Anatomically speaking, the organs of the left upper abdominal mass mainly include the stomach, the colonic splenic flexure, the tail of the pancreatic body, the spleen, and the left kidney. Clinically, the common diseases include five major categories: first, diseases of the stomach, including benign and malignant diseases of the stomach, which usually require further gastroscopy and even surgery if necessary. Second, common diseases are mainly pancreatic tail, mainly due to acute and chronic pancreatitis or malignant tumors of the pancreatic tail, which usually require CT examinations of the liver, gallbladder, pancreas and spleen, and if necessary, surgical treatment, and conservative treatment mainly using acid and enzyme suppression therapy. Thirdly, splenic diseases mainly include splenic hemangioma, splenic cyst or hypersplenism caused by portal hypertension, which usually require CT examination of liver, bile and pancreas and spleen, and if necessary, splenectomy. Fourth, the disease of colonic splenic flexure is mainly due to incomplete or complete intestinal obstruction caused by colonic tumor or polyps, which usually requires colonoscopy and surgery if necessary. Fifth, mainly kidney disease, especially left-sided kidney disease, usually stones or tumors, further urological ultrasound examination or CT examination of the kidney is needed, and surgery is performed if necessary.