Thirty patients who underwent radical cystectomy and bladder substitution and thirty people with native bladders will be enrolled in the study. After meticulous explanations each person will undergo sterile catheterization of the bladder/neobladder with a 14 Fr Foley catheter. After catheterization the bladder will be fully emptied. Randomly assigned volume of sterile saline will be injected to the bladder via the catheter by one sub investigator and the bladder capacity will be measured via a portable ultrasound scanner for non-invasive bladder volume measurement (BladderScan BVI3000) by another sub investigator. The volume injected and the measured results will remain in a closed envelope till the completion of the trial. After each measurement the first sub investigator will completely empty the bladder/neobladder and the process will repeat itself for a total of six measurements for each patient or first mention of discomfort (whichever comes first), after which the bladder will be drained once more and the catheter removed.

Inclusion Criteria:

Group A: Patients ages 18-75, at least 6 month after radical cystectomy and bladder substituition Group B: Volunteers same age group as group A, with native bladder as control group

Exclusion Criteria:

Group A: carrying ureteral stent of any kind, inability to catheterize patient due to severe urethral stricture, incarcerated post operative ventral hernia, after mesh repair of POVH, active urinary tract infection, acute bacterial prostatitis.

Group B: patients after partial cystectomy, incarcerated post operative ventral hernia, after mesh repair of POVH, active urinary tract infection, acute bacterial prostatitis.