What Causes Swelling In Penis In Kidney Dialysis Patients?

I have a family member who recently started at home kidney dialysis. Past medical history includes diabetes heart attack that resulted with a quadruple bypass, staph infection in which the sternum was removed, defibrillator and no spleen. Recently his penis is swolle, like a water balloon (possibly water retention). What may this be, or what may cause this? 69 yr old male 5'7 165lb is who this is in regards to