The aim of our observational study was to determine whether cystocele type varies between vaginally parous and vaginally nulliparous women in order to gain insights into the etiology of cystocele.

This is a retrospective analysis of 464 vaginally nulliparous women seen routinely at two tertiary urogynecology centers between November 2006 and November 2019. Our control group consisted of 872 vaginally parous women who had visited our unit between July 2017 and November 2019. All patients underwent a standardized interview, clinical examination, uroflowmetry, multichannel urodynamic testing and 3D/4D translabial ultrasound. On imaging, a significant cystocele was defined as a bladder descent to 10mm or more below the symphysis pubis. Volume datasets were retrieved and analyzed offline by the first author, blinded against all clinical data. Statistical analysis was carried out with SAS version 9.4 (Cary, USA).

Of 5266 women seen during the inclusion period, 464 were vaginally nulliparous. Three datasets were excluded because of missing volumes. Out of 872 vaginally parous women, one patient was excluded due to missing volumes. Compared to vaginally parous women, vaginally nulliparous women presented at a younger age, 58 compared to 49 years respectively (p < 0.0001). 104 vaginally nulliparous (22.4%) and 489 vaginally parous women (56.1%) presented with symptoms of prolapse (p < 0.0001). 306 vaginally nulliparous (66.1%) and 648 parous women (74.3%) presented with symptoms of urinary stress incontinence (SUI) (p < 0.002). Mean bladder descent on ultrasound was significantly different between vaginally nulliparous and parous women with 11mm above and 8mm below symphysis pubis, respectively (p < 0.0001). Of 461 vaginally nulliparous women, 43 (9.3%) had a significant cystocele on ultrasound, with 23 (53.5%) being of Green type II and 20 (46.5%) Green type III. Out of 871 vaginally parous women, 418 (48.0%) had a significant cystocele on ultrasound, of whom 145 (34.7%) were Green type II and 273 (65.3%) Green type III cystocele (p < 0.0001). This significant difference was confirmed after excluding women with previous anterior repair and/or incontinence surgery.

Cystoceles were much more prevalent in vaginally parous women, but they do also occur in nulliparae. There are two distinct types of cystocele, classified on the basis of retrovesical angle (RVA) and the degree of urethral rotation (1). Cystourethrocele or Green type II cystocele has in the past been considered to be due to a lateral fascial defect, while Green type III cystocele was thought to be due to a central fascial defect. However, sonographic studies have not provided any support for this thesis. On the contrary, it has been demonstrated that Green type III cystocele is associated with avulsion injury of the levator ani muscle and hence more likely to be caused by birth-related trauma (2, 3). In vaginally nulliparous women, a Green type II cystocele was more prevalent while Green type III cystocele was more common in women who had given birth vaginally (p < 0.015). On testing for multiple confounders (age, BMI, asthma, smoking, heavy lifting and familial history of prolapse) on multivariate analysis, the difference in proportions of cystocele Green type II and III in vaginally nulliparous versus parous women remained significant (p < 0.0001).

Nulliparity was associated with a higher proportion of Green type II cystoceles. Green type III cystocele was more common in vaginally parous women. This suggest that Green type III cystocele may be more likely to be due to birth-related trauma to pelvic floor structures.

Green, T.H., Jr., Urinary stress incontinence: differential diagnosis, pathophysiology, and management. Am J Obstet Gynecol, 1975. 122(3): p. 368-400.
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Chantarasorn, V. and H.P. Dietz, Diagnosis of cystocele type by clinical examination and pelvic floor ultrasound. Ultrasound Obstet Gynecol, 2012. 39(6): p. 710-4.