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Year : 2017  |  Volume : 8  |  Issue : 1  |  Page : 12-16

Colonoscopy does not induce small intestinal bacterial overgrowth

2ndMedical Department, “Iuliu Hatieganu” University of Medicine and Pharmacy, Cluj-Napoca, Romania

Date of Web Publication23-Mar-2017

Correspondence Address:
Dan Lucian Dumitraşcu
2nd Medical Department, Clinicilor Street, Number 3-5, Cluj-Napoca
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0976-5042.202813

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Background and Aim: Small intestinal bacterial overgrowth (SIBO) is associated with gastrointestinal pathology and colonoscopy. This endoscopic investigation could cause changes in gut flora including the occurrence of SIBO. We looked in this study for the effect of colonoscopy (preparation and intubation) on the occurrence of SIBO. Materials and Methods: Prospective study including thirty patients with irritable bowel syndrome (IBS) diagnosed according to Rome III criteria. Two groups were designed: Twenty IBS patients that performed colonoscopy (G1) and ten IBS patients (G2) not referred to colonoscopy. All patients have been tested for the presence of SIBO using glucose hydrogen breath tests (GHBT) at the beginning of the study, on day 1. G1 patients have also been tested before colonoscopy (day 2) and 1 week after (day 9). G2 patients performed GHBT on day 1 and on day 9. Results: The peak value of expired H2 was assessed, and the mean value was calculated. There were no significant statistical differences between the mean H2 values in the 2 groups of patients on day 1. The mean level of H2 significantly decreased after preparing for colonoscopy in G1 patients (P < 0.0001). There were no significant statistical differences between the mean levels of H2 on day 2 versus day 9 in G1 patients (P = 0.176). The mean level of H2 1 week after performing colonoscopy (7.65 ppm) is higher than that obtained after preparing for it (6.3 ppm), but no statistical significance. Patients from G2 showed no statistical differences between the mean levels of H2 on day 1 versus day 9 (P = 0.6132). Patients in G1 had a significantly lower mean H2 level versus G2 patients on day 9. Conclusions: Colonoscopy does not produce SIBO. Preparing for colonoscopy influences the level of expired H2, it reduces the number of intestinal bacteria, probably trough a mechanic effect or by inflating air during the procedure. Performing GHBT too soon after colonoscopy might result in false negative results of GHBT.

Keywords: Colonoscopy, H2 breath test, small intestinal bacterial overgrowth

How to cite this article:
Moraru IG, Dumitraşcu DL. Colonoscopy does not induce small intestinal bacterial overgrowth. J Dig Endosc 2017;8:12-6

How to cite this URL:
Moraru IG, Dumitraşcu DL. Colonoscopy does not induce small intestinal bacterial overgrowth. J Dig Endosc [serial online] 2017 [cited 2018 Apr 20];8:12-6. Available from: http://www.jdeonline.in/text.asp?2017/8/1/12/202813

  Introduction Top

Intestinal microbiota (microflora or intestinal flora) defines the complex microbian ecosystem located at the intestinal level.[1] Any qualitative or quantitative change in intestinal microbioma can have serious repercussions on humans. One of these changes is the appearance of small intestinal bacterial overgrowth (SIBO) syndrome.[2] SIBO is defined by the presence of ≥105 CFU/ml in the small bowel culture.[3]

The most common methods for diagnosing SIBO are represented by the hydrogen breath tests, using either lactulose or glucose.

Colonoscopy is an investigation frequently performed in patients who need testing for SIBO. Therefore, it is important to know if colonoscopy can influences SIBO status. It has been shown by several authors that preparing for colonoscopy significantly reduces the level of exhaled H2, modifying the H2-BT results.[4],[5] Performing H2-BT is usually recommended 4 weeks after colonoscopy, but studies on this subject have not yet established the time duration necessary for the intestinal flora to recover. It seems that preparing for colonoscopy reduces the number of intestinal bacteria.[5]


We looked in this study for the effect of colonoscopy on SIBO status in patients with IBS. We aimed to know if colonoscopy (preparation and intubation) is causing SIBO in IBS patients as we also looked for the effect of colon cleansing agent on SIBO status.

