Findings in the distal and proximal colon in colonoscopy screening after positive fecal immunological test and related pre-procedure factors

Abstract

Background: colonoscopy is the gold standard method for the early diagnosis and prevention of colorectal cancer (CRC). Screening programs include immune determination of blood in feces. Regardless of the method used, proximal colon lesions appear to be detected less frequently. Objective: to analyze the characteristics of proximal and distal lesions and possible predisposing factors. Methods: a cross-sectional study was performed of 692 patients from the CRC screening program with fecal immunological test (FIT) ≥ 100 ngHb/ml (October 2017-October 2018). The right colon was examined twice as patients were participating in a randomized clinical trial to re-evaluate the right colon by forward-viewing endoscope or proximal retroflexion. The adenoma detection rate (ADR), advanced neoplasia (AN) and CRC in the proximal and distal colon, histological and morphological characteristics in each section were analyzed. Results: in the study, 52.9 % of the patients were male, with a mean age of 59.5 years (standard deviation [SD]: 7.6); 1,490 polyps were found and the ADR was 57.7 % (distal 42 % and proximal 37 %). Detection rates were 45.8 % for AN, 40.9 % for advanced adenomas, 5.2 % for advanced sessile serrated lesions (SSL) and CRC was diagnosed in 4.8 % of patients. Males had more AN than females. The mean age of patients with AN was significantly higher. AN were associated with smoking and alcohol consumption (p = 0.0001). Globally, FIT levels were higher in patients with AN (p = 0.003). Sixty-six per cent of cancers were distally located and 61.3 % of CRC were diagnosed in the early stages. Conclusions: in an average-risk asymptomatic population undergoing colonoscopy after positive FIT, AN were more common in the distal colon in males, older patients, smokers and those with alcohol intake.