Joshua Guttman, MD, FRCPC
Lahham S, Becker BA, Gari A et al. Utility of common bile duct measurement in emergency department point of care ultrasound: A prospective study. Am J Emerg Med. 2017 Nov 18. pii: S0735-6757(17)30892-6. doi: 10.1016/j.ajem.2017.10.064.
Measurement of the common bile duct (CBD) internal diameter is considered to be part of the standard evaluation for biliary pathology on point of care ultrasound (POCUS). However, finding the CBD can be difficult and time consuming on some patients. Previous retrospective studies have challenged the dogma of requiring CBD evaluation on all biliary point of care ultrasounds, showing that emergent biliary pathology is rarely associated with isolated CBD dilation and normal lab values. These studies suggest that, in the absence of other findings on biliary POCUS and normal lab values, CBD measurement can be omitted. However, this has never been evaluated prospectively.
Lahham, et al, performed a prospective observational study on a convenience sample of patients who were getting a biliary POCUS and labs for assessment of biliary pathology. Sonographers included residents, fellows and attendings. Though no specific number of scans was required in order to enroll, all had received at least a basic ultrasound training session. They recorded final diagnosis from the ED if discharged or from hospital discharge, if admitted. Patients were contacted two weeks after discharge to assess for any change in final diagnosis. The primary outcome was the diagnosis of complicated biliary pathology (requiring acute intervention) in the absence of lab abnormalities and the absence of POCUS findings other than dilated CBD. After exclusions, 158 patients were enrolled. Approximately half of the patients had biliary pathology. Of those patients, only two were found to have an isolated dilated CBD in the absence of lab abnormalities and other POCUS findings (wall thickening, pericholecystic fluid, sonographic murphy’s sign). One case had a gallstone found on POCUS and had a radiology ultrasound indicated uncomplicated cholelithiasis. The other case was pancreatitis diagnosed based on a lipase level. There were two additional cases of complicated biliary pathology, found in the absence of lab abnormalities and POCUS findings. These were two cases of choledocholithiasis, and in both these cases, the CBD was normal. The authors conclude that in the absence of POCUS findings and laboratory values concerning for complicated biliary pathology, less than 2% of patients have complicated biliary pathology, and therefore CBD measurement can be omitted from the standard biliary POCUS in these cases.
While this study had limitations, namely having a convenience sample of patients and including all levels of sonographers, it prospectively assessed a more “real world” context, where various levels of POCUS expertise are scanning. It is consistent with previous research in this area. While the CBD can be found and measured most of the time, it is occasionally difficult and cannot be found. Based on this study and previous research, it would be reasonable not to order a follow up study (CT or radiology ultrasound) in the ED in the absence of other POCUS findings and normal lab values when the CBD cannot be found.