Normal colonoscopy but hidden pain in the left side of the abdomen may be caused by gastrointestinal diseases, or gynecological diseases, reproductive system diseases or urinary system diseases. 1. Gynecological diseases: if it is a woman’s left-sided abdominal pain may be caused by gynecological diseases, such as pelvic inflammatory disease, adnexitis, cervicitis and so on. It is necessary to improve the ultrasound examination to further confirm the diagnosis. 2. Reproductive system diseases: if the left side of the male abdominal pain, colonoscopy results are normal, may be caused by prostatitis and other diseases. 3. Urinary system diseases: If there are kidney stones, urinary tract stones, urinary tract infections and other diseases, it may also lead to hidden pain in the left side of the abdomen. If the patient’s colonoscopy results are normal, the left side of the abdomen is still hidden pain, it is recommended to follow the doctor’s instructions to improve the other relevant examinations, under the guidance of a professional physician to identify the cause of the disease, and carry out appropriate treatment.