  Methods Top


We designed a prospective study of patients with IBS according to Rome III criteria.[6] Two groups were randomly created: A group of 20 IBS patients referred to colonoscopy (G1) and a group of 10 IBS patients (G2) not referred to colonoscopy. Any organic or biochemical diagnosis was ruled out according to a comprehensive work-out including previous colonoscopy, evaluation for malabsorption, hyperthyroidism, and any other confounding conditions. Demographic data of the subjects are displayed in [Table 1].
Table 1: Demographic data of the patients included in the study

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We have excluded from the study all patients with any organic disorder with similar symptoms or comorbidities: Intestinal tumors, inflammatory bowel disease, celiac disease, diabetes, and cirrhosis, intestinal, pancreatic, or gastric resections that could possibly lead to SIBO. We have also excluded patients that used in the last month drugs that interfere with intestinal motility (prokinetics, antispasmodic) or intestinal flora (antibiotics, probiotics).

All subjects included in the study signed an informed consent. The study was approved by the local ethics committee.


All 30 IBS patients included in the study were subjected for a glucose hydrogen breath test (GHBT) on day 1, at the base point. Patients have consequently been divided into two groups: G1 = 20 patients that, after performing GHBT, started preparing for colonoscopy using macrogol 4000–64 g/packet. They were submitted next day, day 2, in the morning, to colonoscopy. Just before performing the colonoscopy, all 20 patients have been submitted to another GHBT. One week after performing the colonoscopy, on day 9, GHBT was repeated again.

G2 included a number of 10 IBS patients that performed a GHBT on day 1 and 9. In this group, neither colon cleansing nor colonoscopy was performed [Figure 1].
Figure 1: IBS: Irritable bowel syndrome, GHBT: Glucose hydrogen breath test

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Glucose hydrogen breath test

According to the indications of the Rome Consensus group,[7] we have used in our study 50 g glucose in 250 ml water. The test was performed in the morning, on an empty stomach, after at least 1 day of carbohydrates free diet. Patients were asked not to smoke 2 h before the test and during the test,[8] not to chew gum or to perform any physical exercise,[5] all of the above being able to modify the level of breath H2. They were also asked to disinfect their mouth with chlorhexidine just before the test.

After a baseline sample of expired air, patients were asked to ingest substrate and breath sampled were analyzed at 15 min interval, for 120 min. If the baseline value of H2-BT is >16 ppm (parts per million), the patient is excluded from the study. The test is considered positive if there is a clear H2 peak, exceeding 20 ppm before the 120 min.

Preparation for colonoscopy

All 20 IBS patients included in G1, after performing GHBT, have started preparing for colonoscopy-4 packets of polyethylene glycol (PEG), macrogol 64 g/packet, 1 packet in 1 l water. Between 18 o'clock and 20 o'clock, patients were asked to drink 2 l water with 2 packets and between 2 o'clock and 4 o'clock, the rest. All colonoscopies were performed in the morning, starting at 10 o clocks, immediately after performing the day 2 GHBT. After performing colonoscopy 2 patients have been diagnosed with left colonic diverticulosis, 3 with megacolon and 1 patient presented 2 polyps of 3–4 mm; we performed endoscopic polypectomy in this case.


Statistical data processing and graphic representation of the results were been performed using Excel XLSTAT (from Microsoft Office 2007) application and Statistica 7 from STAT Soft Inc (Dell Statistica, 2300 East 14th Street Tulsa). Comparing group results has been performed using variant analysis, and the statistical significance of the contingency tables was been evaluated by means of Fischer or Chi-square test. P< 0.05 was considered significantly statistic. The significance threshold for the tests was set at P< 0.05 as statistical significant difference.

  Results Top

There were no significant statistical differences between patients included in the two groups (G1 and G2) regarding age, gender, and medium duration of symptoms [Table 1].

All patients have been divided into subgroups, according to the dominant IBS symptom, with no significant statistical difference between the numbers of patients in each subgroup [Figure 2].
Figure 2: G1-Group 1, G2-Group 2, IBS-C: Irritable bowel syndrome with constipation, IBS-D: Irritable bowel syndrome with diarrhea, IBS-M: Irritable bowel syndrome mixed symptoms, IBS-N: Irritable bowel syndrome unspecified symptoms

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All 30 IBS patients included in the study performed GHBT on day 1. For every patient, we have determined the peak value of breath H2, and we have calculated the mean value. There were no significant statistical differences between the mean H2 values, of the two groups of patients, G1 versus G2 on day 1 [Table 2].
Table 2: H2 level in day 1

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Among patients in the G1, 2 of them (10%) have been diagnosed with SIBO (H2 >20 ppm) and no patient from G2.

