Defecatory disorders are a common cause of chronic constipation in Parkinson disease

Background and Aims Up to 50% of patients with Parkinson disease have constipation (PD‐C), but the prevalence of defecatory disorders caused by rectoanal dyscoordination in PD‐C is unknown. We aimed to compare anorectal function of patients with PD‐C versus idiopathic chronic constipation (CC). Methods Anorectal pressures, rectal sensation, and rectal balloon expulsion time (BET) were measured with high‐resolution anorectal manometry (HR‐ARM) in patients with PD‐C and control patients with CC, matched for age and sex. Results We identified 97 patients with PD‐C and 173 control patients. Eighty‐six patients with PD‐C (89%) had early PD, and 39 (40%) had a defecatory disorder, manifest by a prolonged rectal balloon expulsion time (37 patients) or a lower rectoanal pressure difference during evacuation (2 patients). PD‐C patients with a prolonged BET had a greater anal resting pressure ( p = 0.02), a lower rectal pressure increment ( p = 0.005), greater anal pressure ( p = 0.047), and a lower rectoanal pressure difference during evacuation ( p < 0.001). Rectal sensory thresholds were greater in patients with abnormal BET. In the multivariate model comparing CC and PD‐C (AUROC = 0.76), PD‐C was associated with a lower anal squeeze increment (odds ratio [OR] for PD‐C, 0.93 [95% CI, 0.91–0.95]), longer squeeze duration (OR, 1.05 [95% CI, 1.03–1.08]), lower rectal pressure increment (OR per 10 mm Hg, 0.72 [95% CI, 0.66–0.79]), and negative rectoanal gradient during evacuation (OR per 10 mm Hg, 1.16 [95% CI, 1.08–1.26]). Conclusions Compared with CC, PD‐C was characterized by impaired squeeze pressure, longer squeeze duration, lower increase in rectal pressure, and a more negative rectoanal gradient during evacuation.