Simethicone with polyethylene glycol improves bowel cleanliness, polyp detection

Adding the antifoaming agent simethicone to the bowel preparation regimen leads to improvement in bowel cleanliness quality and detection rate of polyps (PDR) but not adenomas (ADR), reports a recent study. There are no statistically significant differences seen in withdrawal time, cecal intubation time, and cecal intubation rate.

“Besides, we found that simethicone improved the detection rate of lesions in the right colon and decreased abdominal bloating but had no effect on vomiting and abdominal pain or cramping,” the researchers said.

The databases of PubMed, Embase, and Web of Science were searched manually and electronically for studies published before 1 February 2020. The quality of bowel preparation and the ADR and PDR were the primary outcomes. The researchers used a pooled estimate of risk ratio and a random-effect model to calculate all data.

Eighteen randomized controlled trials (RCTs) including a total of 7,187 patients met the eligibility criteria for the meta-analysis. Simethicone added to polyethylene glycol (PEG) improved colon cleansing (p<0.00001), PDR (p=0.006), and the detection rate of lesions in the right colon (p<0.00001) as compared with PEG alone. [J Clin Gastroenterol 2021;55:e46-e55]

No between-group differences were found in ADR (p=0.68), withdrawal time (p=0.06), cecal intubation rate (p=0.98), and cecal intubation time (p=0.65). The PEG group showed a higher rate of abdominal bloating, but no significant differences were noted in vomiting (p=0.65) and abdominal pain (p=0.25).

“The underlying mechanism of simethicone in improving bowel cleansing is still unknown,” the researchers said. “Apart from reducing the surface tension of the intestinal contents, simethicone may potentially decrease the resistance from bubbles, thereby promoting intestinal peristalsis.” [Endoscopy 2018;50:412-422]

Furthermore, the current study reported a significant association between colonoscopy interval and bowel cleansing. In three articles that compared the preparations to colonoscopy interval, the optimal interval needed to achieve adequate bowel cleansing was found to be between 2 and 7 hours. In contrast, the risk of inadequate cleansing increased if colonoscopy was performed after 7 hours.

“Colonoscopy is the most direct way to diagnose and treat colorectal diseases, but it has a certain rate of missed diagnosis of lesions, especially in the right colon,” the researchers said. [Ann Intern Med 2011;154:22-30]

“Because of the deep fold of the right colon, the lesions are often flat, resulting in a higher rate of missed diagnosis. Therefore, it is of great clinical significance to reduce the missed diagnosis of polypoid lesions in the right colon,” they added.

A study by Zhang and colleagues demonstrated that ADR in the right colon was significantly higher for the simethicone group than the conventional group. In the current meta-analysis, simethicone reduced mucus or bubbles, produced a clearer field of vision, and increased the detection rate of right colonic polyps, which could improve the effectiveness of colonoscopy. [Endoscopy 2018;50:412-422]

 “More large double-blinded multicentre RCTs are necessary to evaluate the potential effect of simethicone on colonoscopy,” the researchers said.