pain in swelling in pelvic area

A family member of mine has had prostate cancer (16 years ago and 12 years ago).  His recent PSA test came back at 0 (yay!)...he had his bladder removed 2 years ago due to extreme radiation burning and damage to the bladder.  Had kidney failure once due to blockage (which made them finally do the bladder removal surgery).  Also when tests were being run 2 years ago they found a spot on his pancreas which he goes for tests every 6 months to keep an eye on it.  So far all is good and he's had excellent health for 2 years since bladder removal.  Now he has swelling in his pelvic region with pain.  They thought it was calcium build up as thats quite common with the surgery he had, but his one dr. doesn't think thats what it is.  He's also had a recent colonoscopy (routine-done yearly) and I believe the results of that were good as well.  Any idea whats causing the swelling and pain in his pelivic region? He has to see a kidney specialist and is going for a cat scan this week.