[Biliary calculi resistant to dissolution with bile acids: their heterogeneous composition and diversity of treatment response].

We have studied thirteen biliary stones resistant to biliary acids, using technical methods of stereomicroscopy, scanning electronic microscopy and EDX analyses. We have investigated changes on surface. Three biliary stones did not change and were considered resistant. Seven biliary stones appear partially dissolved and we observed many irregularities on surface and/or concentric dips in relation with cholesterol dissolution. In six cases, biliary pigment alternates with cholesterol. In three cases we observed a calcium carbonate coat on surface. One case included organic fibers. One biliary stone showed cholesterol with spherical bodies of calcium carbonate and pigment. It was a relapsed case of combined treatment. Three stones are composed of small black portions of polymerized calcium bilirubinate, rich in copper and iron. Our results demonstrate that biliary stones previously selected for treatment are a heterogeneous group. Because of this fact we get variable and unpredictable results.