Microprocessor-assisted solvent-transfer system for gallstone dissolution. In vitro and in vivo validation.

To improve the efficacy, safety, and convenience of contact dissolution of gallbladder stones, a microprocessor-assisted solvent transfer system was developed. The system's two pumps simultaneously infuse and aspirate solvent into and from the gallbladder at a high flow rate through a multilumen catheter. The microprocessor controls the pumps using a closed feedback loop control algorithm to regulate intragallbladder pressure to prevent solvent escape into the duodenum. Turbulent solvent flow at the catheter end in the gallbladder is designed to induce rapid stone dissolution and to suspend insoluble residue, thus promoting its aspiration. The system's response and gallbladder emptying capacity was 160-fold faster than the natural gallbladder emptying rate. The rate at which gallstones were dissolved by methyl tert-butyl ether using the system was compared with that achieved with a syringe pump. For 6 of 11 pairs of stones that totally dissolved, the mean dissolution time with the system was 10 +/- 6 minutes compared with 112 +/- 81 minutes for the syringe pump. In the 5 of 11 stone pairs which dissolved incompletely, insoluble residue was completely eliminated by the system in 21 +/- 9 minutes but not by the syringe pump even at 360 minutes. When the system was used in gallstone patients, solvent recovery was 99% +/- 1%, and the concentration of a nonabsorbable marker did not change, confirming the lack of appreciable absorption of methyl tert-butyl ether. These studies suggest that the microprocessor-assisted solvent transfer system is a device capable of safe, complete, and fully automatic contact dissolution of cholesterol gallbladder stones using methyl tert-butyl ether or similar solvents.