The sudden very painful pain in the left abdomen is often caused by the following reasons: First, urinary stone impaction, when the kidney produces a stone, the stone may be discharged out of the body and reach the ureter. When it reaches the narrowing of the ureter, there will be strong pain, and at the same time it can be discharged to the left side of the back. It is necessary to go to the emergency department or the urology department of the hospital to improve the relevant examinations, such as blood routine, urological ultrasound and urinary routine. If the disease is considered, aggressive diuresis is needed, along with pain and antispasmodic medications. If there is no relief, lithotripsy or surgery is needed. Second, acute intestinal spasm, caused by eating too much spicy food or drinking alcohol. Third, caused by intestinal vascular lesions, such as mesenteric thrombosis.