Endoscopic retrograde cannulation of the gallbladder: direct dissolution of gallstones. Percutaneous transhepatic catheterization of the gallbladder for dissolution of cholesterol stones by instillation of methyl tert-butyl ether (MTBE) is an invasive therapeutic procedure. The only non-invasive alternative available to now, endoscopic retrograde cannulation of the cystic duct, was difficult because of the cystic duct's tortuosity and spiral valves. We therefore developed a catheter system which, using conventional duodenoscopes during a routine endoscopic retrograde cholangiography (ERC) procedure, permits reliable and safe catheterization of the gallbladder without the need for endoscopic sphincterotomy. In 18 of 22 patients (82%) we were able to place a cysto-nasal catheter, and in 14 patients MTBE dissolution therapy was then performed. Eight patients (57%) were completely free of stones after treatment; the other six (43%) had residual debris. In 4 of 22 patients (18%) cannulation attempts failed, in 3 patients due to cystic duct blockage by a calculus. Endoscopic retrograde cannulation of the gallbladder (ERCG) represents a promising alternative to the invasive percutaneous transhepatic catheterization procedure. 