Pain in the lower abdomen is usually considered appendicitis. A lesion of the appendix can cause pain in the lower middle or right side of the abdomen. In particular, the pain in the lower right abdomen is very pronounced and is accompanied by tenderness and localized muscle tension, especially when standing up, which can be exacerbated by exertion of the abdominal muscles. Blood tests and ultrasound examination of the appendix can be performed to further clarify the situation. If the pain is caused by appendicitis, appendectomy is required. It is also possible to have colon lesions, such as colon tumors, which can lead to pain in the lower abdomen, usually accompanied by symptoms such as loose stools, increased frequency of stools, and bloody stools. If necessary, colonoscopy and abdominal CT can be done, and if it can be diagnosed that the abdominal pain is caused by colon cancer, radical tumor surgery is recommended.