A piece of bulge on the left side of the abdomen may be physiological factors, or it may be a symptom of certain diseases, such as subcutaneous lipoma, colon cancer, etc., which should be promptly consulted to find out the cause. 1. Physiological factors: if some patients don’t defecate for a few days, feces accumulate in the intestinal lumen. One of the main functions of the colon is to absorb water. When the colon absorbs the water in the feces, the feces will be hard, and you may be able to feel the lumps. 2. Pathologic phenomena (1) Subcutaneous lipoma: Subcutaneous lipoma is a benign tumor that occurs in the subcutaneous tissue. Lipoma is mainly proliferation of fat cells, which often forms a kind of well-defined and soft fat mass, and may appear as a bulging piece on the left side of the stomach. (2) Colon cancer: the abdominal mass is mostly the tumor itself, the main body of the tumor protrudes into the intestinal lumen, coupled with the accumulation of feces in the intestinal lumen on the proximal side of the obstruction. Most of the lumps are hard and nodular. If the cancer penetrates and becomes infected, the fixed mass may cause a bulge on the left side of the abdomen. If a bulge is found on the left side of the abdomen, patients are advised to go to hospital for further examination.