Fatty diarrhea refers to a clinical syndrome group of nutrient deficiency caused by various causes of reduced digestion and absorption in the small intestine, resulting in incomplete absorption of nutrients and their excretion in the stool, also known as dyspepsia syndrome. Due to excessive fat excreted in the stool, it is also known as small intestine malabsorption, and is also called oleaginous diarrhea. Causes are common, such as malabsorption syndrome, bile salt and pancreatic digestive enzyme deficiency, small bowel inflammation or diverticulosis, intestinal-derived fat metabolism disorder, gastrinoma, or inability of celiac ducts to absorb fat. Typical steatorrhea stools are light in color, large in volume, greasy or foamy, often floating on the water surface, and mostly malodorous. 1, hepatobiliary disease More often seen in the biliary tract obstruction lesions of the extrahepatic bile duct obstruction, or intrahepatic bile duct obstruction, because the bile duct obstruction is most likely to cause bile retention, bile composition changes, resulting in a significant decrease in the concentration of bile acids in the intestinal cavity, thus affecting the digestion of fat hydrolysis and fatty acid decomposition, forcing fat from the stool, the occurrence of steatorrhea. 2, intestinal diseases various intestinal infections, extensive resection of the small intestine, primary small intestinal lymphoma, small intestinal ischemia caused by arteriosclerosis, intestinal lipid metabolism disorder syndrome, eosinophilic gastroenteritis, food allergies, etc., may damage the digestive function of small intestinal mucosal epithelial cells and occur steatorrhea. 3, pancreatic diseases chronic pancreatitis and pancreatic cancer in pancreatic lesions. This is mainly due to a significant decrease in pancreatic lipase secretion by the pancreas, resulting in poor fat digestion and causing a large amount of fatty substances to be excreted from the stool. 4, endocrine diseases Hyperaldosteronism, hypothyroidism, and even hyperthyroidism in a few endocrine diseases can also occur in steatorrhea. This is because endocrine disorders can easily trigger lipid metabolism disorders, and then steatorrhea occurs. 5.Other β-lipoproteinemia, γ-globulinemia, after most of the gastric resection, and scleroderma also tend to cause fat metabolism function to be reduced and steatorrhea occurs.