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Pelvic ultrasonography uses ultrasonography to image structures in the pelvis, including the reproductive organs and urinary bladder. The probe's position determines the acoustic path and which structures lie in view: transabdominal and transvaginal ultrasound approaches observe the region from different geometries. Returning echoes provide information about interfaces and motion, with the usual limitations of acoustic access through gas and bone.^[ref]

Transvaginal ultrasound is pelvic ultrasonography with an internal probe positioned in the vagina, close to pelvic structures such as the uterus and ovaries. This changes the imaging geometry and the intervening acoustic path. The measured signal is still an ultrasound echo; the probe's position supplies access to structures that can be harder to view along an external abdominal path.^[ref]