The Long-term Impact of Roux-en-Y Gastric Bypass on Colorectal Polyp Formation and Relation to Weight Loss Outcomes.

BACKGROUND

Evolving epidemiological data, backed by mechanistic evidence, supports a paradoxical increase in the risk of colorectal cancer after Roux-en-Y gastric bypass surgery (RYGB). We examined the risk of colonic polyps after RYGB.

METHODS

A single-center retrospective study included colonoscopies performed between the years 1994 and 2018. To focus on the long-term impact of RYGB on precancerous colonic polyps, we compared patients at average risk for CRC who underwent colonoscopy ≥ 5 years after RYGB (n = 86) versus pre-RYGB (n = 106). We analyzed our data using inverse probability of treatment weighting (IPTW) using propensity scores in order to account for multiple potential confounders.

RESULTS

After IPTW, we found no statistical differences between pre- and post-RYGB patients for risk of any polyp (33.2% pre- vs. 32.7% post-RYGB). However, the percentage of serrated polyps was higher ≥ 5 years post-RYGB compared with pre-RYGB (8.7% vs. 2.1%, p = 0.04, relative risk = 4.22; 95% CI 0.97, 18.4). Body mass index ≥ 30 kg/m2 at time of colonoscopy was associated with a greater risk for any polyp after RYGB (OR 6.23; 95% CI 1.16, 33.41). There was also a trend towards increased risk of polyps in post-RYGB patients who were current smokers (OR = 4.97; 95% CI 0.82, 30) or with age > 55 years (OR = 2.49; 95% CI 0.88, 7.00).

CONCLUSION

Our data suggest that RYGB is associated with an increased risk of serrated polyps after 5 years from surgery. Prospective studies defining this risk and examining mechanisms will be instrumental for application of CRC preventative strategies in this population.