Lying flat on the left side of the navel occasionally pressed with a hard lump with pain may be due to intra-abdominal tumors, hernia, feces and so on. 1. Intra-abdominal tumor: when the tumor or cyst is large, it can contact the intestinal tumor on the body surface, such as female pelvic cyst. When lying down, there is a hard lump with pain on the left side of the navel when pressed, usually, colonoscopy and imaging are needed. 2. Hernia: due to various causes of increased intra-abdominal pressure, the intestinal tube and omentum can protrude from the thinner part of the abdomen. A lump can be felt on the left side of the belly button, and there will be pain when pressed. This lump will change with the increase of intra-abdominal pressure. 3. Feces: People who have been constipated for a long time and do not defecate for a long time, the stool will accumulate in the intestines and form a lump, which is hard on the surface of the body and there will be pain when pressed. The hard lumps will disappear on their own after a bowel movement. When found lying down, press the left side of the navel with hard lumps with pain, there may also be other reasons, it is recommended to seek medical attention in a timely manner, to clarify the cause and treatment, to avoid delays in the condition.