BACKGROUND: The Endocoil (Instent Inc., Minneapolis, MN) is a new spiral nitanol stem designed for treatment of esophageal and biliary strictures. AIMS: To determine the feasibility of endoscopic placement of the Endocoil in the pig common bile duct (CBD) as a potential training and experimental model, and to demonstrate radiographic and histologic changes and endoscopic removability one and three months after placement. METHODS: Adequate sedation was achieved utilizing a combination of ketamine and xylazine administered initially intramuscularly and subsequently intravenously. The third portion of the duodenum could be reliably reached through the large "J"-shaped stomach of 60-90 lb. pigs from a long scope position utilizing an Olympus (TJF 20) side-viewing endoscope. The papilla, located 1 cm distal to the pylorus, could then be addressed by withdrawing to a short scope position. Cannulation was achieved with a standard cannula oriented toward the "2 o'clock" position, occasionally facilitated by a 0.035 inch hydrophilic guidewire. Stents were placed over the "Zebra" (Microvasive Inc., Boston, MA) guidewire. RESULTS: Nine stent placements were attempted in 7 pigs with excellent technical results in 6 attempts (66%). Bile duct (BD) perforation occurred twice (22%) and suboptimal deployment twice (22%) [perforation and suboptimal deployment occurred during one attempt on one occasion]. Two pigs died of cholangitis within one week of stent placement. At necropsy they had dilated proximal ducts full of pus, with apparent obstruction at the proximal end of the stent. Four pigs with successfully placed stents underwent follow-up evaluation four weeks later. Three stents placed across the papilla were no longer present. One of these pigs had dilated BD's, but no apparent point of obstruction. The fourth pig had a stent placed above the papilla. Four weeks later cholangiography showed obstruction at the proximal end of the stent. Grossly there was no biofilm or epithelialization of the stent. Scanning electron microscopy of the bile duct wall in the region of the stent showed patchy denudation of the surface epithelium. Histologic sections of the bile duct wall in the region of the stent also showed patchy surface denudation. The proximal obstruction was due to a diaphragm-like subepithelial proliferation of connective tissue. CONCLUSIONS: The pig represents a feasible training and experimental model for endoscopic placement of the Endocoil in the CBD. Stents placed across the biliary sphincter in otherwise normal bile ducts may spontaneously pass. Bile duct obstruction can potentially occur in this model by twisting or pinching of biliary tissue. Significant biofilm or epithelialization did not occur on a stent within four weeks following placement above the papilla. Supported by Instent, Inc., Minneapolis, MN.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging