Small abdomen at night has been hidden pain, in the clinic is a relatively common class of symptoms, the causes include the following aspects: First, may be due to inflammation of the urinary system urethritis caused by infection, this situation is often accompanied by cystitis, abdominal pain and even urinary frequency, urinary urgency, the serious case will appear hematuria. Secondly, it may be caused by urinary stones, due to the stone in the ureter to discharge into the bladder process, resulting in spasmodic pain in the ureter, and the pain has been dispersed to the perineum to form a small abdominal distension and pain sensation, this situation usually have a clear history of kidney stones. Thirdly, it may be caused by pelvic inflammatory disease and tubal inflammation in women, and the chance of this situation is still relatively high. Therefore, if you have a vague pain in the abdomen, you should go to the hospital as soon as possible for a detailed examination to find the exact cause of the disease and carry out systematic and standardized treatment according to the cause of the disease.