Descent and hypermobility of the rectum in women with obstructed defecation symptoms

Obstructed defecation symptoms (ODS) are common in women; however, the key underlying anatomic factors remain poorly understood. We investigated rectal mobility and support defects in women with and without ODS using pelvic floor ultrasound and MR defecography. This prospective case-control study categorized subjects based on questions 7, 8 and 14 on the PFDI-20, which asks about obstructed defecation symptoms. All subjects underwent an interview, examination and pelvic floor ultrasound, and a subset of 16 subjects underwent MR defecography. The cul de sac-to-anorectal junction distance at rest and during maximum strain was measured on ultrasound and MRI images. The ‘compression ratio’ was calculated by dividing the change in rectovaginal septum length by its rest length to quantify rectal folding and hypermobility during dynamic imaging and to correlate with ODS. Sixty-two women were recruited, 32 cases and 30 controls. There were no statistically significant differences in age, parity, BMI or stage of rectocele between groups. A threshold analysis indicated the risk of ODS was 32 times greater (OR 32.5, 95% CI 4.8–217.1, p = 0.0003) among women with a high compression ratio (≥ 14) compared with those with a low compression ratio (< 14) after controlling for age, BMI, parity, stool type and BM frequency. Female ODS are associated with distinct alterations in rectal mobility and support that can be clearly observed on dynamic ultrasound. The defects in rectal support were quantifiable using a compression ratio metric, and these defects strongly predicted the likelihood of symptoms; interestingly, the presence or degree of rectocele defects played no role. These findings may provide new insight into the anatomic factors underlying female ODS.