Malabsorption syndrome after gastrectomy

　　First, Etiology

　　Causes affecting digestive tract absorption after gastrectomy:

　　1. Impaired gastric function and accelerated gastric emptying.

　　2. The asynchrony of biliary and pancreatic secretion after meals.

　　3. Changes in several factors in the jejunal lumen after gastrectomy can lead to malabsorption syndrome.

　　Second, Pathogenesis

　　1. Impaired gastric function and accelerated gastric emptying: After gastrectomy, the secretion of gastric acid and pepsin decreases, gastric emptying is fast, which weakens the digestive function of food, leads to the bypass of the duodenum, and food enters the small intestine directly. The stimulation of pancreatic and biliary secretion is lacking or weakened, leading to a decrease in the concentration of bile salts, lipase, and trypsin in the contents of the proximal small intestine. The mixture of chyme with bile salts and enzymes is incomplete, insufficient emulsification of fat, leading to malabsorption.

　　2. The study on the effect of the liquid test meal on the biliary and pancreatic secretion of patients after gastric surgery proves that:

　　(1) Accelerated gastric emptying after gastrectomy: In the normal control group, it takes 75.3 minutes for gastric emptying after the liquid test meal; for Billroth I and II gastrectomy patients, it takes only 43.1 minutes and 44.3 minutes, respectively.

　　(2) In the normal control group, after 20 to 30 minutes following the liquid test meal, the trypsin concentration in the proximal jejunal fluid increased from 21U/ml to 50U/ml, and it remained at a high level 2 hours later; while for Billroth II gastrectomy patients, after 20 to 30 minutes following the liquid test meal, the trypsin concentration in the proximal jejunal fluid was lower than that in the normal control group. The trypsin concentration in the jejunal digestive fluid on an empty stomach began to slowly increase only after 50 minutes following the liquid test meal, which was higher than that in the Billroth I gastrectomy patients. To exclude the dilution effect of the accelerated gastric emptying after gastrectomy on trypsin concentration, trypsin concentration in the proximal jejunal digestive fluid was detected after CCK administration in patients undergoing Billroth I and II surgeries, indicating that the trypsin concentration in the proximal jejunal digestive fluid of patients undergoing Billroth I and II surgeries was the same as that in the normal control group, suggesting that the reduced secretion after gastrectomy led to a decrease in trypsin concentration in the jejunal digestive fluid.

　　(3) The concentration of bile salts in the proximal jejunal digestive fluid of patients after Billroth I and II surgery is also lower than that of the normal control group. This postprandial pancreatico-biliary secretion imbalance constitutes relative insufficiency of pancreatic function, decreased concentration of bile salts, leading to reduced absorption capacity for fats, sugars, and proteins.

　　3. Small intestinal factors: Many factors in the small intestinal lumen change after gastrectomy, which can lead to malabsorption syndrome. These factors include:

　　(1) Accelerated transport in the proximal small intestine: The absorption time of glucose is lost due to malabsorption.

　　(2) Lack of lactase in the small intestine leads to reduced lactose tolerance.

　　(3) Bacterial proliferation in the small intestine:

　　① Increase in bacterial count in the small intestine after gastrectomy: According to statistics, the incidence of bacterial proliferation in the small intestine of Billroth II gastrectomy patients is 30% to 50%. The normal upper jejunum has a bacterial count of 10^4/ml, and the upper jejunum has a bacterial count of 10^8 to 10^9/ml after gastrectomy with vagotomy and truncal vagotomy, and subtotal gastrectomy.

　　② Increase in bacterial species in the small intestine after gastrectomy: The normal jejunum only has 2-3 strains, mainly Gram-positive cocci, facultative anaerobic lactobacilli, and anaerobic bacteroides. After gastrectomy, especially in patients with blind loop syndrome, various aerobic and anaerobic bacteria that are usually found in the colon are present in the jejunal digestive fluid. This change in the small intestinal ecological environment is related to the reduction in gastric acid secretion after gastrectomy, changes in intestinal dynamics, and the loss of the scavenger function of the peristaltic complex during the small intestinal digestion period.

　　③ The impact of bacterial proliferation in the small intestine on absorption: Bacterial proliferation in the small intestine damages the active transport of monosaccharides and amino acids into the cells. Gianella's research proves that after gastrectomy, there is bacterial proliferation in the small intestine, and the villous edge of the small intestine is damaged in terms of the transport function of glucose and leucine, and the level of vitamin B12 decreases. Antibiotics can correct some of these changes, proving that bacterial proliferation in the small intestine has a negative impact on the absorption of sugars and proteins.

