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Original Report |
1 All authors: Department of Diagnostic Radiology, University Clinics of Ulm, Robert-Koch-Str. 8, D-89081 Ulm, Germany.
Received December 26, 2000;
accepted after revision April 17, 2001.
Address correspondence to A. Gabelmann.
Abstract
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CONCLUSION. The clinical course of these patients is compromised by repeated stent occlusions, caused by stone or mucosal hyperplasia. The results of primary stent patency are disappointing with the primary patency rate decreasing from 75% after 12 months to 25% after 36 months. The different interventional procedures used to restore bile flow make an important contribution to the secondary stent patency and provide a satisfactory clinical result in a patient subpopulation in whom stent placement is considered the last resort.
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Placement of metallic stents in benign biliary strictures has been proposed as another alternative modality [5]. In benign obstructive processes, however, assessments of the judicious use of metallic stents and the overall clinical value of this treatment remain questionable because long-term patency remains unsatisfactory, having a primary patency rate between 38% and 46% after 36 months [6, 7]. On the other hand, stent placement can represent an alternative before long-term drainage with indwelling catheters or even before liver transplantation. Unfortunately, almost all implanted stents will occlude after a certain period of time [7]. The clinical value of stent placement is, therefore, mainly characterized by the possibility of achieving secondary patency.
We report on our experience with the effectiveness of metallic stents in benign biliary obstructions with special consideration given to the interventional techniques used to achieve secondary patency.
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Causes and locations of benign biliary strictures were as follows: recurrent stricture of hepaticojejunostomy (n = 5) (Fig. 1A,1B), injury of intrahepatic bile ducts during placement of a Port-A-Cath catheter (n = 1), injury of intrahepatic bile ducts during surgery due to gallbladder perforation (n = 1), intrahepatic stricture caused by liver resection (n = 1), multiple intrahepatic strictures associated with primary sclerosing cholangitis (n = 1), stricture of the common bile duct after recurrent intra- or extrahepatic stones associated with Billroth II reconstruction (n = 2) (Fig. 2A,2B,2C,2D), and stricture of the distal common bile duct due to chronic pancreatitis (n = 1) (Fig. 3A,3B).
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Patients were followed up clinically and by means of imaging to assess patency of the stent and position of the stent to rule out stent migration. A stent was considered patent if follow-up imaging showed the caliber of the extra- or intra-hepatic bile ducts to be normal, if the bilirubin and alkaline phosphatase levels were normal, and if the patient had no symptoms of recurrent jaundice.
We implanted the shortest stent possible, treating only the strictured segment and making the Palmaz stent (Cordis Endovascular; Haan, Germany) or the Accuflex stent (Boston Scientific Europe, Ratingen, Germany) the stent of choice. Accordingly, strictures of the common bile duct and strictures of a hepaticojejunostomy were treated by insertion of either a Palmaz stent (n = 4) or an Accuflex stent (n = 4). The Wallstent (n = 4) (Schneider, Boston Scientific Europe) was used only in patients in whom a hilar lesion or a stricture of the central portion of the right or left intrahepatic bile duct was identified.
Stent revision was performed as a multistep procedure. The first step consisted of creation of external access to the biliary tree to allow external drainage. The second step included gradual dilatation of the transhepatic tract up to 14-French for cholangioscopic evaluation. With this procedure, additional information could be obtained about the nature of restenosis and the degree of secondary sclerosing cholangitis, if present, both of which helped in planning the revision procedure. Furthermore, this protocol allowed shock wave lithotripsy in cases of obstructive stone formation, with a 3-French electrohydraulic lithotriptor probe for stone fragmentation.
In one patient with repeated occlusions of a Wallstent, caused each time by mucosal hyperplasia, we made an attempt to overcome this problem by application of intraductal radiation therapy, using the liquid high-energy ß-emitter rhenium-188 as a radiation source, applied via a balloon catheter. The targeted dose was calculated to deliver 7.5 Gy in a tissue depth of 0.5 mm. The third step included final revision of the implanted stent by either placement of an additional stent or by balloon dilatation.
The period of time in which a patient had a patent stent was described as the primary patency. A single episode of cholangitis without evidence of stent occlusion was considered an adverse event. The stent was considered occluded if the patient had recurrent jaundice associated with dilatation of the prestenotic bile ducts. Secondary patency was defined as the total time of stent function with the contributions of all stent revisions, whether they were single or multiple.
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Primary patency was obtained in six patients with a median follow-up of 31 months (range, 12-61 months). In four patients, the clinical follow-up showed the patients free of symptoms until the end of the observation period. Two patients experienced a single episode of cholangitis, which was considered an adverse event.
In six patients, the stent occluded after a median follow-up of 15.5 months (range, 6-30 months). In two patients, patency was reestablished by a single recanalization procedure resulting in a secondary patency of 45 and 46 months.
Two patients underwent multiple stent revisions during follow-up. One patient exhibited a complex stricture configuration, involving the hilar and intrahepatic bile duct segments after extensive surgical manipulation related to gall-bladder perforation. Twelve months later one of the two implanted Wallstents occluded because of mucosal hyperplasia. Occlusion was revised by additional implantation of a Wallstent. Five months later the other stent occluded for the same reason and was revised the same way. After another 6-month period, the primary revised stent occluded again, also caused by mucosal hyperplasia.
To overcome the problem of ongoing stent occlusion, we decided to make a treatment attempt with intraductal radiation therapy. Brachytherapy was applied at both stent implantation sites and resulted in a fourth period of patency with a stent remaining patent for more than 21 months.
