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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.
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.
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?
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.”
Majeed and colleagues concede that a number of previous studies have shown “a trend towards a minor degree of duct dilatation.” Do these many studies add up to a convincing dataset in favour of postcholecystectomy dilatation? Unfortunately, detailed perusal of previous studies suggests that their quality was often very poor and certainly the methodology was so variable that it is impossible to conduct anything that could be termed a true meta-analysis. Hughes and colleagues6 showed no change, whereas Hunt and Scott showed a 12.5% increase in common hepatic duct diameter in 21 patients examined five years after cholecystectomy.3 However, as in all other studies, a mean increase covered a wide range of changes, including several which had decreased in size. Grahamet al’s7 and Muelleret al’s8 papers are really not of sufficient quality to analyse but did show that only a minority of bile ducts dilate significantly. Hammarstrom’s group reported an average 27% increase in common hepatic duct diameter a mean of 62.8 months postoperatively but they also noted that those with a large increase were older than those whose ducts were normal or did not increase very much.9 Gylstorff and Faber’s study10 is uninterpretable as symptomatic patients were included, some of whom may have had retained stones and although Hamilton et al’s study5showed 66% greater bile duct diameter in post- as opposed to precholecystectomy patients, these were not the same patients and thus were not controls in the same sense as those in other studies.
The facts therefore appear to be these: bile ducts tend to dilate after cholecystectomy but in over 90% this is minor. A few patients with a more significant dilatation tend to be older and the reasons for this are not known. One cannot therefore assume that in a postcholecystectomy patient a dilated duct is simply the result of the operation and “the reservoir capacity” of the gall bladder being taken over by the duct system.
The final point must be that a patient with convincing postcholecystectomy symptoms, whatever the diameter of the duct, needs high resolution cholangiography, whether ERCP, MRCP, or endoscopic ultrasound. The converse is also true that in an asymptomatic patient whose duct is found incidentally to be dilated, no further investigation is required.