Colon cells from patients with ulcerative colitis utilize short-chain fatty acids inefficiently and may be exposed to decreased concentrations of these compounds. To test whether irrigation of the inflamed mucosa with short-chain fatty acids is useful, we conducted a six-week preliminary trial in 12 patients with distal colitis. Each patient used twice daily rectal irrigations with 100 ml of a solution containing acetate (80 mM), propionate (30 mM), and butyrate (40 mM). Two patients stopped at three weeks, one because of no improvement and the other because of complete resolution of symptoms. Of the 10 who completed the trial, nine were judged to be at least much improved and showed a change in a mean disease activity index score from 7.9 +/- 0.3 (SE) to 1.8 +/- 0.6 (SE) (P less than or equal to 0.002) and in a mucosal histology score from 7.7 +/- 0.7 (SE) to 2.6 +/- 0.7 (SE) (P less than or equal to 0.002). Thus, ulcerative colitis patients appear to benefit from increased contact with or higher than usual levels of these critical energy substrates.