The place where the left hand crosses the waist usually refers to the left side of the mid-abdomen. The symptom of vague pain in the left side of the middle abdomen is common in ulcerative colitis, pancreatitis, endometritis and other diseases, should be timely consultation to identify the cause. 1, ulcerative colitis: rectum and sigmoid colon is the most common, the light can be no abdominal pain or only the left side of the lower and middle abdominal pain and other discomforts, the heavy can be sustained severe abdominal pain, can be accompanied by diarrhea, loss of appetite, nausea, fever and other manifestations. 2, pancreatitis: the pancreas is located in the mid-abdomen of the retroperitoneum, when the pancreas has inflammatory lesions, the patient may appear in the left mid-abdominal pain symptoms, mostly in the satiation of meals and drinking alcohol after the attack. 3, endometritis: belongs to one of the pelvic inflammatory diseases, preferably in sexually active women in their reproductive years, some patients may have no obvious symptoms or mild symptoms, mainly manifested in the lower and middle abdominal pain, pain, which can be aggravated by activities or after sexual intercourse. In severe cases, high fever, chills and headache may occur. In addition, dyspepsia, uterine fibroids, urinary system and other related diseases can also lead to vague pain in the left side of the mid-abdomen, it is recommended that the patient consult the doctor in a timely manner, improve the relevant examination, and if necessary, appropriate treatment.