On MR images, the hydrosalpinx appears as a fluid-filled tubular structure that arises from the upper lateral margin of the uterine fundus and is separate from the ipsilateral ovary. A dilated fallopian tube folds upon itself to form a sausagelike C- or S-shaped cystic mass as seen below
Sagittal T2-weighted MR image shows an S-shaped cystic mass (arrow) and partially effaced plicae (arrowhead), findings that help differentiate the hydrosalpinx from an ovarian cystadenoma.
Axial T2-weighted MR image shows an elongated cystic lesion with internal septa (arrows) in the left adnexa, a finding that mimics hydrosalpinx.
Sagittal T2-weighted MR image of the same patient clearly demonstrates the round mass (arrows) and complete intracystic septa, findings suggestive of an ovarian cystadenoma rather than hydrosalpinx.