In a second patient, initial stent placement was performed to cover a stricture of a hepaticojejunostomy after segmental liver resection in echinococcosis. Stent reocclusion occurred four times, at intervals between 11 and 24 months, caused by a multifactorial process of mucosal hyperplasia, bile sludge, and stone formation. Recanalization was performed by cholangioscopic lithotripsy, by stent redilatation, or by insertion of an additional stent.
Two of the six patients with stent occlusion died as a result of ongoing cholangitis, despite a morphologically and functionally successful stent revision.
Four of the 12 patients showed procedure-related complications associated with the first stent implantation. Two patients developed moderate postprocedure cholangitis; one patient developed hemobilia, which was successfully treated by embolization. One early stent dislodgement occurred within 24 hr after implantation. Late stent migration was not noticed. Only one bile leakage to the skin through the 14-French tract after cholangioscopy was associated with a stent revision procedure, and it resolved within 14 days after drainage.
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Surgery is still considered the best treatment with a primary success rate of up to 90% [1]. However approximately 30% of patients undergoing further surgery develop recurrent strictures [2]. Percutaneous cholangioplasty is an alternative, but the primary patency rates reported vary from 67% to 73% in anastomotic strictures and 76% to 88% in ductal strictures and decrease to 42% for strictures associated with sclerosing cholangitis [4]. In liver transplant recipients, the results of balloon cholangioplasty are inhomogeneous, varying from a complete treatment failure in all patients [8] to an overall patency of 70% at 6 years [9]. Unfortunately, however, strictures recur after cholangioplasty, and 80% of recurrences become clinically evident within 3 years [4].
The use of metallic stents for treating benign postoperative strictures has been postulated, and early results were promising, with short-term patency rates of 82.4% after 8 months [10]. But as long-term results began to be reported, the picture changed completely. The somewhat optimistic long-term patency rate of 68.7% after 36 months and of 55% after 78 months reported by Maccioni et al. [11] could not be confirmed in other series. Corresponding to a primary patency rate of 25% after 36 months in our study, other series reported a primary patency from 20% to 44% [7, 8], dropping to 19% after 5.5 years [6] or even 0% after 5 years [7]. Our results confirm that an overall good or satisfactory long-term primary patency of several years' duration was achieved in only a minority of patients.
In our experience, the realistic scenario for patients undergoing stent implantation includes episodes of cholangitis or stent occlusion. Therefore, the clinical value of this method is determined not only by the primary patency; it is the secondary patency that makes an essential contribution to the clinical outcome. That secondary patency can be achieved with excellent results has also been shown by Culp et al. [7], with a patency of 94% after 1 year and 88% after 5 years.
Stone or sludge formation may be due to the ongoing natural disease process. In cases of large stones, contact electrohydraulic lithotripsy can be effectively used to fragment stones, to facilitate spontaneous passage, or to prepare residual stone fragments for extraction [12]. In combination with endoscopic guidance, as performed in this study, the procedure proved highly effective. The procedure requires a subsequent careful cleaning of the bile ducts with removal of all stones by flushing techniques to avoid repeated stent obstruction.
Adequate treatment of mucosal hyperplasia can represent a more difficult problem. Successful treatment by repeated balloon dilatation and stent placement has been reported, but often permanent tube drainage with internal external biliary drains is required [6, 7]. A theoretic approach to overcome the problem of exuberant hyperplasia is intraductal radiation therapy. Brachytherapy was performed with high-energy ß-emitters 188Re because of its low penetration depth. Filling a conventional balloon catheter with liquid 188Re results in a self-centering irradiation source independent from bending of the bile duct. With this treatment, we could interrupt the process of continuous mucosal hyperplasia formation, providing the longest patency period the patient ever had. On the other hand, a stent-related effect could not be excluded, and it appears even likely that implantation of Wallstents can be associated with a hyperplastic mucosal response [7].
Over time, it became apparent that one of the main factors influencing the outcome of stent placement in benign biliary obstruction was the choice of the stent type. Actually most experience has been gained with the use of the Gianturco stent (Cook Europe, Bjaeverskov, Denmark) [7, 10, 13], and this stent type has shown a clear superiority over all other stent types. Although the number of Palmaz and Accuflex stents implanted during this study is limited, both stent types yielded a satisfactory long-term primary patency for up to 61 months. The different outcome between the stent types may be partially explained by the amount of metal exposed to the mucosa, implicating the metallic stent surface as a major trigger for mucosal stimulation [6, 7].
Our study has several shortcomings. First, it was a retrospective study; therefore, not all patients underwent treatment according to an identical protocol. The patient population was not homogeneous because of different clinical situations at the time of stent implantation, the nature of the stricture, stent position, and type and length of stent used. Finally, the patient population in our study was too small to allow definite conclusions.
However, a note of caution is mandatory with regard to using metallic stents for benign strictures and stent implantation. Our patient series followed the guideline that the procedure was the last resort for recanalizing the biliary tree. Nevertheless, this treatment option offers the opportunity to reestablish bile flow and to improve a patient's quality of life because repeated surgical repair or a long-term indwelling catheter is generally distressing and undesirable, without offering any guarantee of permanent patency. The clinical value of stent implantation in benign biliary strictures is not only determined by the primary patency; it is the secondary patency that makes an essential contribution to the patient's quality of life.
The decision to use a metallic stent in a benign biliary stricture must be made on an individualized basis. If it is the best option, under the circumstances, to place a metallic stent, then certainly it can be used.
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