Abstract
Background Colorectal cancers (CRC) have been suggested to be involved with coliform bacteria, while the association with small intestinal bacteria is not clear. The study objective was to investigate the relationship between patients with CRC and the gas production characteristics of small intestinal bacteria using the lactulose breath test (LBT).Methods Data on age, gender, body mass index (BMI), hydrogen and methane concentrations at various time points, and colonoscopy results of patients with bowel diseases were collected from 2017 through 2023. The gas production characteristics of small intestinal bacteria were analyzed in patients with functional and organic bowel diseases, particularly in those patients with polyps and CRC. Additionally, receiver operating characteristic (ROC) analysis was performed to differentiate between these conditions.Results A total of 274 patients with functional bowel diseases, 274 patients with organic bowel diseases, 214 patients with polyps, and 18 patients with CRC were included. Methane concentrations in patients with organic bowel diseases, whether polyps or CRC, were significantly higher than in those with functional bowel diseases. Conversely, hydrogen concentrations were significantly higher in patients with functional bowel diseases compared to those with organic bowel diseases and polyps at certain time points. The area under the curve (AUC) for the methane concentrations at the 60-minute mark in predicting CRC was 0.7104 (95% confidence interval, 0.6166–0.8042). Among patients with CRC, hydrogen concentrations were significantly higher in those with CRC compared to those with polyps.Conclusions There were distinct features of hydrogen and methane production in patients with organic bowel diseases compared to those with functional bowel diseases. Patients with CRC or polyps exhibited higher methane concentrations. Additionally, the LBT appears to be a promising tool for distinguishing functional bowel diseases and CRC.