Current management of opioid-induced constipation mainly focuses on improving intestinal transit. However, animal studies suggest opioids may also decrease anal sphincter relaxation and decrease sensitivity to stool in the anal canal.
Walter W. Chan, MD, MPH, director of the Center for Gastrointestinal Motility at Brigham and Women’s Hospital, Nayna A. Lodhia, MD, associate physician in the Division of Gastroenterology, Hepatology and Endoscopy, and colleagues have documented anorectal dysfunction in patients with chronic constipation who used opioids.
The findings, which included altered rectal sensation and anal sphincter dysfunction, are detailed in Digestive Diseases and Sciences.
The researchers retrospectively studied 424 adults (mean age 50, 86% female) who underwent high-resolution anorectal manometry and physiology testing for evaluation of chronic constipation at the Brigham between September 2018 and November 2019. They divided the cohort into three arms:
- Recent opioid use (55 patients, 13%)—originally defined as opioid use at the time of manometry or within three months prior, but all 55 patients were chronic, current opioid users
- Distant opioid use (63 patients, 15%)—history of prior opioid use more than three months before manometry
- No history of opioid use (306 patients, 72%)
208 patients (49%) were diagnosed with dyssynergic defecation on manometry. This was defined as impaired anal sphincter relaxation (<20% decrease from resting pressure) during strain maneuver with or without inadequate rectal contraction pressure (“weak push,” <40 mmHg increase from baseline).
On multivariable analysis, the only independent predictor of dyssynergic defecation was recent (current) opioid use (adjusted OR, 2.18; P=0.026).
Rectal sensitivity was defined by intra-rectal balloon distention volumes for first rectal sensation, urge and maximal tolerance. On multivariable analyses:
- Recent opioid use was independently associated with increased balloon distention volume for first rectal sensation (β, 9.78; P=0.019), urge sensation (β, 16.7; P=0.0060) and maximal tolerance (β, 22.9; P=0.0032), suggesting rectal hyposensitivity</li>
- Distant opioid use predicted first rectal sensation (β, 8.97; P=0.027), but not urge or maximal tolerance
Recommendations for Clinicians
Patients with opioid-induced constipation that is refractory to pharmacotherapies may benefit from an early assessment with high-resolution anorectal manometry and referral for biofeedback or pelvic floor physical therapy.
Novel therapies such as sacral nerve stimulation have been effective in human studies of defecatory dysfunction and may represent additional options. They may be especially useful as palliative measures in end-of-life care when it’s not advisable to discontinue opioids.