Does bacterial vaginosis cause pelvic inflammatory disease if its undetected or untreated? there seems to be a lot of unclear information about this online.

No: PID is triggered by a set of germs best known as sexually transmitted diseases. Chlamydia & gonorrhea are the most often identified, though a few others are seen but rare. The moist protein/glucose rich mucous of the female genital tract attracts many stray germs that trigger this localized process. It does not traverse the cervix into the uterus & tubes to extend into the pelvis.