Anterior vaginal wall length and degree of anterior compartment prolapse seen on dynamic MRI

Abstract

The objective of the study was to determine the relationship between midsagittal vaginal wall geometric parameters and the degree of anterior vaginal prolapse. We have previously presented data indicating that about half of anterior wall descent can be explained by the degree of apical descent present (Summers et al., Am J Obstet Gynecol, 194:1438-1443, 2006). This led us to examine whether other midsagittal vaginal geometric parameters are associated with anterior wall descent. Magnetic resonance (MR) scans of 145 women from the prior study were suitable for analysis after eight were excluded because of inadequate visibility of the anterior vaginal wall. Subjects had been selected from a study of pelvic organ prolapse that included women with and without prolapse. All patients underwent supine dynamic MR scans in the midsagittal plane. Anterior vaginal wall length, location of distal vaginal wall point, and the area under the midsagittal profile of the anterior vaginal wall were measured during maximal Valsalva. A linear regression model was used to examine how much of the variance in cystocele size could be explained by these vaginal parameters. When both apical descent and vaginal length were considered in the linear regression model, 77% (R (2) = 0.77, p < 0.001) of the variation in anterior wall descent was explained. Distal vaginal point and a measure anterior wall shape, the area under the profile of the anterior vaginal wall, added little to the model. Increasing vaginal length was positively correlated with greater degrees of anterior vaginal prolapse during maximal Valsalva (R (2) = 0.30, p < 0.01) determining 30% of the variation in anterior wall decent. Greater degrees of anterior vaginal prolapse are associated with a longer vaginal wall. Linear regression modeling suggests that 77% of anterior wall descent can be explained by apical descent and midsagittal anterior vaginal wall length.

Fig. 1

MR image at maximal Valsalva showing anterior vaginal wall tracing (solid black line), distal vaginal wall (x), bladder location (triangle), cervical os location (circle), and coordinate system (dotted lines)

Fig. 2

Area under the anterior vaginal wall profile. Pubic bone, sacrum, and coccyx are traced. The anterior vaginal wall tracings are shown. A line (small dotted) is used to connect the two ends of the vaginal wall tracing to create an area (shown in gray). Examples aligned using horizontal large dotted reference line. a Minimal descent of most caudal bladder point (triangle). b Greater descent of the bladder point with longer vaginal wall length and larger area. c Similar vaginal wall length to B but smaller area and lesser descent of bladder point

Fig. 3

Vaginal length during Valsalva and distance of the most caudal bladder point below normal. There is a linear correlation y=0.69x−0.85, R²=0.30

Fig. 4

Subject examples showing relationship between apical support and vaginal length in determining the size of cystoceles. Top row:MR image with maximal Valsalva. Bottom row: Coordinate axis, vaginal tracings, as well as bladder and cervical locations. Images have been standardized for pelvic size and orientation. a Subject who had uterine descent and large cystocele. b Subject with relatively well-supported apical compartments who had large cystocele with a long anterior vaginal wall. c Subject with cystocele and a normal vaginal wall length. d Subject with cystocele with a short vaginal wall length