Pelvic ultrasound and TVS are different approaches
An abdominal pelvic ultrasound views pelvic organs through the lower abdomen and commonly requires a comfortably full bladder. Transvaginal sonography provides closer pelvic detail using a different approach and preparation.
TVS is performed only when clinically appropriate, explained and consented. The requested method depends on symptoms, age, history and the question asked by the referring clinician.