Comparison of High-Resolution Anorectal Manometry Parameters in Constipation vs Fecal Incontinence with Significant Rectal Descent by Dynamic Pelvic Magnetic Resonance Imaging

Abstract

Introduction: Clinically undetected internal rectal prolapse or significant rectal descent can be demonstrated via MRI defecography (D-MRI). It is unknown if rectal prolapse is diagnosed more frequently using D-MRI in patients with fecal incontinence (FI) compared to patients with constipation (C). The purpose of our study is to retrospectively compare the diagnostic rate of rectal prolapse in patients with constipation with that for the patients with fecal incontinence, and compare the HR-ARM findings between the two patient populations. Methods: This is a retrospective study of rectal prolapse found in patients with fecal incontinence and constipation who underwent HR-ARM and DP-MRI. Statistical analysis was performed using one-tailed Student's t test with unequal variances. Results: The rate of rectal prolapse or significant rectal descent (>3 cm) found in FI patients was 86% 12/14, versus 31% 12/39 in C patients and 50% 2/4 in patients with both FI/C. FI patients with significant rectal descent had decreased mean (57.8 vs 84, p < 0.01) and maximum (61.7 vs 92, p < 0.01) resting sphincter pressure, decreased maximum squeeze sphincter pressure (98.75 vs 219.8, p < 0.01), decreased length of functional anal canal (hpz) (2.7 vs. 3.4, p=0.01), decreased residual anal pressure (46 vs. 75.6, p < 0.01) and decreased intrarectal pressure at rest (39.4 vs 73.3, p=0.01) compared to patients with C and similar MRI findings. Conclusion: A higher proportion of patients with fecal incontinence as a presenting symptom are found to have rectal prolapse on DP-MRI than patients with constipation. A pattern of decreased resting sphincter pressure, squeeze sphincter pressure, length of functional anal canal, residual anal pressure and intrarectal pressure may be more characteristic for patients with FI and DP-MRI findings of rectal descent.Table 1: HR-ARM Comparison of Patients with Constipation versus Fecal Incontinence with Significant DP-MRI Rectal Descent