Microprocessor-assisted solvent transfer system for effective contact dissolution of gallbladder stones.

Abstract

Dissolution of cholesterol gallbladder stones by manual lavage with methyl tert-butyl ether (MTBE) via a percutaneous indwelling gallbladder catheter is reviewed. The procedure is labor intensive and requires several hours, is associated with escape of solvent into the biliary tract, and is incomplete since residue remains. To solve these problems, a microprocessor-assisted solvent transfer (MST) system was developed. The system consists of a three-lumen catheter, dual peristaltic pumps, a pressure transducer, and a microprocessor controller which regulates pump rate according to the measured intraluminal gallbladder pressure. The two pumps simultaneously infuse and aspirate from the gallbladder via two of the catheter lumens; intraluminal pressure is monitored using the third lumen. An increase in intraluminal pressure above a set limit causes infusion to cease while aspiration continues, thus lowering the pressure and preventing overflow of gallbladder contents into the biliary tract. In vitro evaluation showed that the system's response was 156 fold faster than the natural rate of gallbladder emptying. The time required for gallstone dissolution by MTBE was measured in vitro using the MST system and found to be 48 +/- 23 (M +/- SE) min at 100 mL/min flow, 15 +/- 5 min at 150 mL/min flow, 12 +/- 4 min at 200 mL/min flow, and 6 +/- 1.4 min at 250 mL/min flow. No residual debris remained with flow rates greater than 150 mL/minute. These in vitro studies suggest that the MST system is capable of rapid, complete, and fully automatic contact dissolution of cholesterol gallbladder stones using MTBE or similar lipid solvents.