The widespread adoption of colonoscopy screenings has led to rapid decreases in colorectal cancer (CRC) incidence and mortality in the last 20 years. Early detection and prevention with colonoscopies are more effective than other tests such as sigmoidoscopy, guaiac-based fecal occult blood testing, and fecal immunochemical tests.
Nevertheless, CRC is still the second leading cause of cancer deaths —after lung cancer —worldwide. The World Health Organization reported 1,930,000 new cases and 935,000 deaths in 2020. CRC is shifting to diagnosis at a more advanced stage and a younger age.
High-quality screening and treatment among all populations is crucial to improving the numbers. The bowel prep required for colonoscopy entails clearing the bowel with liters of laxative solutions, a procedure which — besides being extremely unpleasant— negatively alters the gut microbiota. In addition, patients frequently report diarrhea, constipation, abdominal pain, bloating, and other adverse effects for days or weeks after bowel prep and colonoscopy. Ameliorating these notorious side effects may lead to a higher number of individuals opting for regular screening colonoscopies.
The relationship between dysbiosis and colonoscopy is being explored. Researchers have recently evaluated the effect of probiotics on gastrointestinal symptoms and microbiome modulations in patients undergoing colonoscopy.
Bowel prep and gut microbiota
Bowel preparation (lavage) requires the consumption of liters of sulfate, sodium phosphate, or polyethylene glycol solutions. Water then passes into the intestinal lumen and flushes fecal residues.
Several studies have explored whether these preparations significantly affect the composition of gut microbiota:
- A randomized control trial with 23 healthy subjects observed an instant and substantial change in gut microbiota after a bowel cleanse. Both single and double doses of a bowel preparation significantly altered the microbiota, with the single dose showing a more severe effect. The restoration of bacterial levels and composition occurred within 14 days, but the recovery rate was dose-dependent, and certain bacterial groups were notably increased after purging.
- In an early study, changes in the fecal microbiota were examined in five individuals undergoing screening colonoscopy. In three of the five subjects, microbial composition profiles were different in stool samples collected after the colonoscopy compared to stool collected before the colonoscopy.
- Another small study examined 12 healthy individuals divided into three groups. All groups underwent baseline un-prepped flexible sigmoidoscopies with biopsies. The experimental group then received a standard bowel cleanser, with the control groups receiving none. After sigmoidoscopies, results showed that bowel preparation altered the diversity of mucosa-associated microbiota.
The persistence of these changes has also been studied:
- In fifteen subjects undergoing bowel cleanse, short-term changes in fecal microbiota were observed but there was no lasting effect on the majority of subjects.
- A study of 23 subjects found that although the microbiota composition was affected immediately after lavage, the unique composition and total bacterial load returned to baseline levels after 14 days.
- The rapid recovery was confirmed in a 2019 study that analyzed 70 fecal samples (24 from the bowel prep group and 46 from the control group). Moreover, 32 metabolites exhibited significant changes before and immediately after the preparation, but these metabolites also returned to their original levels within 14 days.
- On the other hand, an enduring impact was observed in the fecal samples of 10 patients one month following bowel cleansing. The composition of the microbiota changed, marked by a decrease in the abundance of lactobacilli, a beneficial bacterial population.
Gut microbiota changes and adverse effects
Intestinal microbiome changes following bowel lavage and colonoscopy may be contributing to the common abdominal symptoms observed in these patients. For example, in patients with ulcerative colitis, bowel prep and colonoscopy are linked to a worsening of symptoms, thought to be possibly related to alterations in beneficial microbes. Moreover, there is evidence demonstrating that patients who undergo a colonoscopy have an increased susceptibility to developing appendicitis within one week. Although the risk is relatively low, it is worth investigating any potential associations with microbial changes.
Several studies suggest that probiotics may both alleviate side effects arising from bowel preparation followed by colonoscopy and improve intestinal dysbiosis.
- In a small 2020 clinical study, a multispecies probiotic preparation was associated with restored intestinal microbial diversity in addition to a reduced abundance of pathogens.
- Another trial, with a large outpatient group, found that a probiotic mixture administered for four weeks after colonoscopy was linked to the reduced occurrence and severity of intestinal symptoms and improved stool form.
- In a study comparing the effect of probiotics in 133 patients compared to 126 patients receiving a placebo, the group receiving probiotics reported fewer days in pain after colonoscopy.
- And in a 2023 multicenter clinical trial, a multispecies probiotic formulation (Bifidobacterium bifidum, Bifidobacterium lactis, Enterococcus faecium, Lactobacillus acidophilus, Lacticaseibacillus rhamnosus, and Lactococcus lactis) administered for 30 days showed a significant reduction in days with constipation and a trend towards reduced days with pain, bloating and diarrhea after colonoscopy in the probiotic treated group. The researchers suggested, “that the gastrointestinal tract cleaning never removes all bacteria and that beneficial probiotic taxa might remain at the mucosa and are therefore faster to prevent side effects.”
