Fat malabsorption, also known as steatorrhea, is a syndrome due to maldigestion and malabsorption of fat and can be seen in a variety of diseases such as pancreatic, hepatic, biliary, and intestinal disorders. Steatorrhea is a syndrome caused by malabsorption of fat and is seen in a variety of diseases such as pancreatic, hepatic, biliary and intestinal diseases. Pediatric fat malabsorption examination items 1, microscopic examination of fecal fat (1) Sudan Ⅲ staining microscopy: the feces on a slide, add a few drops of 95% ethanol mixed with Sudan Ⅲ saturated ethanol (95%) solution staining, microscopic neutral fat was yellow or orange round ball. In addition, put the feces on the slide, add a few drops of 36% acetic acid and Sudan III solution, mix thoroughly to cover the slide, put on the alcohol lamp and gently heated until boiling, after cooling and microscopic examination, the fatty acids can be stained into orange-yellow spheres. Microscopic fat globules are more, such as more than 6 per low-power field of view, often suggesting excessive fecal fat. This method is simple, but the sensitivity is poor, moderate or severe steatorrhea is positive. (2) Take 1 drop of saline and 1 drop of saturated ethanol solution of scarlet dye, add a small amount of feces on a slide and mix well, cover with a cover glass and examine, you can see round bubble-shaped neutral fat and crystalline fatty acids. If more than 1/4 of the specimen is stained red, the test is strongly positive (or), for severe steatorrhea. 2, iodine oil tolerance test to the child oral iodine oil (poppy seed oil with hydriodic acid, so that the iodine content of 40%) iodine and vegetable oils in the unsaturated fatty acids are tightly bound to the digestive tract to be absorbed before dissociation, from the urinary excretion, 12 ~ 18h after the service to collect the urine, 7 test tubes for the urine of the times diluted, each tube of 0.5 ml, each with 3 drops of newly formulated 1% starch suspension as a semi-quantitative iodine test. If the 4th tube (1:8 dilution) or above shows blue color, it is positive, indicating that the digestive tract fat absorption is normal. Avoid using it if you have a history of iodine allergy. 3, serum carotene determination carotene is the precursor of vitamin A, serum carotene content can indirectly reflect the fat absorption. Under normal dietary conditions, the normal value of serum β-carotene is: infants 0.37 ~ 1.3 μmol / L (20 ~ 70 μg / dl); children 0.74 ~ 2.42 μmol / L (40 ~ 130 μg / dl). In mild steatorrhea this lipochrome that is not easily absorbed, such as dietary carrots or other carotenoid-rich foods for days, such as significantly lower, can be considered to exist fat malabsorption. Fat malabsorption is often reduced to 1 to 2 μg/L, and this result is not affected by the amount of vitamin A intake. However, false negatives can be seen in children who consume more green and yellow vegetables and fruits, while false positives can be seen in children who do not consume such foods, such as infants under 8 months of age. 4. Determination of the fecal fat theorem and calculation of the fat absorption rate If the simple methods mentioned above fail to solve the problem, the fat content of food and feces can be measured and the absorption coefficient can be calculated. The child consumes a normal diet containing a certain amount of fat every day, and the fat calories account for at least 35% of the total calories for 5 days, and then collects all the feces every day for the last 3 days for the fecal fat quantitative determination, and calculates the fat absorption rate: Fat absorption coefficient=[total fat intake (g)-total fat discharged (g)]/total fat intake (g)×100% Normal preterm infants have an absorption rate of 60% to 75%; term infants have an absorption rate of 80% to 85%; infants with 1 year old can be false positive. The absorption rate in normal preterm infants is 60% to 75%; in term infants, 80% to 85%; and in normal infants over 1 year of age, the coefficient is 95% or higher. Significantly low absorption is diagnostic of fat malabsorption. Although this test is more accurate, but the operation process is complicated, smaller children often have difficulties in collecting feces, Sudan Ⅲ staining microscopy and serum carotene determination screening methods can be used. 5.Blood test Peripheral blood smear can detect whether there is small cell hypochromic or macrocytic anemia. Echinococcus should be considered as β-lipoproteinemia, in which serum cholesterol and triacylglycerol are low, and several β-lipoproteins are absent.Shwachman-Diamond syndrome has a decrease in peripheral blood granulocytes. 