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Small intestinal bacterial overgrowth, intestinal permeability, and non-alcoholic steatohepatitis
  1. S M Riordan1,
  2. V M Duncombe1,
  3. M C Thomas1,
  4. A Nagree1,
  5. T D Bolin1,
  6. C J McIver2,
  7. R Williams3
  1. 1Gastrointestinal and Liver Unit, Prince of Wales Hospital, Sydney, Australia
  2. 2Department of Microbiology, Prince of Wales Hospital, Sydney, Australia
  3. 3Institute of Hepatology, University College London Medical School and Hospitals, London, UK
  1. Associate Professor S M Riordan, Gastrointestinal and Liver Unit, Prince of Wales Hospital, Barker Street, Randwick, 2031, NSW, Australia.
    riordans{at}sesahs.nsw.gov.au

https://doi.org/10.1136/gut.50.1.136-a

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    In a recent issue, Wigg and colleagues (Gut 2001;48:206–11) reported that small intestinal bacterial overgrowth (SIBO), as diagnosed by a combined 14C-d-xylose/lactulose breath test, is significantly more common in patients with non-alcoholic steatohepatitis (NASH) than in control subjects without liver disease. The authors investigated the possible pathogenic significance of this observation by examining whether intestinal permeability and circulating levels of endotoxin and tumour necrosis factor α are increased in NASH patients with SIBO compared with those without. No significant differences in any of these parameters could be demonstrated in the two groups.

    An important factor influencing the validity or otherwise of these findings is the diagnostic accuracy of the 14C-d-xylose and lactulose breath tests for SIBO. Our experience, using a sterile endoscopic technique to sample small intestinal secretions under direct vision, is that these breath tests lack sensitivity and specificity for culture proven SIBO.1,2 Endogenous CO2 production and colonic metabolism of d-xylose are important factors inherently limiting the accuracy of the 14C-d-xylose breath test for SIBO.1 Furthermore, reliance on the finding of “double peaks” in serial breath hydrogen or methane levels after ingestion of lactulose to improve the accuracy of the 14C-d-xylose breath test, or as a diagnostic marker in its own right, is problematic. In a study in which a scintigraphic tracer was administered concurrently with lactulose, we found that each of the double peaks in breath hydrogen values may occur after the arrival of the test meal at the caecum, paralleling delivery patterns of fermentable substrate to caecal bacteria. A caecal source of each peak was suggested on 50% of occasions, rather than the first peak necessarily reflecting small intestinal metabolism …

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