Distension and pain in the left side of the small abdomen with a distinct sensation of falling is most commonly caused by intestinal infections, especially gastroenteritis, which can also present with nausea, vomiting, and diarrhea. There is also ulcerative colitis, which occurs more often in young people and can also manifest as blood in the stool. For patients with perianal disease and hemorrhoids, there is also a feeling of lower abdominal cramping during the acute attack, as well as blood in the stool and unformed stools. You should pay attention to your diet and avoid irritating foods. For patients with ulcerative colitis, anti-inflammatory therapy should be systematically administered, caloric intake should be ensured, high-protein foods should be supplemented, regular fiberoptic colonoscopy should be performed, and repeated diarrhea can easily induce disorders of the internal environment. If necessary, intravenous fluid supplementation is also needed, and basic trace elements and vitamins are given.