Red Blood Cells (RBCs) in urine after a pelvic surgery like hysterectomy may result due to various reasons.
The patient after hysterectomy is kept on a draining catheter for couple of days. A foreign body like catheter may result in RBCs in urine for couple of weeks even in absence of infection.
A urinary infection following colonization of catheter with bacteria may result in bleeding with urine.
Bladder has to be dissected away from uterus during its removal. Handling of bladder or minor injuries to bladder during dissection may result in presence of blood in urine.
Even after a complete recovery, a fresh urinary infection is not uncommon in females, with presence of bacteria and RBCs in urine.
Your treating doctor would be able to reach the right conclusion and guide you after proper examination and necessary investigations.