In general, the left lower abdomen is distended like there is something on top of it, which can be considered to be caused by improper diet, intestinal obstruction, ulcerative colitis and so on. 1. Improper diet: recent consumption of cold, greasy, spicy, stimulating, indigestible food, such as drinking a lot of alcohol, eating cold drinks, hot and spicy, etc., stimulate the gastrointestinal mucosa, causing intestinal gas, the appearance of lower left abdominal distension. In addition, hard-to-digest food remains in the intestinal lumen for a long time and produces gas by fermentation, which can also cause left lower abdominal distension. 2. Intestinal obstruction: the intestinal contents cannot pass through the intestines smoothly caused by intussusception, postoperative intestinal adhesions, intestinal torsion and other diets. It can be manifested as paroxysmal abdominal cramps, abdominal distension, loss of appetite, constipation, vomiting and so on. Among them, low intestinal obstruction and power abdominal distension are obvious, which can spread all over the abdomen; paralytic intestinal obstruction can have no obvious abdominal pain, but have the symptom of abdominal distension. 3. Ulcerative colitis: it is a chronic non-specific intestinal inflammatory disease, mainly involving the rectum and colon (body surface projection in the left lower abdomen), most of them are recurrent chronic course, which can be manifested as intermittent diarrhea, mucopurulent and bloody stools, abdominal pain, abdominal distension and so on. There are many other causes of left lower abdominal distension like something on top, such as urinary stones. It is recommended to consult a doctor in time to clarify the diagnosis and carry out targeted treatment.