　　④ The impact of bacterial proliferation in the small intestine on bile acid metabolism: Fats and fat-soluble vitamins must be mixed with bile salts to form mixed bile salt micelles for absorption. When there is excessive bacterial proliferation in the small intestine, the bacteria can convert primary bile acids into secondary bile acids (i.e., cholic acid, deoxycholic acid, lithocholic acid), and the secondary bile acids do not participate in the formation of bile salt micelles, thus cannot form mixed micelles (mixed micelles) containing fatty acids, monoacylglycerols, lecithin, and cholesterol, fat-soluble vitamins, which are absorbed, leading to malabsorption of fats and fat-soluble vitamins.

　　Post-gastrectomy malabsorption often leads to complications such as malnutrition, weight loss, emaciation, and osteoporosis.

　　1. Water and electrolyte imbalance:Patients with this condition often have hypoproteinemia, an increase in the total extracellular fluid volume, leading to a hypotonic state. When vomiting and diarrhea occur, it is easy to cause hypotonic dehydration and severe electrolyte disorder. Low blood potassium, low blood sodium, low blood calcium, and low blood magnesium can cause corresponding symptoms.

　　2. Often accompanied by other nutrient deficiencies:Especially common is vitamin A deficiency, which can cause dryness and softening of the cornea of the eye, and even perforation. It often accompanies cheilitis caused by vitamin B deficiency, and because of the slow growth and development, rickets is rare and often accompanied by nutritional anemia.

　　3. Due to low systemic immune function, it is prone to various acute and chronic infections and infectious diseases:Especially common are intestinal and respiratory tract infections, easy to transmit measles, tuberculosis, and other infectious diseases and parasitic diseases. Digestive tract or systemic fungal infections are not uncommon. Once infected, it is often difficult to recover, and Gram-negative bacillary enteritis, sepsis, or urinary tract infection is often difficult to cure.

　　1. Malnutrition:The small stomach syndrome causes patients to be in a semi-starvation state for a long time after eating, and dumping syndrome and poor gastrointestinal absorption lead to weight loss and malnutrition.

　　2. Anemia:Due to the decreased gastric acid after surgery, the absorption of iron is affected, leading to iron deficiency anemia. Due to the lack of antianemia intrinsic factor after gastrectomy, the absorption of vitamin B12 is impaired, leading to megaloblastic anemia.

　　3. Diarrhea:It is mainly due to the rapid emptying of the stomach after the Billroth II anastomosis, increased peristalsis of the small intestine, poor digestion and absorption. In addition, the food and bile, and pancreatic juice cannot be well mixed, losing the emulsifying fat function of pancreatic juice decomposition and bile salts, affecting fat absorption, leading to steatorrhea.

　　4. Bone disease:It usually occurs 5 to 10 years after surgery, with bone softening being more common, and severe cases can lead to osteoporosis. The main symptoms include bone pain, weakness of the lower limbs, and an increased risk of fractures. After the Billroth II procedure, food no longer passes through the duodenum, resulting in reduced calcium absorption. Poor fat absorption also affects the absorption of fat-soluble vitamin D.

　　1. High-protein and high-calorie:High-protein, high-calorie, low-fat semi-liquid diet or soft food, with protein over 100g/d and less than 40g/d of fat, a total caloric intake of 10.46MJ (2500kcal). Choose foods with low fat content and easy to digest, such as fish, chicken, egg whites, tofu, and skimmed milk. It is not advisable to consume too much vegetable oil. Severe diarrhea patients can be given medium-chain fatty acids. Severe cases can adopt intravenous hyperalimentation or elemental diet and emulsified diet to ensure energy and positive nitrogen balance;

　　2. Supplement sufficient vitamins:In addition to food supplementation, injection supplementation is necessary when required. According to clinical symptoms, focus on supplementing the corresponding vitamins, such as vitamin A, complex vitamin B, vitamin C, vitamin D, and vitamin K, etc.;

　　3. Pay attention to electrolyte balance:Especially during severe diarrhea, it is extremely important to supplement electrolytes, which can be administered intravenously in the early stage. Fresh fruit juice, oil-free meat soup, mushroom soup, and other foods can be provided in the diet. People with iron deficiency anemia can eat iron-rich foods such as animal liver, and iron supplements can be taken orally if necessary;

　　4. Eat small, frequent meals:Choose fine, soft, and easy-to-digest foods to ensure sufficient nutrition without increasing the burden on the intestines. Pay attention to cooking methods, and it is best to use boiling, stewing, roasting, and steaming, avoiding frying, frying, and stir-frying to reduce the amount of fat provided.

　　5. Gluten-free diet:Celiac disease patients should strictly and long-termly follow a gluten-free diet and avoid drinking beer. Gluten-free diet treatment for 1 to 2 weeks can usually show efficacy.

　　First, blood routine:

　　The total amount of hemoglobin in the blood decreases due to anemia.

