Introduction and hypothesis: The perineal body is a fibromuscular pyramidal structure located between the vagina and the anus. It has been difficult to image because of its small size and anatomical location. This study used 2D transperineal ultrasound to measure the perineal body and assess whether there is an association with prolapse.
Methods: An observational, cross-sectional study was carried out in a tertiary level Urogynaecology department and included prolapse patients and healthy nulliparous volunteers (control group). This was a clinical assessment, including POP-Q and trans-perineal 2D ultrasound measurement of the perineal body height, length, perimeter, and area. Parametric tests were used, as the data were normally distributed. Results are reported as mean and 95% confidence interval (±95% CI).
Results: A total of 101 participants were recruited of which 22 were nulliparous healthy volunteers. Mean perineal body measurements in controls were height 22.5 ± 3.3 mm, length 17.4 ± 2.7 mm, perimeter 7.5 ± 0.9 mm, and area 2.8 ± 0.38 cm2. Perineal body measurements in 79 prolapse patients: height 16.9 ± 1.7 mm, length 16.0 ± 1.4 mm, perimeter 6.5 ± 0.5 mm and area 2.1 ± 0.5 cm2. A small perineal body was strongly associated with posterior compartment prolapse (paired t test, p < 0.0001) and wider POP-Q GH (paired t test, p = 0.0003). Surprisingly, Pelvic Organ Prolapse Quantification Perineal Body (POP-Q PB) of the two groups was not significantly different. A perineal body mid-sagittal area of less than 2.4 cm2 has been shown to be associated strongly with posterior compartment prolapse.
Conclusions: It is possible to measure the perineal body on 2D ultrasound. This technique facilitates the objective diagnosis of perineal deficiency. POP-Q PB does not predict the length or area of the perineal body.
Keywords: Perineal body; Perineum; Prolapse; Theory of prolapse.