Malabsorption syndrome is a syndrome caused by various causes of malabsorption of nutrients from the small intestine, which must undergo adequate digestion. Therefore, malabsorption syndrome in a broad sense includes dyspepsia and malabsorption, so it is also known as “digestive malabsorption syndrome”. Many diseases can cause this syndrome, but their clinical manifestations and laboratory findings are often similar, malabsorption includes a variety of nutrients, of which fat absorption disorders are the most characteristic. That malabsorption syndrome to do what auxiliary tests? 1, hematological examination: most of them are giant erythrocytic anemia, but also normocytic or mixed type (large cell low hemoglobin). Tropical stomatitis diarrhea is mostly megaloblastic anemia. Serum iron, potassium, calcium, sodium, and magnesium concentrations may be decreased. Serum carotene levels may be decreased. Plasma albumin, lipids, and prothrombin may be decreased. Prothrombin time may be prolonged. 2.Fecal lipid determination: (1) Qualitative test: can be observed by the naked eye first to check the presence of suspended fat droplets, and then examined under the microscope. Sudan III staining can be used. Patients with moderate and severe steatorrhea can be positive, while those with less than 6g of fecal fat per day are negative. (2) Quantitative test: The daily excretion of fecal fat does not exceed 6g, or 5% of the fat consumed, in normal people who enter a modified diet. The international use of intake and excretion balance test. The method is: eat a standard test meal containing 50-80g of fat for 4-5 days, and then keep the whole sample of stool for 3 days, and determine the amount of fecal fat daily by chemical methods, if the average daily amount of fecal fat exceeds 7g, it can be diagnosed as malabsorption of steatorrhea. This is a very reliable traditional standard method. In recent years, it has been proposed to use radioactive iodinated triglycerides to examine the intestinal absorption of neutral fat, but this method has some limitations because of the poor stability of the commercial 131I preparation. Recently, it has been suggested that the use of a stable non-radioactive factor 13C-trioctanoin can be used for the qualitative and quantitative determination of fat malabsorption, and the effect is better than 31I. 3, small intestine absorption function test: (1) α-xylose method: after oral administration of 25g α-xylose, urine was collected for 5 hours for quantitative analysis, and the normal excretion should be 5g or more. This method can be used as a census test for diffuse small bowel disease. (2) Radioisotope labeling test technique: For example, 131I albumin, 131IPVP (polyvinylpyrrolidone), 51 chromium albumin and 67 copper plasma copper cyanide are used to quantify protein absorption disorders. In addition,57 cobalt labeling is used to determine vitamin B12 absorption, and the Good Schilling test. Radioisotopes are also available to determine malabsorption of iron, calcium, amino acids, folic acid, pyridoxine, and vitamin D. 4.X-ray examination: including gastrointestinal examination and bone radiographs. It is reported that the positive rate of X-ray examination of malabsorption comprehensive film is generally up to 80%-90%. Gastrointestinal barium meal imaging can be seen in most of the small intestine with functional changes, with the jejunal segment being the most obvious. The main X-ray lesions are dilatation of the intestinal lumen, fluid accumulation and barium precipitation. The intestinal curvature is divided into snowflake distribution phenomenon, and the mucosal folds are thickened or the intestinal wall is smooth in a “wax tube” sign. The passage time of barium meal is delayed. Bone pain site radiographs can be seen with osteoporosis, osteochondrosis signs or pathological fractures. 5, small intestine mucosal biopsy: transoral route of small intestine mucosal biopsy, can be used in selective patients in the examination of malabsorption. This technique has greatly improved the understanding of the histopathological basis of malabsorption. 6, special examination of various primary diseases leading to malabsorption: such as liver function tests in patients with hepatitis and cirrhosis, amylase checks in patients with pancreatic diseases and blood glucose checks in patients with diabetes, etc.