Antonio Missanelli

Absorbable vs. non‐absorbable antibiotics in the treatment of small intestine bacterial overgrowth in patients with blind‐loop syndrome

Background : Small intestine bacterial overgrowth is associated with the presence of predisposing conditions, acting through different mechanisms. Therefore, the failure to define a standardized therapy may be due to a methodological bias: to treat a condition characterized by different pathophysiological mechanisms with the same pharmacological approach. Non‐absorbable antibiotics could have a lower efficacy than absorbable drugs in patients with blind loops which exclude a portion of the intestine from the transit.

Meal induced rectosigmoid tone modification: a low caloric meal accurately separates functional and organic gastrointestinal disease patients

Background and aims: Diagnosis of irritable bowel syndrome (IBS) is based on arbitrary criteria due to the lack of an accurate diagnostic test. The aim of this study was to evaluate whether rectosigmoid tone modification after a meal represents an accurate diagnostic approach. Methods: In a secondary care setting, 32 constipation predominant and 24 diarrhoea predominant IBS patients, 10 functional diarrhoea and 10 functional constipation patients, 29 organic gastrointestinal disease patients, and 10 healthy volunteers underwent a rectal barostat test to measure fasting and postprandial rectosigmoid tone. Rectosigmoid response was assessed following three meals containing different amounts of calories: 200 kcal, 400 kcal and 1000 kcal. Results: After 200 kcal, healthy volunteers and patients with organic diseases showed a reduction in rectosigmoid volume of at least 28% of fasting volume, indicating a meal induced increase in muscle tone. In contrast, patients with diarrhoea predominant IBS showed dilation of the rectosigmoid colon, indicative of reduced tone, and patients with constipation predominant IBS showed a mild volume reduction or no modification. Functional diarrhoea and constipation patients showed rectosigmoid tone modification resembling that of the corresponding IBS subtype. A 400 kcal meal normalised rectosigmoid tone in more than half of the constipation predominant IBS patients but none of the diarrhoea predominant IBS patients. In contrast, a 1000 kcal meal normalised tone response in all IBS patients. Sensitivity of the test was 100%, specificity 93%, positive predictive value 96%, and negative predictive value 100%. Conclusion: A postprandial reduction in rectosigmoid tone of at least 28% of fasting value after a low caloric meal accurately separates organic and functional gastrointestinal disease patients. This parameter may therefore be used in the positive diagnosis of IBS.

Mixing of the intestinal content and variations of fermentation capacity do not affect the results of hydrogen breath test.

OBJECTIVES:Although the hydrogen (H2) breath test has been in use for many years for diagnosis of sugar malabsorption, research is still underway to improve its diagnostic accuracy. In this study, we investigated whether possible confusing factors caused by the ingestion of the test solution itself (such as the delivery to the colon of other fermentable substrates pre-existing in the small bowel lumen, the release of preformed H2 trapped in the feces, or differences in the fermenting capacity of the colonic bacteria) may interfere with the increase of breath H2 concentration, an expression of malabsorption of the test substrate.METHODS:In 25 patients with untreated celiac disease and 23 sex- and age-matched healthy volunteers, breath H2 excretion was measured after ingestion of a 250-ml solution containing sorbitol, a poorly absorbed alcohol sugar. On 2 other separate days, 12 randomly selected subjects in each group underwent breath H2 excretion measurement after ingestion of 250 ml of a sugar free, nonabsorbable electrolyte solution and 250 ml of a solution containing lactulose, a nonabsorbable disaccharide.RESULTS:After sorbitol ingestion, celiac disease patients showed a significantly higher breath H2 excretion than did healthy volunteers. Otherwise, breath H2 responses to electrolyte solution and lactulose showed no difference between the two groups of subjects.CONCLUSIONS:In a group of patients with sugar malabsorption, increased breath H2 excretion does reflect malabsorption. The washout or the mixing of the intestinal content or intergroup difference of fermenting activity of the colonic bacteria do not represent interfering factors and do not modify the accuracy of the H2 breath test in day-to-day clinical practice.

