Evaluating Z Scores to Quantify Levator Hiatal Distensibility by 3-Dimensional Ultrasonography in Nulliparas and Women With Pelvic Organ Prolapse.

OBJECTIVES

To use Z scores to quantify hiatal distensibility and to test the performance of Z scores for levator hiatal areas in predicting substantial pelvic organ prolapse (POP).

METHODS

We undertook a retrospective study of the data from 145 nulliparas and 166 patients with POP who had a clinical POP examination with 3-dimensional translabial ultrasonography. Z scores were used to normalize levator hiatal areas of nulliparas. The Z score model for the hiatal area was built by the formula Z score = (measured value - predicted mean value)/predicted standard deviation and was used to evaluate hiatal ballooning in women with POP.

RESULTS

Valid data were gathered from 134 nulliparas and 159 patients with POP. POP stage 1 was found in 46 women, stage 2 in 62, stage 3 in 43, and stage 4 in 8. We built the Z score model as follows: Z-Av = (measured value - 17.15)/3.11, where Av represented the minimal levator hiatal area on the maximum Valsalva maneuver. The levator hiatal area was strongly related to the POP stage (P < .001). On a receiver operating characteristic curve analysis, the cutoff of Z-Av was 1 for POP stage 2 or higher (sensitivity, 77%; specificity, 60%) and substantial POP on ultrasonography (sensitivity, 84%; specificity, 75%).

CONCLUSIONS

Hiatal distensibility can be exactly evaluated by Z-Av. A Z-Av value of less than 1.0 was defined as a "normal hiatal expansion," 1 to 3 as "mild ballooning," 3 to 5 as "moderate ballooning," 5 to 7 as "marked ballooning," and 7 or greater as "severe ballooning."