Menthol Spray Boosts Detection Rate of Polyps

Spraying the colon with L-menthol—an organic compound found in peppermint oil—improves adenoma detection rate during colonoscopy, according to a new study.

Researchers at the University of Western Ontario (UWO; London, Canada) conducted a randomized, placebo-controlled trial at Kyoto Prefectural University (Japan) involving 226 patients (118 study cohort, 108 controls). An 8 mL volume of peppermint oil and 0.2 mL of polysorbate were gently mixed and dissolved in 500 mL of distilled water to manufacture L-menthol. The placebo used was water and dimethicone. All procedures were performed by one of three colonoscopists who had performed over 1,000 procedures.

In each case, the colonoscope was inserted as far as the cecum, and placebo or L-menthol was then directly and gently sprayed onto the cecum through the working channel of the endoscope. At that time, endoscopic evaluation of colon was initiated. The results showed that the adenoma detection rate was 42.6% among the placebo-treated patients and 60.2% in the menthol treated patients. In addition to increasing the detection rate, using the L-menthol spray also appeared to suppress gastric peristalsis, which can adversely impact colonoscopy.

The researchers suggest that the antiperistalsis effects of L-menthol are partly responsible for the improve polyp detection. In addition to the low-grade polyp detection, patients who were treated with L-menthol also had more high-grade or cancerous lesions observed during the colonoscopy. There were 13 precancerous or cancerous lesions found among the patients in which menthol was used, compared with 7 such lesions among the placebo-treated patients. The study was presented at Digestive Disease Week (DDW), held during May 2014 in Chicago (IL, USA).

"We were very happy to discover that the adenoma detection rate in the L-menthol group was significantly [greater] by almost 20%. In addition to increasing the detection rate, using the L-menthol spray also appears to suppress gastric peristalsis, which can adversely impact colonoscopy,” said lead author and study presenter Ken Inoue, MD, PhD. “30.9% of placebo patients were free of peristalsis, compared with 71.2% of those patients who underwent colonoscopy using the menthol spray.”

Peristalsis is a radial, symmetrical contraction and relaxation of muscles which propagates a wave motion in an anterograde fashion. The circular smooth muscles in the gastrointestinal (GI) tract contract in sequence to produce a peristaltic wave, followed by a contraction of longitudinal smooth muscles which pushes the digested food forward.

Related Links:
University of Western Ontario
Kyoto Prefectural University