Dissolution of calcified gallstones. Part II. Evaluation of edetic acid preparations for dissolution of residue after in vitro methyl tert-butyl ether treatment.

Rationale And Objectives: The authors assessed the potential of edetic acid (EDTA) preparations to dissolve the residue of calcified gallstones partially treated with methyl tert-butyl ether (MTBE).

Methods: Nineteen triplets (57 gallstones) were submitted to dissolution in EDTA, urea-EDTA, and an MTBE control for 48 hours after initial partial dissolution in MTBE for 24 hours. Results were compared with findings at specimen computed tomography and crystallographic analysis. All data were corrected for differences in stone size.

Results: In all three treatment groups (EDTA, urea-EDTA, MTBE), almost identical dissolution outcomes were observed within each triplet. Most triplets that dissolved displayed a laminated or a core-calcification pattern and consisted primarily of cholesterol. Specimens that dissolved poorly in all three groups displayed dense calcifications or thick calcified rims and were classified as pigment stones.

Conclusion: Because no statistically significant differences in dissolution were found among the EDTA, urea-EDTA, and MTBE treatments, we conclude that EDTA preparations are not superior to the continued use of MTBE for dissolution of residue after initial MTBE treatment.