The Prevalence of Small Intestinal Bacterial Overgrowth in Patients with Non-Alcoholic Liver Diseases: NAFLD, NASH, Fibrosis, Cirrhosis—A Systematic Review, Meta-Analysis and Meta-Regression

Abstract

Bacterial overgrowth in the small intestine (SIBO) is a pathological growth of the intestinal microbiota in the small intestine that causes clinical symptoms and can lead to digestive and absorption disorders. There is increasing evidence that people with NAFLD have a distinct gut microflora profile as well metabolome changes compared to people without NAFLD. Thorough analysis of observational and RCT studies in the current databases (EMBASE, Web of Science, PubMed, Cinahl, Clinical Trials) was conducted from 3 November 2021 to 21 June 2022. The following inclusion criteria were applied: confirmed NAFLD, NASH, LIVER FIBROSIS, CIRRHOSIS due to steatosis; diagnostic methods of liver diseases—biopsy, elastography, transabdominal ultrasound; nonalcoholic fatty liver disease activity score; confirmed SIBO; diagnostic methods of SIBO–breath tests (hydrogen test; methane test and mix test; duodenal and jejunal aspiration before any type of intervention; adults above 18yo; number of participants ≥20; full articles. We excluded review articles, populations with HBV/HCV infection and alcohol etiology and interventions that may affect NAFLD or SIBO treatment. The quality of each study methodology was classified by means of the Cochrane Collaboration’s tool (RCT) and Newcastle—Ottawa Quality Assessment Scale adapted for cross-sectional, cohort and case-control studies. The random effects meta-analysis of outcomes for which ≥2 studies contributed data was conducted. The I2 index to measure heterogeneity and the ꭓ2 test of homogeneity (statistically significant heterogeneity p < 0.05) were applied. For categorical outcome, the pooled event rate (effect size) was calculated. This systematic review was reported according to PRISMA reporting guidelines. We initially identified 6643 studies, from which 18 studies were included in final meta-analysis. The total number of patients was 1263. Accepted SIBO diagnostic methods were both available breath tests (n-total = 15) and aspirate culture (n-total = 3). We found that among patients with non-alcoholic liver diseases, the random overall event rate of SIBO was 0.350 (95%CI, 0.244–0.472), p = 0.017. The subgroup analysis regarding a type of diagnosis revealed that the lowest ER was among patients who developed simultaneously NAFLD, NASH and fibrosis: 0.197 (95% CI, 0.054–0.510) as compared to other annotated subgroups. The highest prevalence of SIBO was observed in the NASH subgroup: 0.411 (95% CI, 0.219–0.634). There were no statistically significant differences in the prevalence of SIBO in different subgroups (p = 0.854). Statistically significant heterogeneity between studies was estimated (I2 = 86.17%, p = 0.00). Egger’s test did not indicate a publication bias (df = 16, p = 0.885). A meta-regression using a random-effects model revealed that higher percentage of males in the population with liver diseases is a predisposing factor toward SIBO (Q = 4.11, df = 1, p = 0.0426 with coefficient = 0.0195, SE = 0.0096, Z = 2.03). We showed that the prevalence of SIBO in patients with chronic non-alcoholic liver diseases can be as high as 35%, and it increases with the percentage of men in the population. The prevalence of SIBO does not differ significantly depending on the type of chronic liver disease. Despite the high heterogeneity and moderate and low quality of included studies, our meta-analysis suggests the existence of a problem of SIBO in the population of patients with non-alcoholic liver diseases, and the presence of SIBO, in turn, determines the therapeutic treatment of such type of patients, which indicates the need for further research in this area. The study protocol was registered with the international Prospective Register of Systematic Reviews (PROSPERO ID: CRD42022341473).

Novel Lauric Acid‐Butyric Structural Lipid Inhibits Inflammation: Small Intestinal Microbes May Be Important Mediators

“…The increase in small intestinal permeability and small intestinal microbial overgrowth may promote hepatic lipid accumulation and the development of inflammation. [31,32] Jang et al found that the small intestine protects the liver from fructose induced steatosis. [33] However, the important role of the small intestinal microbes in suppressing liver inflammation remains to be revealed.…”

Unravelling the controversy with small intestinal bacterial overgrowth

“…The odds for small intestinal bacterial overgrowth (SIBO) prevalence in patients with FD was significantly higher as compared to controls [4. [11,12] including systemic sclerosis [13], chronic liver disease [14] and Parkinson's disease. Three systematic reviews and meta-analyses have confirmed increased prevalence of SIBO in patients with chronic liver disease [14][15][16], irrespective of the aetiology of liver disease [15] and SIBO prevalence was significantly increased in patients with decompensated cirrhosis as compared to those with compensated cirrhosis [16], (50.5% vs. 31.2%; P < 0.001). Similarly, SIBO prevalence in is increased in patients with Parkinson's disease as compared to controls (OR ¼ 5.22, 95% CI 3.33-8.…”

“…Furthermore SIBO has been linked to several extra-intestinal disorders [11,12] including systemic sclerosis [13], chronic liver disease [14] and Parkinson's disease. Three systematic reviews and meta-analyses have confirmed increased prevalence of SIBO in patients with chronic liver disease [14–16], irrespective of the aetiology of liver disease [15] and SIBO prevalence was significantly increased in patients with decompensated cirrhosis as compared to those with compensated cirrhosis [16], (50.5% vs. 31.2%; P < 0.001). Similarly, SIBO prevalence in is increased in patients with Parkinson's disease as compared to controls (OR = 5.22, 95% CI 3.33–8.19), A recent meta-analysis [13], reported a 10-fold increased prevalence of SIBO in patients with systemic sclerosis as compared to controls, (OR = 9.6, 95% CI 5.6–16.5, P = 0.0001), with diarrhoea (OR = 5.9, 95% CI 2.9–16.0, P = 0.001) being associated with SIBO in patients with systemic sclerosis.…”

Understanding Our Tests: Hydrogen-Methane Breath Testing to Diagnose Small Intestinal Bacterial Overgrowth

“…( 99 ) Finally, we considered, but did not include, studies in patient populations rarely encountered in routine clinical practice, studies with significant heterogeneity, or studies where the reported association of SIBO was potentially confounded by additional variables (such as lifestyle, diet, and concurrent diseases) ( 100 – 109 ). Although a newer systematic review/meta-analysis on liver disease was available, the results of this analysis pooled all test modalities, and thus, we selected an older systematic review as the reference for SIBO prevalence for liver disease ( 110 ).…”