All 20 G1 patients, after performing GHBT, started preparing for colonoscopy using PEG 4 packets. The next morning (day 2) at 8 o clock, they performed another GHBT. The mean level of H2 after preparing for colonoscopy was significantly lower that the level noted before PEG ingestion (P< 0.0001) [Table 3]. No patient presented with SIBO after PEG administration.
Table 3: H2 level in day 1 versus day 2 in Group 1 patients

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All 20 G1 patients started performing colonoscopy at 10 AM in the morning. One week after colonoscopy, all patients, G1 and G2, performed another GHBT. Using post hoc analysis and variance analysis, we obtained significant statistical differences between the levels of H2 on day 1 versus day 9 (P< 0.0001), but no statistical differences between the levels of H2 on day 2 versus day 9 in G1 patients (P = 0.176) [Figure 3].
Figure 3: H2 mean level in G1 patients in day 1, day 2 and day 9. H2=Hydrogen, ***Very significant statistical difference, NS=No significant statistical difference

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The mean level of H2 1 week after performing colonoscopy (7.65 ppm) is higher than that obtained after preparing for it (6.3 ppm), but the difference has no statistical significance.

Regarding G2 patients, there were no statistical differences between the mean levels of H2 in day 1 versus day 9 (P = 0.6132) [Table 4].
Table 4: H2 level in day 1 versus day 9 in Group 2 patients

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Using variance analysis, there were significant statistical differences between the levels of H2 in G1 versus G2 in day 9, patients from G1 presenting a much lower H2 level [Table 5].
Table 5: H2 on day 9 in both groups

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  Discussions Top

IBS, one of the most frequently diagnosed functional gastrointestinal diseases all over the world, still represents a challenge in treatment and diagnosis.[9] SIBO was diagnosed in 4%–78%[10],[11],[12],[13],[14] of patients with IBS, making it a putative etiological factor.

Colonoscopy is indicated in almost all IBS patients. The effect of colon cleansing for colonoscopy and of the colonoscopy itself on the SIBO is still debated. More recently, same authors that used H2-BT to establish the quality of colon preparation for colonoscopy have underlined the decrease on H2 level after the preparation.[15]

Therefore we have performed a study on IBS patients that were evaluated by means of H2-BT and colonoscopy. In this study, we have obtained a significant reduction in exhaled H2 level after PEG ingestion (11.9 ppm vs. 6.3 ppm, P< 0.0001), data that correspond to those obtained by other authors. Recently, in a study from 2014, a group of Italian experts, has obtained the same H2 level reduction after preparing for colonoscopy (11 ± 1.8 ppm vs. 1.8 ± 0.3 ppm, P< 0.001).[15] Another study performed on 18 IBS patients, using lactulose BT, revealed the same H2 level reduction after preparing for colonoscopy (P< 0.05).[16]

Preparing for colonoscopy was performed with PEG, macrogol, with a medium molecular weight of 3350 Da. It is an osmotic laxative that does not determine absorption or secretion of electrolytes in the intestinal lumen and that due to his molecular weight is not absorbed in the intestines and is not digested by the intestinal flora. It acts by eliminating the fecal matters trough a mechanical effect, secondary to increasing their volume. The decrease in H2 level after PEG is probably due to his quantitative effect on the intestinal bacterial flora, reducing the number of bacteria, followed by a reduction in H2 level produced by those bacteria.[15],[16]

There were two patients in the G1 group diagnosed with SIBO (H2 level >20 ppm). After PEG ingestion, no patient presented with SIBO and a significant reduction in the H2 breath level was noted. H2-BT should not be performed immediately after preparing for colonoscopy to avoid their false negative results.

One week after colonoscopy all patients repeated GHBT, the level of H2 still being lower than the one found in day 1. The level is slightly elevated then the one in day 2 but the difference is not statistically significant, probably suggesting the beginning of the intestinal bacterial restore process. In our study, colonoscopy does not induce bacterial overgrowth. It seems that performing H2-BT 1 week after colonoscopy can result in false negative results, probably 4 weeks proposed by the Rome Consensus group [7] between the 2 investigations is reasonable, but more studies are still needed.

We have noted a significant difference between the levels of H2 on day 9 in the two groups G1 and G2 patients that performed colonoscopy, G1 showing a much-decreased level. It was suggested by some authors that inflating air during colonoscopy can reduce the number of intestinal anaerobe bacteria, consequently decreasing the level of H2.[17]

A limitation of our study is the relatively small sample; new studies, on larger patient populations, followed for a longer period to determine the changes in intestinal H2 level are needed.

