If you want to urinate but can’t, then the possible causes: 1, urinary tract infection, can appear urethral mucosa congestion edema, resulting in increased bladder sensitivity, bladder storage of urine is not much, so frequent urination but not much urine or can not urinate, can also be because of urethral mucosa edema, urination can produce strong pain or irritation, so the patient can not urinate, need to carry out routine urine examination and urinary system B ultrasound examination is needed to confirm the diagnosis. 2. In the case of men, urinary retention may be caused by prostatic hyperplasia. If you have a prostate enlargement that causes obstruction of the urethral lumen, you may not be able to urinate in severe cases, and you may have a large amount of urine stored in your bladder, so you need to have a urinary ultrasound and residual urine examination to confirm the diagnosis. The urine cannot be discharged normally through the urethra. Urethroscopy and ultrasound measurement of residual urine are needed to confirm the diagnosis.