Ion pair extraction technique with azure A, for differentiating biles of normal subjects and patients with liver disease from patients with Crohn's disease with small bowel involvement.

The ion pair extraction technique with Azure A solution, chloroform/methanol (equal volumes), and dilute sulfuric acid, was used to study bile-rich duodenal aspirates of (a) healthy volunteers and patients with (b) cholestatic liver disease, (c) Crohn's disease with small bowel involvement, and (d) those with primarily colon involvement. Duplicate aliquots of extracted duodenal aspirates from these four groups were subjected to ion pair extraction, with and without prior acetylation, and the absorbance ratios at 645 nm without acetylation/with acetylation ("acetylation index") compared; values (+/- SD) obtained were 0.052 +/- 0.0098, 0.038 +/- 0.014, 0.136 +/- 0.048, and 0.077 +/- 0.056, respectively, for the four groups. The acetylation index for group c was significantly (P less than 0.001) different from that of groups a and b. All other intergroup comparisons were not significant. The acetylation index correlated positively (r = 0.922) with the ratio of glycine- to taurine-conjugated bile acids, measured independently, implying that it reflects this ratio.