What could cause reactive lymph nodes in both inguinal regions (as noted on a ct scan)?

Reactive Lymph Nodes: It is very common to have reactive lymph nodes while fighting off an infection or post treatment inflammation. If you have not been tested or treated for a vaginal or bladder infection this may be a sign that you do need further testing or treatment.

Lots of things: A reactive lymph node is a pathology finding, that is something you can diagnose with a biopsy, but not with a ct scan. There are lots of lymph nodes in the inguinal region, and a few slightly enlarged nodes is not a big finding. If your doctor thinks more needs to be done, a biopsy might be needed.