Objective: One of the best known side effects of using opium is spasm of the sphincter of Oddi, which may increase the diameter of the extrahepatic bile ducts. Ultrasound is the first imaging modality used for evaluating the biliary system because it is commonly available and noninvasive. The principal objective of this study was to measure the common bile duct (CBD) diameter via ultrasonography in opium addicts and to evaluate the relation between the CBD diameter and the period of addiction. Materials and Methods: This research was an analytical-cross sectional study that was done on 110 opium addicts that were admitted to a drug treatment center. The diameter of the CBD in these cases was measured by ultrasonography and the results were analyzed with other factors like age, the period of addiction and the laboratory findings. Results: According to the findings, there is a significant increase in the range of the CBD diameter in comparison with normal bile ducts. Also, the mean diameter of the CBD in the different age groups showed a significant difference (p < 0.0001) and there was a significant relation between the CBD diameter and the period of addiction (p < 0.001, r = 0.74); so, with the increased length of the addiction period, the mean CBD diameter increases. Conclusion: Opium addiction is one of the factors that causes extrahepatic bile duct dilatation, so in these cases, if no obstructing lesion was found on ultrasound examination and the serum bilirobine and alkaline phosphatase levels are normal, then further evaluation is not needed.
