Main findings
In this study, the anatomical structures of the vagina were distinctly
displayed on MRI. A reference line that passes through the inferior
aspect of the pubic symphysis to the midpoint of the third sacral
vertebra was introduced and named PS3L. The marker points representing
the distal, middle, and apical points of the upper two-thirds of the
vagina showed relatively concentrated distributions along this line, and
the median distances from these points to the line were -0.5 cm, 0.0 cm,
and -0.2 cm. Additionally, the vaginal axis lay nearly parallel to this
line, and the median angle between the line and the vaginal axis was 0.0
degree. These trends were observed in all age subgroups, indicating that
the reference line PS3L approximates the axis of the normal upper
two-thirds of the vagina.