Hard left side of the belly button will not move there may be non-disease causes and disease causes. 1. Common non-disease causes: (1) Poor bowel movement: if the patient has poor bowel movement and prolonged failure to relieve bowel movement tends to cause feces to collect in the sigmoid colon, a mass can be felt in the left lower abdomen. (2) Full bladder: Holding urine leads to a full bladder, and a mass can be felt in the center of the lower abdomen. (3) Thin stature: people who look thin are more likely to palpate physiologic abdominal masses such as the sigmoid colon, abdominal aorta, and bony structures due to less subcutaneous fat. 2. Common causes of disease: mostly due to inflammation, tumor, tuberculosis, obstruction, immunity, etc. It can also be due to congenital factors, such as congenital renal cysts, renal ptosis, ectopic kidneys, wandering kidneys, mesenteric cysts and so on. There are more causes of abdominal masses, and only important or common causes are listed above. For non-disease causes, no special treatment is often needed; while for possible disease causes, timely medical consultation is needed for early diagnosis.