Benign strictures can also form within the biliary ductal system in CP, and if left untreated can lead to jaundice, cholangitis and biliary cirrhosis[41
]. Traditionally benign biliary strictures in CP are treated by surgery, but as with all surgeries the procedure is invasive and can involve significant morbidity especially if patients have other accompanying co-morbidities such as CP and/or liver disease. Morbidity and mortality of surgical treatment of post-operative biliary strictures is low, with mortality rates ranging from 0%-2.2%, whereas post-operative morbidity rates approaching almost 43% in some studies[74
]. The multiple stent placement technique was initially popularized by Costamagna et al[40
] for the treatment of postoperative strictures. In their study, stricture resolution was observed in 95% of patients at stent removal, and at follow up (average time of 38 mo after stent removal) 84% of patients were pain free and only 10.5% (2 patients) had recurrence of stricture.
They reported good long term results in treatment of post-operative biliary strictures by insertion of plastic stents after greater than a ten year follow up. While, success is dependant on the number of sessions and the number of stents placed, it appears that this maybe a reasonable first-line option[42
]. Several groups have studied biliary strictures and endoscopic approach to treatment, and in all cases average stricture resolution was reported between 10%-33% (Table )[57
Summary of studies that evaluated efficacy of endoscopic biliary polyethylene stents for treatment of common bile duct strictures
Uncovered metal stents have also been evaluated. Since biliary strictures related to CP can be difficult to treat with plastic stents, there have been several studies that examined the use of uncovered self-expanding metal stents (USEMS) in patients with primarily CP[84
]. Deviere et al[85
] deployed USEMS in patients (n
= 20) with CP, and initially demonstrated relief of cholestasis for up to 33 mo for 18 patients. Repeat ERCP 3 mo later demonstrated that the stent was embedded within the bile duct wall. All subsequent studies confirmed that uncovered metal stents proved to be problematic due to epithelial hyperplasia, occlusion, and the inability to easily remove the stent without overwhelming evidence of improved patency or stricture resolution[88
]. This lack of removability also predisposes the patient to chronic inflammation and a potential for cholangiocarcinoma.
Covered metal stent, partially or fully covered have been used, with stricture resolution for partially covered metal stent[89
] noted to be about 77% in CP, whereas fully covered metal stents provided a success rate of 83%[90
]. Given the limitations noted with uncovered stents, and in an effort to improve patency, partially covered self-expanding metal stents (PCMS) were assessed in this biliary stricture related to CP. They were noted to be easier to remove, offering the option of temporary placement[91
]. Cantù et al[94
] placed PCMS in patients with CP and associated common duct stricture who failed prior plastic stent therapy. All the patients responded initially but with a median follow up of 22 mo (range 12-33 mo), 7 patients developed stent dysfunction, requiring re-intervention. Stent patency, however, decreased over time, from 100% at 12 mo to 37.5% at 36 mo and none of the PCMS were removed during the study period, demonstrating that PCMS left in place over time decrease in patency, requiring additional endoscopic interventions[94
]. Another similar study deployed PCMS in 6 patients with limited patency (2/6) at 35 mo (range 33-37 mo) follow up. In addition, this study compared uncovered (n
= 18) to PCMS and found longer patency with uncovered stents (mean 46 mo vs
20 mo, P
= 0.002), although overall follow up was much longer for uncovered stents (mean 61 mo), which could account for the significant difference[86
Kahaleh et al[95
] performed the largest series of patients (n
= 79) with partially covered metal stents coated with Permalume (Wallstent, Boston Scientific, Natick, MA). Sixty five patients had stent left in place for a median of 4 mo (range 1-28 mo) and removed once successful treatment was confirmed. Follow up after stent removal was a median of 12 mo (range 3-26 mo). Three patients developed a stricture at uncovered proximal portion, 3 failed primary therapy and 2 developed duodenal edema preventing SEMS insertion, resulting in 90% success (59/65). Successful resolution of the stricture was noted to be lowest with strictures related to CP (17/22, 77%)[95
]. As a follow up to this study, Sauer et al[96
] further analyzed long term response of those patients. Notably, migration occurred with 15 stents, as well as intimal hyperplasia and stent embedment into the mucosa in 7 patients each respectively[96
Fully-covered self-expandable metal stents
With limitations related to partially covered metal stents namely epithelial hyperplasia at the uncovered portions and migration, fully covered metal stents (FCSEMS) were then tried in this indication (Figure ). Cahen et al[97
] published a series of 6 patients with strictures resulting from CP receiving FCSEMS (Hanaro; M.I.Tech Co., Ltd., Seoul, South Korea), with 66% resolution, however 2 stents were unable to be removed requiring plastic stents placement through the other metal stent. More recently, Mahajan et al[90
] analyzed a FCSEMS with anchoring fins (Viabil, Conmed, Utica, NY) to treat benign biliary strictures. A total of 44 patients (28 men, median age 53.5 years) were included. Etiologies included 19 CP. Complications were observed in 6/44 (14%) patients after placement, and 4/44 (9%) patients after removal, mainly pain and post ERCP pancreatitis. Lower rate of resolution was seen with CP (58%) and moderate difficulty in deploying and removing the stent due to its anchoring fins proved to be limitations in its widespread use. The anchoring fins also caused ulceration and bleeding with stent extraction[90
Fully-covered self-expandable metal stents. A: Distal biliary stricture in the setting of chronic pancreatitis; B: Placement of a fully covered metal stent (10 mm x 60 mm) draining the bile duct.
A follow up study came from the same group with 55 patients and subsequent mean stent time of 126 ± 74 d and follow up of 524.2 ± 297.7 d. The success rate was 67% for those with CP and 71% for other etiologies[96
The data that we are seeing in literature on FCSEMS are promising, but larger randomized control trials are needed to evaluate this treatment modality. It is conclusive however, that endotherapy in treatment of biliary strictures is a good option for high risk surgical patients and for those who prefer a less invasive approach.