A round hard lump in the right lower abdomen of a woman lying down can be caused by a variety of etiological factors, such as appendicitis, colon tumor, intestinal obstruction, ovarian tumor, congenital developmental anomalies caused by enlarged organs and organs displacement and so on. 1. Colon tumor: when there is a tumor in the ascending colon, palpation of the abdominal wall may reveal a round hard mass in the right lower abdomen. Benign tumor grows slowly and is usually not accompanied by other systemic symptoms. Malignant mass grows faster, and there may be symptoms such as loss of appetite, emaciation, anemia and so on. 2. Intestinal obstruction: when there is intestinal obstruction in the right lower abdomen, part of the intestinal tube is dilated, the surface tension is increased, and a round mass can be touched in the abdomen. Clinically, it can be considered as intestinal obstruction when it is accompanied by vomiting and abdominal cramps, and the anus stops defecation. 3. Pelvic tumor: female pelvic tumors, such as ovarian cancer, ovarian cysts, teratoma, etc., can be detected as round hard lumps on the abdominal wall during physical examination. 4. Ectopic pregnancy: when ectopic pregnancy is located in the right lower abdomen, a round mass can be detected in the right lower abdomen. 5. Displacement of organs due to congenital developmental anomalies will gradually appear with growth and development, such as spleen, kidney, etc., which can be detected from childhood. If you find a round lump in the right lower abdomen, you should pay attention to it and go to the local hospital in time, complete the examination, make a clear diagnosis and follow the doctor’s instructions.