Sudden back pain can be caused by the following reasons: 1. lumbar sprain, when the lumbar acute sprain can have acute muscle injury resulting in sudden back pain, which should be diagnosed with the history of trauma and related investigations. 2. kidney disease, when a kidney tumor ruptures, sudden back pain can occur. 3. stones, when a kidney stone travels downward and gets stuck in the ureteral stenosis, sudden back pain can occur, often accompanied by reflex pain in the abdomen and hematuria. 4. 4. Blockage of blood vessels, such as thrombosis or embolism of the renal artery, can cause sudden back pain, often tearing pain, and the patient should check the ultrasound and angiography of the urinary system for diagnosis. 5. Gallbladder disease, when the right side of the back pain, can be considered as a sudden back pain caused by gallbladder stones or rupture of the gallbladder. In this case, ultrasound, CT and angiography of the gallbladder should be performed to diagnose.