Bladder distension and pain with urine may be caused by cystitis, tumor, stone and other reasons. 1. Cystitis: it is the most common infectious disease in the urinary system. Inflammatory stimulation will cause the mucous membrane of the inner wall of the bladder to swell, and urine stimulation will cause swelling and pain, and most of them will be accompanied by frequent urination, urinary urgency, painful urination and other symptoms, which will lead to the phenomenon of distending and painful bladder when you have to urinate. 2. Tumor: benign tumors in the bladder or bladder cancer and other malignant tumors stimulation can also cause symptoms of bladder distension and pain when urinating. 3. Stones: Kidney stones, ureteral stones, and stones that fall into the bladder due to changes in the location of the stone may also lead to pain and distension of the bladder when urinating. There may be other reasons for bladder swelling and pain when urinating, so you need to go to the hospital in time for further examination to clarify the cause of the problem and follow the doctor’s instructions.