Clinical correlates of gallstone composition: distinguishing pigment from cholesterol stones

The prevalence of cholelithiasis has been established in population-based surveys employing ultrasonography, and major risk factors have been identified. However, the clinical and epidemiological features that distinguish patients with pigment gallstones from those with cholesterol stones have received little attention.

We prospectively surveyed 551 patients undergoing cholecystectomy for gallstones at two teaching hospitals. Clinical and epidemiological data were collected during patient interviews and by chart review. Gallstones were collected at surgery; physical measurements were recorded, and stone composition was determined by visual inspection and infrared spectroscopy.

Patients with pigment stones were older than patients with cholesterol stones (p < 0.00001). Almost all patients under age 40 yr old had cholesterol stones, but most patients over 70 had pigment stones. Cirrhosis was strongly associated with pigment gallstones (p < 0.00001), although alcohol consumption was unrelated. Univariate analyses suggested associations of stone composition with male sex, diabetes mellitus, educational attainment, and use of thiazides or oral contraceptives, but these were not significant in a logistic regression that adjusted for age, cirrhosis, and other variables. Patients with pigment cholelithiasis had stones that were generally smaller in diameter and fewer in number than those with cholesterol stones.

Compared to patients with cholesterol gallstones, those with pigment stones are older and more likely to have a diagnosis of cirrhosis. In addition, their stones are smaller in size and fewer in number than those from patients with cholesterol cholelithiasis.