Evaluation of an oral ursodeoxycholic acid load in the assessment of bile acid malabsorption in cystic fibrosis.

Serum levels of ursodeoxycholic acid (UDCA) were measured by radioimmunoassay in 20 children with cystic fibrosis (CF) and in eight controls, who had received 300 mg of this bile acid orally. Area under the curve (AUC) after UDCA load was significantly reduced (25.24 +/- 9.54) in CF patients, as compared to controls (52.98 +/- 5.87 mean values +/- SD percent dose/liter X hr X kg body weight, P less than 0.001). AUC values were compared with daily fecal bile acids (BA) and fat excretion, and with serum fasting conjugated cholic (CCA) and chenodeoxycholic (CCDCA) acid levels. Total fecal BA were increased in CF patients (7.84 +/- 5.57 mg/kg/day) as compared to control values (2.7 +/- 1.1 mean +/- SD, P less than 00.5); they were inversely correlated with AUC values (r = 0.48) but not with steatorrhea (r = 0.32). UDCA load seems to be useful in detecting BA malabsorption in CF. Fasting CCA levels did not significantly differ in CF patients (0.87 +/- 0.61 mumol/liter) and in controls (0.60 +/- 0.26 mumol/liter) and did not correlate with fecal BA excretion. Fasting CCDCA mean levels were significantly increased (mainly in CF patients with liver damage), suggesting a lowered first-pass extraction in the liver: their determination may be useful in the follow-up of liver involvement in CF.