Input loop syndrome

　　Acute input loop obstruction often occurs within 24 hours after surgery, but it can also occur several days or even years after surgery. The obstruction can be partial or complete, intermittent or permanent. Approximately 1% of patients develop obstruction near the gastrojejunal portion of the input loop after Billroth II surgery, with an anterior colonic anastomosis being more common than a posterior colonic anastomosis. When performing an anterior colonic anastomosis, due to the excessively long input loop, it can become twisted and obstructed behind the output loop when passing through the gap between the mesentery of the jejunal output loop and the transverse colon mesentery; if the gastrojejunal anastomosis or duodenojejunal loop is in a crossed position, with the input loop behind and the output loop in front, if the mesentery of the latter enters the looped intestinal tract, it can cause a closed obstruction of the jejunal part of the input loop. For patients with a posterior colonic anastomosis, obstruction can occur if the input loop retracts into the foramen of the transverse colon mesentery.

　　Due to the blockage of the outflow of pancreatic juice and bile in the jejunoileal loop, the accumulation of pancreatic juice and bile leads to acute expansion of the jejunoileal loop, causing severe upper abdominal pain that radiates to the interscapular region, frequent vomiting but in small amounts, and vomiting without bile. Symptoms do not subside after vomiting. There is marked tenderness in the upper abdomen, and sometimes an expanded jejunoileal loop can be felt. Due to excessive fluid accumulation in the jejunoileal loop, intestinal fluid can reflux into the pancreatic duct, making it prone to acute pancreatitis with a sharp rise in serum amylase. In cases of complete obstruction, the expanded jejunoileal loop can undergo necrosis and perforation, causing peritonitis and shock.

　　Chronic output loop obstruction usually occurs several weeks after surgery, but there are also cases that occur the following year or even longer. This type often occurs after Billroth II surgery with an angle, especially in patients with an anastomosis in front of the colon. It is caused by the jejunal loop protruding into the gap behind the gastrojejunal anastomosis. There are also a few cases caused by adhesions and jejunojejunal intussusception. When bile and pancreatic juice accumulate in the jejunal loop, it expands, stimulating peristalsis and causing the accumulated fluid to be expelled into the stomach, leading to vomiting of bile-containing fluid.

　　1. Acute pancreatitis (acute pancreatitis, AP):It is a common acute abdominal disease, accounting for the 3rd to 5th place in the incidence of acute abdominal diseases. More than 80% of the patients have mild illness, that is, acute edematous pancreatitis, which can be cured without surgery and is basically a medical disease. About 10% of the patients have severe pancreatitis, that is, acute hemorrhagic necrotic pancreatitis, where the inflammation of the pancreas is no longer reversible or self-limiting, often requiring surgical treatment and should be considered a surgical disease.

　　2. Peritonitis:It is inflammation of the parietal peritoneum and visceral peritoneum of the abdominal cavity, which can be caused by bacterial, chemical, physical injury, etc. It can be divided into primary peritonitis and secondary peritonitis according to the pathogenesis. Acute purulent peritonitis involving the entire abdominal cavity is called acute diffuse peritonitis.

　　3. Shock (shock):It is a clinical syndrome caused by insufficient tissue perfusion, which is a common complication in severe diseases in various clinical departments. The common feature of shock is insufficient effective blood volume, and although the blood perfusion of tissues and cells is compensated, it is still severely restricted, leading to poor blood perfusion of the whole body tissues and organs. This causes a series of pathophysiological changes, including tissue hypoxia, microcirculatory stasis, organ dysfunction, and abnormal cell metabolic function.

　　Patients generally manifest as strangulated high jejunal obstruction, which often occurs about 1 hour after a meal, with sudden喷射性 vomiting of bile-containing fluid. Nausea is often present before vomiting, accompanied by upper abdominal distension and pain that radiates to the back. Symptoms are immediately relieved after vomiting, until the next meal, when they recur. Physical examination shows tenderness in the upper abdomen, and sometimes an expanded jejunal loop can be felt on the right side of the upper abdomen.

　　Prevention of this disease:Some scholars have observed that the incidence of the proximal end to the larger curve during anastomosis is higher than that to the smaller curve, so it can be adopted to have the proximal end to the larger curve, which is related to the angle of the anastomosis. During gastrointestinal anastomosis, the angle between the anastomosis and the midline of the abdomen (parallel line) should be ≥45°; less than this angle is prone to form an entry obstacle. When closing the mesentery orifice after the colonic anastomosis, the fixed suture is made on the gastric wall above the anastomosis. Regarding the length of the enterotomy, some believe that the shorter it is, the better, as it is easier to form an angle. The length of the anterior colon should not be less than 15cm, and the length of the posterior colon should not be more than 12cm. The length of the jejunal segment after anastomosis should be ideal to overcome the traction force of the stomach.

　　When diagnosing intestinal loop syndrome, in addition to relying on its clinical manifestations, auxiliary examinations are also needed. Possible examinations during diagnosis may include abdominal plain film, barium contrast, CT, and ultrasound.

　　1. It is recommended to eat light and nutritious liquid foods, such as rice porridge, vegetable soup, lotus root starch, egg flower soup, noodles, etc.

　　2. Foods that are easy to digest and promote defecation, such as vegetables: kelp, pork blood, carrots, etc.; fruits: hawthorn, pineapple, papaya, etc.; eating foods rich in fiber, such as various vegetables, fruits, brown rice, whole grains, and beans, can help defecate, prevent constipation, stabilize blood sugar, and lower blood cholesterol.

　　3. It is recommended to eat foods rich in protein and iron, such as lean meat, fish and shrimp, animal blood, animal liver and kidney, egg yolk, dairy products, and foods like jujube, green leafy vegetables, and sesame sauce.

　　And it should be noted that fasting and water restriction are prohibited during the acute attack period.

　　Patients with intestinal loop syndrome generally present with绞窄性高位空肠梗阻，usually occurring about 1 hour after a meal, with sudden喷射性vomiting of bile-containing fluid. Nausea is often present before vomiting, with upper abdominal pain that radiates to the back, which subsides immediately after vomiting. Early surgical treatment should be sought for acute intestinal loop syndrome; for chronic cases, surgical treatment should be considered when medication is ineffective.