6.N-benzoyl-L tyrosine-p-carbamic acid BT-PABA test is a reliable and simple method to diagnose pancreatic exocrine function. The principle is that the chymotrypsin in pancreatic secretion can hydrolyze the amino acid peptide bond of BT-PABA, and the PABA will remain in the intestinal lumen as a marker and be absorbed into the blood circulation. It is excreted in the urine. PABA levels in both blood and urine decrease when pancreatic secretion is reduced. In order to avoid false positives, 3 days before the test, avoid fruits and sulfonamide, chloramphenicol, diuretics, traditional Chinese medicine, fasting BT-PABA 250mg, 2h after taking venous blood or stay 6h urine, determination of PABA content, obviously low. It is suggested that the pancreatic exocrine function is low. 7, dextrose absorption and excretion test sugar is a pentose sugar, orally absorbed by the jejunum, not metabolized in vivo, by the urinary excretion, in the normal conditions of renal function, xylose absorption and excretion of the amount to reflect the absorption function of the small intestine. Oral xylose 14.5g/m2, maximum not more than 25g, 1h after measuring xylose blood concentration, normal>25mg/dl; can also be oral xylose 1g (10% solution), followed by drinking water l00 ~ 200ml, collect 5h urine xylose, normal discharge>0.25g. If blood or urine xylose significantly reduced, suggesting that there is a wider range of damage to the jejunum mucosa, and it can be indirectly deduced that the fat malabsorption is caused by the damage to the intestinal mucosa. It can be indirectly inferred that fat malabsorption is due to intestinal mucosal damage, and has nothing to do with simple pancreatic exocrine or bile salt deficiency. 8.Vitamin B12 absorption test Schilling test. Vitamin B12 and internal factor binding, by the end of the ileum is absorbed, the body of vitamin B12 storage saturation, excess B12 that is discharged from the urine. During the test, sufficient amount of vitamin B12 is injected intramuscularly to saturate the body’s storage. And then oral nuclide 60 cobalt (60Co) labeled vitamin B12 trace, leave 24h urine measurement of nuclide vitamin B12 excretion, such as excretion is less than 5% of the intake, such as the sick children do not have internal factor deficiency, suggesting that the ileum mucosa has a wide range of injuries, including surgical resection. Intestinal bile salts are reduced by bacteria to deoxycholic acid or lithocholic acid, most of which is reabsorbed by the terminal ileum, and can be reabsorbed into the intestine via the bile ducts after hepatic processing to aid in fat absorption. When there is extensive damage to the end of the ileum, it often suggests a decrease in bile salt absorption and bile salt pool, and fat malabsorption may be related to bile salt deficiency. 9.Duodenal drainage fluid examination can directly determine the content of bile acid, pancreatic lipase and trypsin. Microscopic examination of the drainage fluid of Giardia infection can find trophozoites. Bacterial culture colony count helps to diagnose bacterial overgrowth in the upper part of the small intestine. 10, small intestinal mucosal biopsy can be inserted into the intestinal biopsy catheter through the endoscope or through the mouth to take the small intestinal mucosa biopsy, can directly observe the mucosal lesions, for the diagnosis of celiac disease, no β-lipoproteinemia, enteropathic limb dermatitis, intestinal lymphatic dilatation, milk or soy protein allergy, tropical stomatitis diarrhea and giardia, etc. are helpful. In addition, biopsy specimens can measure the activity of disaccharidase, fat malabsorption with decreased disaccharidase activity often suggests that the mucosal lesions of the small intestine are more extensive. Ultrasound, electrocardiogram and X-rays are routinely done to aid in diagnosis and differential diagnosis. For example, abdominal ultrasound can detect the pancreas and biliary tract for anatomical abnormalities. Pancreatic fibrocystic degeneration is a common cause of steatorrhea abroad, which has not yet been reported domestically, and this disease is measured by the increased sodium chloride content of sweat.