Background Intestinal gases are produced via bacterial fermentation or cell metabolism, which can reveal altered intestinal microbiota and abnormal inflammation responses. The significance of jointly detecting multiple intestinal gases in the fasting state has attracted increased attention. This study intends to explore the alterations of hydrogen (H₂), methane (CH₄), hydrogen sulfide (H₂S), and nitric oxide (NO) via breath tests in the fasting state in patients with UC, to evaluate the potential value of intestinal gases.

Methods 51 patients with active UC and 83 healthy volunteers were enrolled to collect clinical data and complete breath tests for H₂, CH₄, H₂S, and NO in the fasting state through the Sunvou-CA4458+H2S gas analysis detector manufactured by Sunvou Medical Electronics Company Limited.

Results A decrease in H₂ and an increase in H₂S and NO were observed in UC patients compared with healthy volunteers. With the cut-off value ≥5.5ppb, the sensitivity and specificity of exhaled NO in distinguishing UC patients from healthy volunteers were 74.5% and 68.7%. The exhaled H₂ and NO were related to the clinical manifestations of patients with UC. Patients with distinct clinical symptoms had decreased H₂ and increased NO. H₂ was correlated with the abundance of Gram-positive bacilli in fecal smears. Patients with large amounts of Gram-positive bacilli in fecal smears had increased H₂. NO was correlated with the disease activity of UC. Patients with moderate or severe disease, according to Truelove and Witts classification, had increased NO compared with those with mild disease. NO was significantly associated with total Mayo score (r=0.3262, P < 0.01), UC endoscopic index of severity (r=0.3262, P < 0.01), simple clinical colitis activity index (r=0.3973, P < 0.0001), and clinical activity index (r=0.2942, P < 0.01).

Conclusions Patients with UC had an altered gas metabolism. The alterations were closely related to the clinical characteristics and disease activity and reflected the alterations of intestinal flora and intestinal inflammation in patients with UC to a certain extent. Intestinal gases have potential application value in the diagnosis and management of UC and are worthy of further study.