Original contributionMixing of the intestinal content and variations of fermentation capacity do not affect the results of hydrogen breath test

Abstract Objectives Although the hydrogen (H2) breath test has been in use for many years for diagnosis of sugar malabsorption, research is still underway to improve its diagnostic accuracy. In this study, we investigated whether possible confusing factors caused by the ingestion of the test solution itself (such as the delivery to the colon of other fermentable substrates pre-existing in the small bowel lumen, the release of preformed H2 trapped in the feces, or differences in the fermenting capacity of the colonic bacteria) may interfere with the increase of breath H2 concentration, an expression of malabsorption of the test substrate. Methods In 25 patients with untreated celiac disease and 23 sex- and age-matched healthy volunteers, breath H2 excretion was measured after ingestion of a 250-ml solution containing sorbitol, a poorly absorbed alcohol sugar. On 2 other separate days, 12 randomly selected subjects in each group underwent breath H2 excretion measurement after ingestion of 250 ml of a sugar free, nonabsorbable electrolyte solution and 250 ml of a solution containing lactulose, a nonabsorbable disaccharide. Results After sorbitol ingestion, celiac disease patients showed a significantly higher breath H2 excretion than did healthy volunteers. Otherwise, breath H2 responses to electrolyte solution and lactulose showed no difference between the two groups of subjects. Conclusions In a group of patients with sugar malabsorption, increased breath H2 excretion does reflect malabsorption. The washout or the mixing of the intestinal content or intergroup difference of fermenting activity of the colonic bacteria do not represent interfering factors and do not modify the accuracy of the H2 breath test in day-to-day clinical practice.

Effect of Tegaserod on Recto-Sigmoid Tonic and Phasic Activity in Constipation-Predominant Irritable Bowel Syndrome

OBJECTIVES:In irritable bowel syndrome (IBS), the modulation of neural pathways may be altered and we have recently shown that postprandial recto-sigmoid tone modification is impaired. On pathophysiological grounds, we do not know whether this alteration may have a role in symptom onset and, in particular, whether an effective drug, such as tegaserod, can improve this response together with symptom severity.METHODS:Twenty-two female patients with constipation-predominant IBS (IBS-C), diagnosed according to Rome II criteria, were studied. All subjects underwent an evaluation of the presence and severity of IBS symptoms and the recto-sigmoid barostat test to measure fasting and postprandial recto-sigmoid tone and phasic contractility. They were then randomly assigned to receive either tegaserod 6 mg b.i.d (12 patients) or placebo tablets (10 patients) for 4 wk, according to a double-blind protocol. Symptom assessment and recto-sigmoid tone and contractility were re-evaluated at the end of the treatment.RESULTS:Both symptom severity and postprandial modification of recto-sigmoid tone improved only in the tegaserod group and a significant correlation was evident between the improvement of bloating and the improvement of postprandial recto-sigmoid tone modification. No effect of tegaserod on recto-sigmoid motility index or correlation between motility index and symptom improvement was evident.CONCLUSIONS:In IBS-C female patients, the administration of tegaserod improves symptom severity and is accompanied by an improvement of recto-sigmoid tone response to a meal.

Response to Dr. Mishkin

TO THE EDITOR: The comments of Mishkin et al. suggest that the hydrogen breath test represents a very interesting diagnostic tool, but on the other hand, it is evident once more that its accuracy is still far from perfect. In fact, the recent review of their data (1), in accordance with previous results (2, 3) but not with others, (4, 5) suggests that a possible way of improving the diagnostic accuracy of the hydrogen breath test in the diagnosis of carbohydrate malabsorption may be the combined determination of hydrogen (H2) and methane (CH4) in expired air. Even though all these papers (1–5) are very interesting and draw attention to such a combined breath test, the criteria used to identify a carbohydrate malabsorber on the basis of breath CH4 excretion are always arbitrary, since none of them had been previously validated by comparison with a gold standard, which is not yet available. In our experience, fasting breath CH4 excretion shows a wide range of variability among subjects, and when CH4 values in an individual subject were evaluated it was apparent that the absolute difference between consecutive sampling was proportional to the magnitude of the initial value. Therefore, in contrast to H2 results, it is not possible to identify an absolute increase in breath CH4 concentration as an accurate diagnostic criterion for the diagnosis of carbohydrate malabsorption. It is presumable that the adoption of a percentage increase may be a more valid choice (2). However, commonly used criteria for breath H2 excretion were previously validated by several papers adopting different methodologies (6, 7): for example, Levitt et al. compared breath H2 excretion with ileal recovery of malabsorbed carbohydrate (6), but no measurement of breath CH4 excretion was performed. Newcomer et al. compared breath H2 response to a series of other tests (7), but again no mention of breath CH4 excretion is available. Therefore, Mishkin et al.’s discussion strengthens the concept that the improvement of hydrogen breath test diagnostic accuracy is linked to the improvement of our knowledge about intestinal gas physiology, currently somewhat limited.