Comparison of dynamic magnetic resonance defaecography with rectal contrast and conventional defaecography for posterior pelvic floor compartment prolapse

Aim The study compared the diagnostic capabilities of dynamic magnetic resonance defecography (D-MRI) with conventional defecography (CD, reference standard) in patients with symptoms of prolapse of the posterior compartment of the pelvic floor. Method Forty-five consecutive patients underwent CD and D-MRI. Outcome measures were the presence or absence of rectocele, enterocele, intussusception, rectal prolapse and the descent of the anorectal junction on straining measured in millimetres. Cohen's Kappa, sensitivity, specificity, positive (PPV) and negative predictive value (NPV) and the positive and negative likelihood ratio of D-MRI were compared with CD. Cohen's Kappa and Pearson's correlation coefficient were calculated and regression analysis was performed to determine interobserver agreement. Results Forty-one patients were available for analysis. D-MRI underreported rectocele formation with a difference in prevalence (CD 77.8% vs. D-MRI 55.6%), mean protrusion (26.4 vs. 22.7 mm, p=0.039) and 11 false negative results, giving a low sensitivity of 0.62 and an NPV of 0.31. For the diagnosis of enterocele, D-MRI was inferior to CD with five false negative results, giving a low sensitivity of 0.17 and high specificity (1.0) and PPV (1.0). Nine false positive intussusceptions were seen on D-MRI with only two missed. Conclusion The diagnostic accuracy of D-MRI for diagnosing rectocele and enterocele is less than conventional defecography. D-MRI, however, appears superior to CD in identifying intussusception. D-MRI and CD are complementary imaging techniques in the evaluation of patients with symptoms of prolapse of the posterior compartment. This article is protected by copyright. All rights reserved.