Breath methane and colorectal cancer.

The association between colorectal cancer and breath methane is controversial. We compared a group of 59 patients with unresected colorectal cancer with a group of control subjects matched for age and sex. We also studied 43 of the cancer patients before and 3-6 months after resection. Sixty-three per cent of the patients with unresected carcinoma and 56% of the control subjects were methane excretors (NS). We found no significant change in methane excretion status after resection. Because recent colonic cleansing has been shown to influence methane production in the colon, 15 breath methane excretors were studied immediately before the start of cleansing, on the day of colonoscopy, and on the 7th day thereafter. Forty per cent became breath-methane-negative on the day of colonoscopy, but all 15 were excretors with a median of 60% of the precleansing concentration on the 7th day. The present study does not confirm an association between breath methane and colorectal cancer. It is unlikely that colonic cleansing procedures influenced the results of this study.