Sudden stomach pain can be caused by many reasons, which can be seen in diseases of the digestive system, diseases of the urinary system, gynecological diseases and so on. 1. Diseases of the digestive system: acute and chronic gastritis, peptic ulcer, irritable bowel syndrome, appendicitis, cholecystitis, gallbladder stones, pancreatitis, intestinal obstruction and so on. 2. Diseases of the urinary system: stones in the urinary system, including urethral stones, bladder stones, ureteral stones, kidney stones and so on. Most of them are colic, and some of them will have symptoms such as urinary urgency, urinary pain and hematuria. 3. Gynecological diseases: women with sudden stomach pain should also consider acute pelvic inflammatory disease, acute attack of chronic pelvic inflammatory disease, adnexitis, cervicitis, ectopic pregnancy, ovarian cyst torsion and so on. The causes of sudden stomach pain are complex, and you should seek medical attention in a timely manner for examination and treatment under the guidance of a doctor.