Preventive effect of biodegradable stents on biliary stricture and fibrosis after biliary anastomosis in a porcine model

Abstract

Purpose: The current drain tubes for preventing surgically biliary anastomotic stricture are not naturally and easily removed. If a drain tube using biodegradable material is easily available and the degradation time of the tube is well controlled, surgical anastomotic stricture and fibrosis could be prevented. The aim of this animal study was to evaluate the preventive effect of novel biodegradable stents (BS) on biliary stricture and fibrosis after duct-to-duct (DD) biliary anastomosis.

Methods: Ten mini-pigs were allocated to the control group (n = 5) and or the stent group (n = 5). The common bile duct was exposed through surgical laparotomy and then resected transversely. In the stent group, a 4-mm or 6-mm polydioxanone/magnesium sheath-core BS was inserted according to the width of the bile duct, followed by DD biliary anastomosis. In the control group, DD biliary anastomosis was performed without BS insertion.

Results: In the stent group, stents were observed without deformity for up to 4 weeks in all animals. Eight weeks later, histopathologic examination revealed that the common bile duct of the anastomosis site was relatively narrower in circumference in the control group compared to the stent group. The degree of fibrosis in the control group was more marked than in the stent group (3.84 mm vs. 0.68 mm, respectively; P < 0.05).

Conclusion: Our study showed that novel BS maintained their original shape and radial force for an adequate time and then disappeared without adverse events. The BS could prevent postoperative complications and strictures after DD biliary anastomosis.

Keywords: Anastomosis; Bile ducts; Biliary stents; Biodegradable; Stents.

Fig. 1. Shape of the biodegradable filaments and stents. (A, B) Scanning electron microscopic images of polydioxanone/magnesium (PDO/Mg) sheath-core monofilaments (A, surface [×50]; B, cross-section [×180]). (C) Prototype biodegradable stents were made using the cross-and-hook knitting handmade method.

Fig. 2. Trimming of the common bile duct (CBD) in the swine. (A) Exposure and isolation of the CBD. (B) Transverse cutting of the CBD. (C) Measuring the inner diameter of the transected CBD using calipers. (D) Measuring the outer diameter of the transected CBD using calipers.

Fig. 3. Process of duct-to-duct anastomosis in the swine. (A, B) Control group. Duct-to-duct anastomosis with posterior wall continuous sutures and anterior wall interrupted suture using 6-0 polypropylene monofilaments (Prolene; Ethicone, Inc., Somerville, NJ, USA) without biodegradable stent (BS) insertion. (C, D) Stent group. After posterior wall continuous suture, a 4-mm or 6-mm polydioxanone/magnesium sheath-core BS was inserted into the transected CBD. Then, the anterior wall was closed by interrupted sutures.

Fig. 4. Process of cholecystectomy in the swine. (A) Detachment of the gallbladder from the liver bed. (B) Removal of the gallbladder dividing the cystic duct. (C) Gross appearance of cholecystectomy specimen.

Fig. 5. Autopsy findings. (A) Distended intestine due to major bleeding. (B) Dark red mucosal changes in the large intestine due to ischemic changes.

Fig. 6. Fluoroscopic tracking images of the inserted biodegradable stents. The biodegradable stents were observed without deformity until 4 weeks in all swine. However, all biodegradable stents are deformed or disappeared at 6 weeks. The length of the red ladder marks represents the length of the gold marks attached to both ends of the stents without deformity. The red arrow represents the gold marks that partially existed due to the degradation of the stents at 6 weeks.

Fig. 7. Histopathologic images. (A) Gross images of the common bile ducts. The circumferences of the duct-to-duct anastomosis area (red arrows) in the stent group (specimens 2, 4, 6, 8, and 10) are wider than those in the control group (specimens 1, 3, and 7). (B) Microscopic images of the duct-to-duct anastomosis area. Masson’s trichrome staining of paraffin-embedded tissue revealed much thicker fibrosis (blue color in collagen accumulation) in the control group than in the stent group (×40).