The purpose of our study was to evaluate the flow rates and patterns of simulated bile through drainage catheters in an in vitro biliary system model.
METHOD AND MATERIALSThe in vitro model consisted of a manometer-monitored constant pressure chamber containing simulated bile connected to a biliary tree made from airline and heat shrink cable tubing. Three types of 12-French drainage catheters (Cook Medical, Bloomington, IN) were inserted through a "T"-shaped sidearm in the biliary tree section of the model: biliary (32 sideholes along the shaft and locking pigtail), pigtail (6 sideholes within the pigtail), and a prototype pigtail catheter with a single sidehole in the catheter mid-shaft. Simulated bile at 4 different viscosities (guar gum solutions in water determined by a rotational viscometer to be in the range of human bile viscosity) flowed through the system under a constant pressure of 12 cm of water. A circumferential occlusion device was used to occlude distal flow. Flow volumes through each catheter were recorded over 1-minute intervals with the "common bile duct" unobstructed or obstructed. Ten trials were performed for each catheter and flow rates compared using Student's t-test.
RESULTSWithout obstruction, there was no significant difference in the flow rates between all catheters tested. With obstruction, there was no significant difference in the flow rates between the prototype and standard biliary catheters while no flow was observed with the pigtail catheter. Fluid was seen flowing along the external shaft of all unobstructed catheters. In the obstructed prototype and biliary catheters, fluid was seen to exit from the sidehole(s) proximal to the obstruction and out of the distal sideholes.
CONCLUSIONOur data suggest that biliary drainage may be achieved with fewer sideholes proximal to the obstruction. Similar flow rates were obtained with multiple sideholes as compared to one proximal sidehole.
CLINICAL RELEVANCE/APPLICATIONBiliary catheters with multiple sideholes do not improve flow rates and may facilitate encrustation with debris that could lead to catheter obstruction and sepsis. Catheters with one or fewer sideholes may achieve the same flow rate while reducing the likelihood of catheter obstruction.