Possible causes of inability to urinate: 1. Acute obstruction of the urinary tract, such as stones or inflammation will occur when the urethra is completely obstructed. Stones for suffering from urinary stones, after extracorporeal shock wave lithotripsy and drug discharge, etc., the stones enter the urethra and become embedded in a certain part, causing urethral blockage and suddenly unable to urinate. With the increase of tumor volume, it can lead to complete obstruction of urethra or bladder outlet obstruction, resulting in patients unable to urinate.