Clinical factors associated with non-polypoid colonic adenomas ≥6 mm: a prospective study in an asymptomatic...

To examine the clinical factors associated with adenomas ≥6 mm presenting as non-polypoid polyps.

We conducted a prospective cross-sectional examination with a target population of consecutive asymptomatic patients presenting to a University endoscopy center for screening colonoscopy. Data, which included demographics, known colorectal cancer risk factors, and medications, were collected. One endoscopist using a high-definition wide-angle colonoscope performed all of the colonoscopies. Polyp morphology was classified according to the JRSC (Japanese Research Society for Cancer of Colon and Rectum) JRSC guidelines.

A total of 600 patients were screened and 150 adenomas ≥6 mm were detected. Of these 150 adenomas, 70 adenomas had a non-polypoid morphology while 80 were polypoid. Adenomas were more likely to present as non-polypoid in women as compared with men (adjusted odds ratio (AOR)=2.49; 95% confidence interval (CI)=1.08-5.75, P=0.03). Location of the adenoma in the proximal colon (AOR=4.21; 95% CI=1.83-9.71, P=0.001) and smoking (AOR=2.54; 95% CI=1.01-6.38, P=0.048) were independent predictors of flat morphology. In addition, advanced adenomas were also more likely to be flat in women (AOR=7.99; 95% CI=1.32-48.39, P=0.02) and proximal location was an independent predictor of flat morphology.

Adenomas ≥6 mm and advanced lesions were more likely to present as non-polypoid polyps in women when compared with men. Proximal location and smoking were also observed to be independent predictors of flat morphology.