Background: In patients with long-standing ulcerative colitis (UC), current dysplasia surveillance guidelines recommend four-quadrant biopsies every 10 cm throughout the colon. However, this may be inefficient if neoplastic lesions are localized in particular segments of the colorectum. The aim was to determine whether a difference exists in the anatomic distribution of dysplasia discovered in UC patients undergoing colonoscopic surveillance.

Methods: From an institutional database of over 700 patients with UC who underwent two or more surveillance colonoscopies between 1994-2006, we identified all patients with flat (endoscopically invisible) low-grade dysplasia (fLGD) or advanced neoplasia (colorectal cancer [CRC] or high-grade dysplasia [HGD]). Pathology reports were reviewed regarding the anatomic location of all dysplastic lesions. Fisher's exact test was used to compare the frequencies of neoplasia among the different colonic segments.

Results: We identified 103 patients who progressed to any neoplasia (fLGD, HGD, or CRC). These patients underwent a total of 396 colonoscopies. The mean age at first surveillance colonoscopy was 48.6 years, with a mean UC disease duration of 18.2 years; 100% had extensive disease. Fifty-five patients developed advanced neoplasia. The rectosigmoid was found to have a significantly greater number of biopsies positive for advanced neoplasia and for any neoplasia compared to all other colonic segments (P < 0.0007); 71.2% of all advanced neoplasia was in the rectosigmoid.

Conclusions: The majority of dysplastic lesions identified in a surveillance program was detected in the rectosigmoid. Endoscopists should consider taking a greater percentage of biopsies in these segments as opposed to more proximal areas.