Posterior vaginal prolapse is thought to cause difficult defecation and splinting for bowel movements. However, the temporal relationship between difficult defecation and prolapse is unknown. Does posterior vaginal prolapse lead to the development of defecation symptoms? Conversely, does difficult defecation lead to posterior prolapse? This prospective longitudinal study offered an opportunity to study these unanswered questions.

We sought to investigate the following questions: (1) Are symptoms of difficult defecation more likely to develop (and less likely to resolve) among women with posterior vaginal prolapse? (2) Is posterior vaginal prolapse more likely to develop among women who complain of difficult defecation?

In this longitudinal study, parous women were assessed annually for defecatory symptoms (Epidemiology of Prolapse and Incontinence Questionnaire) and pelvic organ support (POP-Q examination). The unit of analysis for this study was a visit-pair (2 sequential visits from any participant). We created logistic regression models for symptom onset among those women who were symptom-free at the index visit and for symptom resolution among those women who had symptoms at the index visit. To investigate the change in posterior vaginal support (assessed at point Bp) as a function of symptom status, we created a standard regression model that controlled for Bp at the index visit for each visit-pair.

We derived 3888 visit-pairs from 1223 women (each completed 2–7 annual visits). At the index visit, 1143 women (29%) reported difficulty with bowel movements, and 643 women (17%) reported splinting for bowel movements. Posterior vaginal prolapse (Bp≥0) was observed among 80 women (2%). Among those women without symptoms, posterior vaginal prolapse did not significantly increase the odds that defecatory symptoms would develop (difficult bowel movements, P=.378; splinting, P=.765). In contrast, among those with defecatory symptoms, posterior vaginal prolapse reduced the probability of symptom resolution (difficult bowel movements, P<.001; splinting, P=.162). The mean rate of change in posterior wall support was +0.13 cm. Among women without posterior vaginal prolapse, the presence of defecatory symptoms at the index visit did not have an effect on changes in Bp over time; however, among those with posterior vaginal prolapse (Bp≥0), defecatory symptoms were associated with more rapid worsening of posterior support (difficulty with bowel movements, P=.005; splinting, P=.057).

Posterior vaginal prolapse did not increase the odds that new defecatory symptoms would develop among asymptomatic women but did increase the probability that defecatory symptoms would persist over time. Furthermore, among those women with established posterior vaginal prolapse, defecatory symptoms were associated with more rapid worsening of posterior vaginal wall descent.