　　Second, small intestinal absorption function test:

　　1. Determination of fat globules, nitrogen content, muscle fibers, and糜蛋白酶content in feces: When fat globules are more than 100 under high-power microscopic vision ( Sudan III staining), malabsorption of fat can be considered; when the nitrogen content in feces increases, malabsorption of carbohydrates can be considered; when muscle fibers increase and the content of糜蛋白酶decreases, all of these suggest malabsorption of the small intestine.

　　2. Dextrose absorption test: For patients with poor small intestinal absorption function, the excretion of D-xylose in the urine is often reduced.

　　3. Radioactive isotope labeled vitamin B12 absorption test (Schilling test): For patients with impaired small intestinal absorption, the concentration of radioactive isotopes in the urine is significantly lower than normal.

　　Upper gastrointestinal barium meal, barium enema, and gastrointestinal endoscopy should be performed.

　　Dietary adjustment is of great importance for improving the symptoms such as diarrhea, abdominal pain, weight loss, anemia, and systemic malnutrition in patients with poor digestion and absorption, and for promoting the recovery of patients.

　　1. Provide sufficient calories and protein.Due to the long-term chronic course, the body consumes a lot, and sufficient calories should be provided to prevent further weight loss. High-protein, high-calorie, low-fat semi-liquid or soft rice diets can be provided, with more than 100 grams of protein per day, 40 grams of fat per day, and a total caloric intake of 10,460 megajoules per day (2,500 kcal per day). Choose foods with low fat content and easy to digest. For severe cases, intravenous hyperalimentation or elemental diet and blended diet can be adopted to ensure caloric and positive nitrogen balance.

　　2. Supplement sufficient vitamins.In addition to food supplementation, vitamin preparations may be needed if necessary. Based on clinical symptoms, focus on supplementing the corresponding vitamins, such as vitamin A, vitamin B complex, vitamin C, vitamin D, and vitamin K.

　　3. Pay attention to electrolyte balance.During severe diarrhea, the supplementation of electrolytes is extremely important, and early intravenous supplementation can be considered. Fresh fruit juice, oil-free meat soup, mushroom soup, and other foods should be provided in the diet. People with iron deficiency anemia can eat iron-rich foods such as animal liver, and iron supplements can be taken orally if necessary.

　　4. Eat small, frequent meals.Choose foods that are fine, soft, and easy to digest to ensure sufficient nutrition without increasing the burden on the intestines. In cooking, try to make the food fine,碎, and soft, and it is best to use methods such as boiling, stewing, roasting, and steaming, avoiding deep-frying, frying, and stir-frying to reduce the amount of fat provided. Pay attention to the color, smell, taste, and shape of the food, and try to increase the patient's appetite. It is best to have 6 to 7 meals a day.

　　5. To ensure nutritional supply, substitute therapy can be used for patients with decreased appetite.Oral elemental diet, total nutrition preparation, etc., to supplement nutrition.

　　I. Treatment

　　1. Drug Treatment

　　(1) Antibiotic application:

　　① Amoxicillin/clavulanate potassium (Amoxiclav) each tablet contains 250mg amoxicillin and 125mg clavulanate potassium, use 1-2 tablets, 3 times a day, which can effectively control aerobic and anaerobic flora and correct malabsorption.

　　② Cefaclor: Oral 250mg, 4 times a day.

　　③ Metronidazole (Flagyl): 250mg, 3 times a day.

　　(2) Vitamin supplementation: supplement vitamins B12, A, D, E, K.

　　(3) Supplement and correct relative insufficiency of pancreatic function with pancreatic enzyme preparations.

　　2. Surgical Treatment

　　Indications for surgery: including input loop syndrome, jejunoileal colonic fistula, malrotation of stomach and jejunum, and malabsorption after gastric resection without special cause, for whom drug treatment is ineffective. Selection of surgical methods:

　　(1) It has been proven that changing BillrothⅡ to BillrothⅠ corrects the loss of fecal fat, malabsorption of vitamin B12, and the proliferation of bacteria in the small intestinal lumen.

　　(2) An intestinal segment is interposed between the antrum and duodenum to restore the antrum-duodenal channel. Experimental evidence shows that the amount of fecal fat excretion in patients after interposed jejunal surgery is significantly lower than that after conventional gastric resection and antrum-duodenal or jejunoileal anastomosis; compared with conventional gastric resection, the weight of patients after gastric resection and interposed jejunal surgery increases.

　　II. Prognosis

　　After the above internal medicine treatment, the condition of most patients has improved significantly. If there are complications such as input loop syndrome, jejunoileal colonic fistula, etc., reoperation can be considered to change BillrothⅡ to BillrothⅠ.