Increased urinary nitrite, a marker of nitric oxide, in active inflammatory bowel disease

BACKGROUND: Nitric oxide (NO) production is increased in inflammatory bowel disease (IBD), and measurement of NO metabolites may be useful for monitor ing disease activity. Aims and objectives: To characterise urinary nitrite levels, a stable metab olite of NO, in IBD and to evaluate its potential as a marker of disease ac tivity. Methods: Twelve-hour urinary nitrites were measured by the microplate assay method in 46 patients with IBD (active; n = 32). Urinary samples from 16 h ealthy individuals served as controls. Results: Increased levels of urinary nitrites were found in patients with a ctive IBD compared with those with inactive IBD. Twenty-eight out of 32 pat ients (87.5%) with active IBD had detectable levels of nitrite in their uri ne as compared with 2/14 (14.3%) patients with inactive IBD. None of the 16 healthy controls had detectable urinary nitrite. Twelve-hour urinary nitri te in active compared with inactive IBD: 5 (I) over bar 0.7 versus 0.1 (I) over bar 0.04 mu mol (P < 0.05). There was good correlation between urinary nitrite and some markers of disease activity in IBD such as C-reactive pro tein and microalbuminuria but not with erythrocyte sedimentation rate. Conclusions: Increased levels of nitrite were detected in urine of patients with active IBD, consistent with increased NO synthesis. This simple assay may be exploited as a potential marker of disease activity in IBD.