Increased urinary excretion of iohexol after enteral administration in patients with ileal Crohn's disease. A new test for disease activity.

Iohexol is a water-soluble contrast medium that is partly absorbed/permeated through mucosa of the small bowel and excreted unchanged in the urine. Iohexol was administered orally to 12 patients with Crohn's disease of the ileum and to 10 healthy controls to measure its excretion in the urine. The location and activity of Crohn's disease were determined by barium double-contrast radiography in all patients and by ileoscopy and biopsy in 9 patients. Iohexol concentrations in serum and 24-hour urine were measured using reversed phase high-performance liquid chromatography. Urinary excretion of iohexol was significantly greater in patients with active Crohn's disease than in controls. We suggest this method as a new way of measuring Crohn's disease activity and mucosal damage in the small bowel. Bowel inflammation and mucosal cell damage are strongly indicated if the iohexol excreted in the urine is over 1% of the oral intake.