Cystitis B ultrasound examination with urine retention? Why

Cystitis B-ultrasound examination is required to hold urine, because the urine in the bladder increased, so that the bladder can be filled up, so that when doing B-ultrasound can be very good to show the situation in the bladder. If the patient does not hold urine, bladder is empty, then when doing B-ultrasound can not be very good to show the situation in the bladder. Therefore, patients before doing B-ultrasound, should drink a lot of water, hold urine and then check, so the results of the examination is better.