Kidney suddenly very painful, there are the following reasons: First, the most common cause is kidney stones. When the original fixed stone inside the kidney stone moves, there will be a sudden pain in the kidney, you can use antispasmodic and analgesic drugs to relieve the symptoms. Second, the common cause is renal artery embolism. Renal artery embolism refers to the arterial blood vessels of the kidney after the thrombosis of the kidney, resulting in insufficient blood supply to the kidney, resulting in necrosis, which requires examination, then anticoagulation and other treatments, and if necessary, interventional treatment. Thirdly, the sudden pain in the kidney may be related to urinary tract infection, especially acute pyelonephritis will lead to back pain symptoms are very obvious, need anti-infection treatment as well as advise patients to drink more water and urinate more often.