S3565 When the Flow Stops: Functional Biliary Obstruction Secondary to Chronic Opioid Use

Introduction: Sphincter of Oddi dysfunction (SOD) is a functional biliary disorder that can mimic obstructive pathology despite the absence of anatomical abnormalities. While often associated with post-cholecystectomy states, SOD may also be induced by chronic opioid use. Diagnosing opioid-related SOD remains difficult due to nonspecific symptoms and limitations of routine imaging. Case Description/Methods: A 55-year-old woman with epilepsy, type 2 diabetes, and recurrent pancreatitis presented with a year-long history of colicky upper abdominal pain, worsened by fatty foods and accompanied by nausea and vomiting. Vital signs and most lab values were unremarkable except for a mildly elevated alkaline phosphatase. Imaging (ultrasound, computed tomography, magnetic resonance cholangiopancreatography [MRCP], and endoscopic ultrasound) showed dilated bile and pancreatic ducts without definitive obstruction. A urine drug screen was positive for opioids, and the patient admitted to long-term use. Based on her symptoms, intermittent liver enzyme elevation, and the absence of structural lesions, she was diagnosed with Milwaukee Type II opioid-induced SOD. Treatment included low-dose amitriptyline and lifestyle modifications. Discussion: Opioids can elevate sphincter of Oddi tone via μ-opioid receptor activation, leading to functional outflow obstruction. This mechanism, though documented physiologically, is often underrecognized in clinical practice. In patients with chronic opioid use and biliary-type pain without visible obstruction, SOD should be considered. In this case, conservative management with a tricyclic antidepressant, not contraindicated in seizure disorders, alongside dietary and behavioral recommendations, provided a safer alternative to invasive intervention. Early recognition of opioid-induced SOD can help avoid unnecessary procedures and guide effective symptom control.