  Conclusions Top

Colonoscopy does not induce SIBO. The level of exhaled H2 significantly decreases after preparing for colonoscopy (11.9 ppm vs. 6.3 ppm, P< 0.0001) and is maintained as such at least 1 week after colonoscopy. Performing H2-BT immediately after preparing for colonoscopy can result in false negative result for the H2-BT.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Young VB, Schmidt TM. Overview of the gastrointestinal microbiota. Adv Exp Med Biol 2008;635:29-40.  Back to cited text no. 1
Bures J, Cyrany J, Kohoutova D, Förstl M, Rejchrt S, Kvetina J, et al. Small intestinal bacterial overgrowth syndrome. World J Gastroenterol 2010;16:2978-90.  Back to cited text no. 2
Cole CR, Ziegler TR. Small bowel bacterial overgrowth: A negative factor in gut adaptation in pediatric SBS. Curr Gastroenterol Rep 2007;9:456-62.  Back to cited text no. 3
Thompson DG, Binfield P, De Belder A, O'Brien J, Warren S, Wilson M. Extra intestinal influences on exhaled breath hydrogen measurements during the investigation of gastrointestinal disease. Gut 1985;26:1349-52.  Back to cited text no. 4
Payne DL, Welsh JD, Claypool PL. Breath hydrogen (H2) response to carbohydrate malabsorption after exercise. J Lab Clin Med 1983;102:147-50.  Back to cited text no. 5
Drossman DA. Rome III: The new criteria. Chin J Dig Dis 2006;7:181-5.  Back to cited text no. 6
Gasbarrini A, Corazza GR, Gasbarrini G, Montalto M, Di Stefano M, Basilisco G, et al. Methodology and indications of H2-breath testing in gastrointestinal diseases: The Rome Consensus Conference. Aliment Pharmacol Ther 2009;29 Suppl 1:1-49.  Back to cited text no. 7
Rosenthal A, Solomons NW. Time-course of cigarette smoke contamination of clinical hydrogen breath-analysis tests. Clin Chem 1983;29:1980-1.  Back to cited text no. 8
Soares RL. Irritable bowel syndrome: A clinical review. World J Gastroenterol 2014;20:12144-60.  Back to cited text no. 9
Pimentel M, Chow EJ, Lin HC. Eradication of small intestinal bacterial overgrowth reduces symptoms of irritable bowel syndrome. Am J Gastroenterol 2000;95:3503-6.  Back to cited text no. 10
Grover M, Kanazawa M, Palsson OS, Chitkara DK, Gangarosa LM, Drossman DA, et al. Small intestinal bacterial overgrowth in irritable bowel syndrome: Association with colon motility, bowel symptoms, and psychological distress. Neurogastroenterol Motil 2008;20:998-1008.  Back to cited text no. 11
Chatterjee S, Park S, Low K, Kong Y, Pimentel M. The degree of breath methane production in IBS correlates with the severity of constipation. Am J Gastroenterol 2007;102:837-41.  Back to cited text no. 12
Moraru IG, Portincasa P, Moraru AG, Diculescu M, Dumitrascu DL. Small intestinal bacterial overgrowth produces symptoms in irritable bowel syndrome which are improved by rifaximin. A pilot study. Rom J Intern Med 2013;51:143-7.  Back to cited text no. 13
Moraru IG, Moraru AG, Andrei M, Iordache T, Drug V, Diculescu M, et al. Small intestinal bacterial overgrowth is associated to symptoms in irritable bowel syndrome. Evidence from a multicentre study in Romania. Rom J Intern Med 2014;52:143-50.  Back to cited text no. 14
Altomare DF, Bonfrate L, Krawczyk M, Lammert F, Caputi-Jambrenghi O, Rizzi S, et al. The inulin hydrogen breath test predicts the quality of colonic preparation. Surg Endosc 2014;28:1579-87.  Back to cited text no. 15
Gilat T, Ben Hur H, Gelman-Malachi E, Terdiman R, Peled Y. Alterations of the colonic flora and their effect on the hydrogen breath test. Gut 1978;19:602-5.  Back to cited text no. 16
Thompson DG, O'Brien JD, Hardie JM. Influence of the oropharyngeal microflora on the measurement of exhaled breath hydrogen. Gastroenterology 1986;91:853-60.  Back to cited text no. 17


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]


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