Soli - you have to use bag after the surgery since the whole point of catheter after RP is to make sure that urine drains constantly without any delay. There should be no strain on your bladder since your urethra was cut off and than reattached to your bladder. There will be a lot of blood in your initial urine and possibly some small cloths also. All of that junk needs to drain, drain , drain. This gentlemen was kind enough to explain his way of dealing with catheter placement and attachment. The rest does not apply for RP.