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what does a dilated cbd mean

Goals: A systematic review of studies on patients with dilated CBD was performed to identify etiologies and clinical factors that may predict which patients require further diagnostic testing and long-term outcomes. A PubMed search for relevant articles published between 2001 and 2014 was performed.

Background: With the widespread use of abdominal imaging, an incidentally found dilated common bile duct (CBD) is a common radiographic finding. The significance of a dilated CBD as a predictor of underlying disease and long-term outcome have not been well elucidated.

Results: The search yielded a total of 882 articles, and after careful individual review for eligibility and relevancy, 9 peer-reviewed studies were included. A cause of the CBD dilation was found on average in 33% of cases and the most common causes were: CBD stone, chronic pancreatitis, and periampullary diverticulum. The overall CBD diameter was not associated with finding a causative lesion. Coexisting CBD and intrahepatic bile duct dilation, age, and jaundice were found to be indicators of pathologic lesions. Dilation of both the CBD and pancreatic duct was suggestive of pancreatic disease, especially pancreatic malignancy in the setting of obstructive jaundice. Follow-up was reported in 6 studies ranging from 6 to 85 months, and generally there was no change in the diagnosis.

Conclusions: Incidentally found biliary tract dilatation can be a manifestation of significant biliary tract disease including malignancy. Long-term outcome is not well defined and further prospective studies examining the most cost-effective approach to evaluation are needed.

The authors report the error of the method as being around 1 mm as most ultrasound machines measure in increments of whole millimetres, and therefore discount an increase in size of 15.2% at one year. It is, however, unlikely that the error should be systematically in the same direction. In addition, it is known that the bile duct diameter increases with age, estimates ranging from 0.3 mm per decade to more than 1 mm.1-3 So on age grounds alone, the ducts should have dilated half this amount over the five years of the study.

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See article on page 741

Whether the bile duct dilates after cholecystectomy is a hoary old chestnut dating back to Oddi and hotly debated in the era of intravenous cholangiography but is still of practical importance now. In this issue Majeed et al (see page 741) report a careful, but uncontrolled study from Sheffield examining this question. Fifty nine patients undergoing cholecystectomy had their common hepatic duct diameters measured ultrasonographically before and three, six, 12, and 60 months after surgery. Those with ducts of >5 mm preoperatively were excluded. A slight mean increase was found and more importantly, perhaps, about 5% of subjects at six months and one year had ducts greater than the arbitrary cut off limit of 6 mm. At five years only one of the 48 at risk seemed to maintain the increase in size. One wonders whether the radiologist’s technique and interpretation at five years were identical to those at the outset. Furthermore, by the end of the study the ultrasound machine was at least nine years old. One assumes that image quality remained sufficiently good for the purpose throughout this period. The lack of a control group leaves these questions open.

Bolton and Le Quesne stated succinctly that,4 “the demonstration of a dilated duct in a patient who has undergone cholecystectomy is of no immediate significance unless the calibre of duct at the time of operation is known.” In clinical practice, a patient with postcholecystectomy pain rarely brings her preoperative ultrasound films or duct diameter measurements with her. The usual problem is a patient with a duct of around 1 cm in whom neither preoperative duct size nor whether the duct was explored are known. Knowing the current duct size in such an individual is of very little value. Hamilton et al,5 who did an endoscopic retrograde cholangiopancreatoraphy (ERCP) study in pre- and postcholecystectomy patients, further stated that, “methods of evaluating the biliary tract which rely on the measurement of bile duct diameter. . .are. . .of limited value in the investigation of post-cholecystectomy patients.”

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This begs two further questions: firstly, what is the importance of this study to patients and, secondly, how does it compare with other studies of the same phenomenon?