This study showed that MS increased the risk of having serrated lesions in the left colonic segments, while it did not affect the prevalence of adenomas. Analyzing each parameter of MS, our results showed that only patients with higher BMI had an increased risk of having adenomas, both in the right and left colonic segments. Furthermore, MS negatively affect the quality of bowel preparation.
Colorectal cancer represents a major cause of morbidity and mortality for both sex worldwide. Several studies analyzed the association between MS and cancer development [22]. In particular, MS was shown to be associated with colorectal cancer [12, 13, 23–25]. The association between these two conditions is particularly relevant due to the increasing incidence of MS in western countries in the last decades.
In a systematic review and meta-analysis of 17 studies by Esposito et al. [12], MS was associated with an increased risk of CRC incidence and mortality in both men (RR: 1.33, 95% CI 1.18–1.50, and 1.36, 1.25–1.48, respectively) and women (RR: 1.41, 1.18–1.70, and 1.16, 1.03–1.30, respectively). Furthermore, in a prospective study by Trabulo et al. [13] MS was shown to be significantly associated with an higher prevalence of adenomas (43% vs 25%, P = 0.004) and CRC (13% vs 5%, P = 0.027), compared with patients without MS. Moreover, MS was also a risk factor for synchronous (≥ 3) adenomas (35% vs 9%, P = 0.024) and sessile adenomas (69% vs 53%, P = 0.05), while no difference between location (P = 0.086), grade of dysplasia (P = 0.196), or size (P = 0.841) of adenomas. In a recent multicenter prospective study by Milano et al. [26], MS was significantly associated with both adenomas (OR: 1.76, 95% CI 1.54–2.00) and cancer (OR: 1.92, 95% CI 1.42–2.58) and it was the only risk factor associated with the presence of colonic lesions in patients younger than 50 years (OR 2.59, CI 95%: 1.78–3.79, P < 0.05). On the other hand, Koh et al. [27] in a retrospective study showed that, even if the prevalence of colon polyps was higher in the patients with higher triglyceride, BMI, and abdominal circumference, MS parameters were not statistically associated with the presence of PCL.
Secondly, the impact of MS on bowel cleansing was largely analyzed in literature and MS was shown to be inversely related with the quality of bowel preparation [16, 17], which is a relevant risk factor for missed adenomas and advanced adenomas in two meta-analyses [28, 29].
Our results confirm that bowel cleansing is negatively burdened by MS, although this data are limited by the suboptimal overall bowel cleansing in both groups. This was probably due to the low prevalence (46%) of “split dose” regimen preparation, which is the recommended bowel preparation according to ESGE guidelines [30]. Therefore, MS can negatively influence the protective role of colonoscopy in the detection and removal of premalignant lesions.