SAN DIEGO – Biliary duct dilation in the setting of an intact gallbladder and normal bilirubin levels was more common among those who used opioids, based on the results of a large, retrospective, single-center cohort study.
Patients were included in the study if they had a documented measurement for the diameter of the common bile duct, with no evidence of an obstructive lesion and a normal bilirubin level. The mean common bile duct diameter was significantly higher at 8.67 mm for 867 patients who used opioids, compared with 7.24 mm for 818 similar patients who did not use opioids (P less than .001). The association was strongest among opioid users with an intact gallbladder.
“Opiate use is associated with biliary dilation in the setting of normal bilirubin,”, a gastroenterologist at Stanford (Calif.) University, reported at the annual Digestive Disease Week. “Known opiate users with normal LFTs [liver function tests] may not require expensive and potentially risky endoscopic evaluation for biliary dilation.”
Dr. Barakat and senior author, professor of gastroenterology and hepatology at Stanford, decided to examine a possible association between biliary duct dilation and opioid use based on previous small clinical studies that found a possible association. Along with opioid status, Dr. Barakat and her coauthor also looked at patient age, cholecystectomy status, ethnicity, weight, and height for possible associations with bile duct diameter.
The researchers took a random 20% sample of adults seen for all causes in the ED at Stanford over a 5-year period. Using a health informatic platform based on the electronic medical record, they identified all patients who had received an abdominal CT or MRI. Patients were included in the study if they had a documented measurement for the diameter of the common bile duct, with no evidence of obstructive lesion and a normal bilirubin level.
Compared with 818 patients who did not use opioids, the 867 patients who used opioids had a significantly larger common bile duct diameter. Using 7 mm as the threshold for biliary duct enlargement, 84% of patients who used opioids had an enlarged common bile duct, compared with 27% of nonopioid users (P less than .001), said Dr. Barakat, recipient of an early investigator award for the study.
“We frequently get referrals for bile duct dilation with concern for more sinister causes of biliary duct dilation – stones, strictures, and malignancy,” said Dr. Barakat. Because of the increase in cross-sectional imaging via CT or MRI, bile duct dilation is being detected at increasingly higher rates.
Dr. Barakat said that about one-third of referrals to the therapeutic endoscopy clinic at Stanford are now for patients with biliary dilation and normal liver function tests. And similar increases are being “seen across all settings – so office, primary care clinic, inpatient, and most markedly, the emergency department. Coupled with this, the population is aging, and patients who present to each of these settings are more likely, if they are older, to undergo cross-sectional imaging.”
Other contributors to higher rates of bile duct dilation include increased rates of obesity and increased prevalence of nonalcoholic steatohepatitis (NASH). About 20% of individuals with NASH will also have abnormal LFTs, she said, and NASH can be the trigger for cross-sectional imaging.
For most of these patients with biliary duct dilation and normal LFTs, no obstructive process was found on endoscopic evaluation.
Although gastroenterology textbooks may say that bile duct diameter increases with age, Dr. Barakat and colleagues didn’t find this to be the case. Among nonopioid users in the study cohort, age did not predict of common bile duct diameter. Among the entire cohort, “Advancing age weakly predicts increased common bile duct diameter,” she said, suggesting that factors other than age along may drive increased bile duct diameter.
Limitations included the retrospective nature of the study, as well as the limitations of information from the electronic medical record. Also, interobserver variability may have come into play, as bile duct diameter measurements were made by multiple radiologists in the course of clinical care.
The study was funded by the National Institutes of Health. Dr. Barakat reported no relevant financial disclosures.