Calcium absorption in bone disease associated with chronic cholestasis during childhood. Fractional absorption of calcium was determined in 9 children aged 4.9 to 16.9 yr with chronic cholestatic liver disease to determine the role of calcium malabsorption in the development of metabolic bone disease. Radiological evidence of rickets was absent in all patients, but bone density, measured by single beam photon absorptiometry of the distal radius, was reduced in eight of nine subjects. Serum calcium and phosphorus concentrations were normal in all except one subject. Serum 25-hydroxyvitamin D concentration was decreased compared with controls in only one of nine patients, but serum 1,25-dihydroxyvitamin D concentrations were diminished in seven of nine subjects. In all subjects, dietary calcium and phosphorus intakes were greater than 80% of the RDA. Fractional absorption of calcium, determined by oral and intravenous administration of stable calcium isotopes, was similar in cholestatic compared with control subjects (37.1% +/- 12.5% vs. 34.0% +/- 16.4%). In the cholestatic subjects, calcium absorption correlated with serum 1,25-dihydroxyvitamin D (r = 0.871, p less than 0.002) but not 25-hydroxyvitamin D concentrations. Calcium balance, assessed by the duplicate diet method, was positive in four of five subjects. Anthropometric measurements were performed to examine the relationship between nutritional status and bone mineral content. Heights of all subjects were less than or equal to the 10th percentile and fat stores and somatic protein stores were less than the 25th percentile in six of nine subjects. We conclude that factors other than calcium malabsorption and decreased serum 25-hydroxyvitamin D concentration contribute to diminished bone mass in children with cholestatic liver disease. 