Left lower abdominal distension and pain, passing sour smelling stools may be caused by acute gastroenteritis, ulcerative colitis, irritable bowel syndrome, etc., and should seek medical attention promptly. 1. Acute gastroenteritis: If the patient has left lower abdominal distension and pain, sour stool, accompanied by vomiting, diarrhea and other symptoms, acute gastroenteritis should be considered. 2. Ulcerative colitis: it is a chronic non-specific intestinal disease, patients will have symptoms such as left lower abdominal distension and pain, sour and smelly stools, mucus, pus and blood stools. 3. Irritable bowel syndrome: a common functional gastrointestinal disease, patients will have symptoms such as left lower abdominal distension, sour smelling stools, abdominal discomfort. The above medications should be taken under the guidance of a medical professional. It is recommended to consult a doctor in time for the above symptoms, and treat them as early as possible under the guidance of a professional doctor to avoid delaying the condition.