121 Opioid Use Are Independently Associated with Rectal Hyposensitivity and Dyssynergic Defecation in Chronic Constipation

INTRODUCTION: The role of defecation dysfunction (DD) and rectal sensitivity in opioid related chronic constipation (CC) is unknown. The purpose of this study is to evaluate the relationship between opioid use and rectal sensation, defecatory function, and balloon expulsion on physiology testing. METHODS: This was a retrospective cohort study of consecutive adult patients who underwent high-resolution anorectal manometry (HRAM) at a tertiary care center for CC. Baseline patient clinical characteristics and HRAM findings were reviewed. Rectal hyposensitivity was defined by increased rectal sensation volume for first sensation, urge, and maximal tolerance. DD was defined by impaired anal sphincter relaxation (<20% decrease from resting pressure) during strain maneuver with or without weak push, defined as inadequate rectal contraction pressure (<40 mmHg increase from baseline). Successful balloon expulsion was defined by evacuation of 50 mL balloon within 2 minutes. Statistical analyses were performed using Fisher exact or student t-test for univariate analyses and logistical or general linear regression for multivariate analyses. RESULTS: 317 patients (mean age 50.3 years; 86.8% female) were included. Patients with recent opioid use (<3 months of HRAM) had significantly increased volume for first rectal sensation (70.4 mL vs 61.5, P = 0.043), urge sensation (120.4 vs 104.5, P = 0.04), and maximal tolerance (170.2 mL vs 149.6, P = 0.0083) when compared to those without recent opioid use. No significant difference in rectal sensation was found in patients with a distant history of opioid use (>3 months) (Figure 1). Patients with recent opioid use also had increased risk of DD (63.4% vs 44.9%, P = 0.029), but no difference in failed balloon expulsion (75.9% vs 74.8%, P = 0.90). On multivariate analyses after controlling for potential confounders including history of irritable bowel syndrome (IBS), age, sex and history of abdominal or pelvic surgeries, recent opioid use (<3 months), but not distant use (>3 months), remained independently associated with increased volume for urge sensation (β-coefficient 14.3, P = 0.03) and maximal tolerance (β-coefficient 22.8, P = 0.006), and higher risk for DD (OR 1.67, P = 0.04) (Table 1). CONCLUSION: Recent opioid use was an independent risk factor for rectal hyposensitivity and DD on HRAM in patients with CC, but that effect may decrease with discontinuation of use. Anorectal physiology testing may be considered in patients on opioids with CC.