools, abdominal mass, etc., Merkel's diverticulum complicated by intussusception should be considered. Air enema** is present with obstruction of the gas and the opacity of the cup. Diverticular perforation is accompanied by peritoneal irritation and sometimes free air is visible subdiaphragm on an upright view of the abdomen. In summary, x-rays can only assist in diagnosing complications of Merkel's diverticulum, such as intestinal obstruction and diverticular perforation. Ultrasonography can help diagnose intussusception with a bullseye sign. It is difficult to distinguish diverticulitis from appendicitis, and from a foreign body in the diverticulum from fecal stones in the appendix. Because the meckel diverticulum is mostly covered with vashered tissue, showing the concentration of radioactive substances, if there is a hyperphysis of gastric mucosa, the accuracy of diagnosis through the 99MTC radioactive concentration area is 70 80, because the intestinal repetition malformation of the intestine is also covered with ectopic gastric mucosa, and there are also manifestations of radioactive concentration area, and attention should be paid to identification during diagnosis.
3) Differential diagnosis.
1. Diverticular hemorrhage.
It needs to be differentiated from acute intussusception. Ulceration and bleeding occurred in the ectopic gastric mucosa and pancreatic tissues, most of which were massive blood in the stool. At first it was dark purple in color, and later it turned bright red. Sometimes bleeding up to 100 milliliters at a time, hemorrhagic shock occurs for a short period of time, and bleeding often stops spontaneously or repeatedly intermittently. However, the acute inussusception blood stool is jam-like, and the child has clinical signs of paroxysmal crying, abdominal pain, and a palpable sausage-like mass in the abdomen.
2. Diverticulitis.
Inflammation of Merkel's diverticulum is mainly manifested by pain in the periumbilical and right lower quadrant, often accompanied by nausea and vomiting. Abdominal examination may show tenderness and abdominal tension in the right lower quadrant and subumbilicus. These signs and symptoms are difficult to distinguish from acute appendicitis, and it has been reported that rings of redness and swelling around the umbilical foramen are characteristic of Merkel's diverticulitis.
3. Perforation of acute appendicitis.
Acute appendicitis has a history of metastatic right lower quadrant pain, early nausea and vomiting, and body temperature can rise more than 12 hours after the onset of the disease, and diverticulitis and ulcers lead to diverticular perforation, most of the perforations occur suddenly, and the clinical manifestations are severe abdominal pain, vomiting, and fever, abdominal examination found that the symptoms of abdominal peritoneal irritation are obvious, abdominal muscle rigidity, and a few cases can occur pneumoperitoneum.