BTDT so my situation may not mirror yours .... BUTT
I had a fever which would not come down and internal pelvic "aching" not really pain ... which would not stop
all starting about a week out from resection
I was back in hosp for a while after a pelvic abscess, post resection
I did have it drained and flushed with the interventional radiology dept
after I was re-admitted and put on IV antibiotics
later went home with a drain which I flushed at home ( I am a vet with lotsa' medical experience
and was treated as out patient until the drain came out with a follow up scan to show it had resolved.
Depends on your exact situation, BUTT be prepared for some more time in hospital
... just sayin'
they should do a culture on what they drain and get you on some heavy duty antibiotics
... = JMO 'cos ... BTDT
Best wishes and let us know if we can be of more support for you