Composition and morphologic and clinical features of common duct stones.

No systematic study of the composition of common duct stones has been carried out to date. In this study, we assessed the chemical composition and morphologic characteristics of common duct stones from 115 patients, and compared them with gallbladder stones in 67 patients who had both. Visually and chemically, common duct stones could be divided into two groups: cholesterol stones and pigment stones. Cholesterol common duct stones contained 83 +/- 1 percent cholesterol, 2.3 +/- 0.4 percent bilirubin, and 5.5 +/- 1 percent insoluble pigment residue. Pigment common duct stones contained 7 +/- 1 percent cholesterol, 24 +/- 2 percent bilirubin, and 38 +/- 3 percent pigment residue. There were two subgroups of pigment stones: one with large amounts of bilirubin and one with large amounts of pigment residue. A high proportion (46 percent) of common duct stones were composed of pigment. Patients with pigment common duct stones were more likely to have cholangitis and pancreatitis than were patients with cholesterol stones. It was not possible to distinguish primary from secondary stones on morphologic grounds. In 65 of 67 patients (97 percent), gallbladder stones and common duct stones were of the same chemical type. Morphologically, cholesterol common duct stones were very similar (3.6+ on a scale of 0 to 4+) to their counterparts. Pigment common duct stones and gallbladder stones were less similar (2.4+). Chemically, cholesterol common duct stones were identical to their gallbladder counterparts. Pigment common duct stones regularly contained a greater fraction of bilirubin and less pigment residue than associated gallbladder stones (p less than 0.05). Earthy common duct stones were associated with earthy gallbladder stones, and were chemically indistinguishable from other pigment stones. These data suggest that all cholesterol common duct stones, and when the gallbladder is present, most pigment common duct stones, are secondary. The latter stones, however, probably grow after entering the duct, adding pigment with a high proportion of bilirubin relative to pigment residue.