[Role of computerized tomography in the densitometric assessment of lithiasis of the gallbladder].

Radiolucent gallstones frequently contain significant calcium deposits. Their detection is important to select the patients to submit to medical gallstone dissolution. Since CT facilitates the identification of calcifications undetected at conventional radiologic procedures, 60 patients were studied with CT. All of them had US confirmation of cholelithiasis and in the whole of cases an X-ray examination of the right upper abdominal quadrant was performed (for the identification of radiopaque stones), together with oral cholecystography (to evaluate gallbladder function). CT attenuation values of the stones were measured and the patients subsequently divided into 2 groups; the threshold value was 50 HU: below it, the stones were considered hypo- or isodense (group I); above it, they were considered hyperdense (group II). Later on, 28 patients (14 from group I and 14 from group II) were selected for chemical dissolution with ursodeoxycholic acid over a 1-year period. US examinations were performed at 6 and 12 months. Seventy per cent of the patients in group I responded to treatment (50% with complete stone dissolution and 20% with partial dissolution), whereas no patient in group II had complete dissolution and only 30% had partial response.