Thin-layer chromatographic determination of urinary excretion of lactulose, simplified and applied to cystic fibrosis patients.

Urinary excretion of orally administered lactulose is used as an index of intestinal permeability. We have developed a simple thin-layer chromatographic technique for measuring lactulose in urine, using silica gel 60 plates and a propanol-borate solvent system. Lactulose concentrations as low as 62.5 mg/L can be detected with high reproducibility and without interference by urinary chromogens. After oral administration, the urinary excretion of lactulose in 8 h equaled 2.33 (SD 1.86)% in 15 patients with cystic fibrosis, as compared with 0.13 (SD 0.12)% in 16 healthy subjects (P less than 0.001).