- And finally, in a different approach, a recent study provided probiotics (26 patients) or a placebo (25 patients) for one month before colonoscopy. Results showed that “pretreatment probiotics had benefits on the alteration and recovery of gut microbiota and possible complications after bowel preparation.”
Colonoscopy remains the gold standard in early detection and prevention of colorectal cancer. However, the required bowel preparation is a distasteful barrier to the full adoption of the procedure. Cleaning of the intestinal mucosa alters the gut microbiome significantly. While there is some conflicting data, long-term changes are not generally seen. Short-term changes may also contribute to common abdominal symptoms including bloating, pain, diarrhea, or constipation.
Several studies suggest that probiotic administration may both alleviate side effects arising from bowel preparation followed by colonoscopy and improve intestinal dysbiosis. Therefore, probiotics may improve tolerance of this life-saving procedure.
Basson, Marc D et al. “Association of Colonoscopy With Risk of Appendicitis.” JAMA surgery vol. 153,1 (2018): 90-91. doi:10.1001/jamasurg.2017.3790
Bonavina, Luigi et al. “Lactobacillus plantarum LP01, Lactobacillus lactis subspecies cremoris LLC02, and Lactobacillus delbrueckii LDD01) in patients undergoing bowel preparation.” Acta bio-medica : Atenei Parmensis vol. 90,7-S 13-17. 10 Jul. 2019, doi:10.23750/abm.v90i7-S.8650
Chen, Hui-Mei et al. “Gut microbiome changes in overweight male adults following bowel preparation.” BMC genomics vol. 19,Suppl 10 904. 31 Dec. 2018, doi:10.1186/s12864-018-5285-6
Deng, Xiaorong et al. “Oral Probiotics Alleviate Intestinal Dysbacteriosis for People Receiving Bowel Preparation.” Frontiers in medicine vol. 7 73. 28 Feb. 2020, doi:10.3389/fmed.2020.00073
Drago, Lorenzo et al. “Persisting changes of intestinal microbiota after bowel lavage and colonoscopy.” European journal of gastroenterology & hepatology vol. 28,5 (2016): 532-7. doi:10.1097/MEG.0000000000000581
D’Souza, Basil et al. “Randomized controlled trial of probiotics after colonoscopy.” ANZ journal of surgery vol. 87,9 (2017): E65-E69. doi:10.1111/ans.13225
Harrell, Laura et al. “Standard colonic lavage alters the natural state of mucosal-associated microbiota in the human colon.” PloS one vol. 7,2 (2012): e32545. doi:10.1371/journal.pone.0032545
Jalanka, Jonna et al. “Effects of bowel cleansing on the intestinal microbiota.” Gut vol. 64,10 (2015): 1562-8. doi:10.1136/gutjnl-2014-307240
Labenz, Joachim et al. “Application of a multispecies probiotic reduces gastro-intestinal discomfort and induces microbial changes after colonoscopy.” Frontiers in oncology vol. 12 1078315. 9 Jan. 2023, doi:10.3389/fonc.2022.1078315
Mai, V et al. “Effect of bowel preparation and colonoscopy on post-procedure intestinal microbiota composition.” Gut vol. 55,12 (2006): 1822-3. doi:10.1136/gut.2006.108266
Menees, Stacy et al. “Does colonoscopy cause increased ulcerative colitis symptoms?.” Inflammatory bowel diseases vol. 13,1 (2007): 12-8. doi:10.1002/ibd.20049
Nagata, Naoyoshi et al. “Effects of bowel preparation on the human gut microbiome and metabolome.” Scientific reports vol. 9,1 4042. 11 Mar. 2019, doi:10.1038/s41598-019-40182-9
O’Brien, Claire L et al. “Impact of colonoscopy bowel preparation on intestinal microbiota.” PloS one vol. 8,5 e62815. 1 May. 2013, doi:10.1371/journal.pone.0062815
Scott, Karen P et al. “Prebiotic stimulation of human colonic butyrate-producing bacteria and bifidobacteria, in vitro.” FEMS microbiology ecology vol. 87,1 (2014): 30-40. doi:10.1111/1574-6941.12186
Siegel, Rebecca L et al. “Colorectal cancer statistics, 2023.” CA: a cancer journal for clinicians vol. 73,3 (2023): 233-254. doi:10.3322/caac.21772
Son, Dooheon et al. “Benefits of Probiotic Pretreatment on the Gut Microbiota and Minor Complications after Bowel Preparation for Colonoscopy: A Randomized Double-Blind, Placebo-Controlled Pilot Trial.” Nutrients vol. 15,5 1141. 24 Feb. 2023, doi:10.3390/nu15051141
Steffenssen, Mia W et al. “Patient-reported minor adverse events after colonoscopy: a systematic review.” Acta oncologica (Stockholm, Sweden) vol. 58,sup1 (2019): S22-S28. doi:10.1080/0284186X.2019.1574979