A distended sensation in the right lower abdomen may be appendicitis or appendiceal cancer. If it is appendicitis, it is an inflammatory disease, mainly caused by bacterial infection of the appendix, or it may be caused by obstruction of the appendiceal cavity. The early manifestation is vague pain in the upper abdomen or around the umbilicus, accompanied by nausea, vomiting and other gastrointestinal symptoms. The pain gradually shifts to the lower right abdomen and is more intense in nature, but sometimes the pain in the lower right abdomen is not very intense in the early stages of appendicitis. Blood tests are needed to detect elevated white blood cells, and abdominal ultrasound or CT can detect swelling of the appendix and oozing around the appendix. In the case of appendiceal cancer, the symptoms are not typical in the early stage, and the discomfort such as vague pain and distension in the right lower abdomen may appear. Sometimes CT abdomen can detect a mass in the appendix, but sometimes it can’t, so colonoscopy is needed to further clarify.