Awaiting the Ideal Metal Biliary Stent

Dear Sir,

Biliary metal stents have been available for a decade but are infrequently used due to a lack of strong indications and their high cost. Papers are few, and the experience of all biliopancreatic teams is less than with the plastic stent; thus a paper like that of Ferlitsch et al. is welcome [1]. The paper describes a prospective uncontrolled multicenter experience regarding the insertion of 134 Diamond biliary stents (Boston Scientific, Natick Massachusetts, USA), the largest series reported so far. When the metal biliary stent became available a decade ago, we greeted it with great enthusiasm, but since then it has not achieved the status of ideal stent and clinicians continue to seek the perfect biliary stent [2]. I have read the paper by Ferlitsch et al. with great interest, and I wish to discuss some points.

The main indication today for the use of a metal stent and not a plastic one is an anticipated survival beyond 3 months - but this is a very difficult criterion, so much so that in these referral centers 30 % of treated patients were lost before this time [2]. The metal stent was the stent of choice in 60 % of patients, since only 40 % of them had previously had a plastic stent. This is an interesting datum for the endoscopic community as it can show the advantage of a wider early choice of metal biliary stent when indicated by current criteria. Six patients with papillary or jejunal cancer were treated, although these tumors are not such a good indication for an uncovered metal stent with a large mesh, and it would be interesting to know the outcome in this subgroup of patients. Of the inserted stents, 23 % crossed the hilum, but obstruction of the proximal third of the bile duct is reported only in 12 % of the patients, thus the decision to cross the hilum without hilar stenosis and the outcome in this subgroup of patients needs more elaboration [2]. Ferlitsch et al. report that 33 % of the biliary stents were placed with the distal end above the papilla; however it would also be helpful to know the outcome in this patient subgroup and the criteria for this choice. The parameter for definition of successful drainage (resolution of jaundice or at least 50 % reduction within 5 days of insertion) appears very high. A similar drop of bilirubin value in 98 % of treated patients may be a result which is unlikely to be found in other experiences. The rate of decrease of the bilirubin value depends not only on stent patency but also on other parameters such as liver function. Information about the mean bilirubin value before stent insertion is lacking in this paper. The median time from diagnosis of neoplastic biliary stenosis to metal stent insertion was 3 months with a range up to 130 months, a very high survival rate for a neoplastic biliary patient. Thus, more information would be useful, concerning for instance previous endoscopic treatment, the outcome with the metal stent, and the etiology of the stenosis. Two patients died from sepsis some days after metal biliary stent insertion: does this occur in the case of incomplete drainage?

Three patients had insufficient metal stent expansion, requiring balloon dilation which was successful in two of them. Might Ferlitsch et al. supply more information about the charactestics of the stenoses involved? It would be interesting to know whether these stenoses had common characteristics which were different from the others, where the Diamond metal stent expanded well; for example, whether they were particularly hard and whether they were among those needing balloon dilation before stent insertion. I would also like to know the outcome in the 9 % of patients who required balloon dilation before metal stent insertion and in the patients who required balloon dilation of the metal stent. Is it possible that the stenoses in these patients could be better treated by other types of metal stent, with a higher radial force? Also because stenoses due to metastatic lymph nodes are usually the hardest, it would be useful to know whether these show differences in metal stent insertion and outcome, and what is the incidence of duodenal stenosis in the follow-up, as these data may suggest an advantage in a wider early use of the metal biliary stent. The median duration of patency was based on eight surviving patients, but the paper lacks more information about this subgroup of patients. I agree with Ferlitsch et al. that the improvement in the radiological visibility of the new version of the Diamond biliary stent is an obvious advantage in the correct insertion of the stent, especially for better control of the proximal end (the distal end is better controlled endoscopically). I agree that the shortening by approximately 30 % which is presented during the release is not a great technical problem. In my experience of more than 40 Diamond biliary stent insertions, I have had only one incorrect positioning, caused by inability to control the distal end in the first patient treated.

I agree that there is currently no perfect metal biliary stent, but might the Diamond biliary stent be the ideal stent in some types of stenosis (e. g. neither very hard or very friable, not requiring balloon dilation, etc.)? Progress is being made but we await the availability of a pharmacologically active stent, which costs less, and is removable, etc. In the meantime, there is a dilemma: do we really need an ideal metal stent for all conditions or would several stents be better, each one optimal for particular conditions? Do we not require criteria for the correct use of stents, which need however a frequent-user to be user-friendly [3]?

References

• 1 Ferlitsch A, Oesterreicher C, Dumonceau J M. et al . Diamond stents for palliation of malignant bile duct obstruction: a prospective multicenter evaluation.  Endoscopy. 2001;  33 645-650
• 2 Gostout C J. Is there an ideal biliary metal stent? [editorial].  Endoscopy. 2001;  33 703-704
• 3 Mosca S. Is ERCP a procedure for all, the majority, or just a few endoscopists? A dilemma [letter].  Gastrointest Endosc. 2001;  54 140-142