Comparison of High-Resolution Anorectal Manometry and Magnetic Resonance Defecography in Patients With Obstructive Defecation: Are Both Tests Necessary?

Introduction: Investigation of an evacuation disorder is often pursued in patients with symptoms of obstructive defecation. High-resolution anorectal manometry (HR-ARM) is a simple, safe, and widely available test to diagnose pelvic floor dysfunction. A more costly and less accessible test is magnetic resonance defecography (MRD). This study aims to quantify the added value of MRD in diagnosing pelvic floor disorders.

Methods: HR-ARM and MRD performed in patients with a diagnosis of constipation between January 1, 2020 and May 15, 2022 at Mayo Clinic were identified using Epic Slicer Dicer. Univariate and multivariate analyses were used to compare findings on MRD in patients with and without abnormal HR-ARM. Categorical variables were compared using the Pearson's chi-square test, and continuous variables were compared using the two-sample t-test.

Results: Seventy-six consecutive patients (81.8% female, 94.8% White, ages 19-82) who underwent both HR-ARM and MRD were included. The majority had evidence of dyssynergia on HR-ARM (n = 49, 64.5%). Patients with dyssynergia on HR-ARM were significantly more likely to have prolonged balloon expulsion at both > 60 and > 30 s (p < 0.001) and incomplete gel expulsion on MRD (p < 0.001). However, they were not more likely to have a clinically significant rectocele measuring > 2 cm (p = 0.17) or evidence of rectal prolapse (p = 0.07).

Discussion: Anatomic findings on MRD were similar between patients with and without evidence of dyssynergia identified by HR-ARM. In this retrospective review, simultaneously undergoing MRD in addition to HR-ARM does not appear to provide significant additional diagnostic information to guide therapeutic recommendations. Large prospective studies to evaluate the added value of MRD are needed.