Small intestinal motility and transit in disease

Critical appraisal of the SIBO hypothesis and breath testing: A clinical practice update endorsed by the European society of neurogastroenterology and motility (ESNM) and the American neurogastroenterology and motility society (ANMS)

BACKGROUND

There is compelling evidence that microbe-host interactions in the intestinal tract underlie many human disorders, including disorders of gut-brain interactions (previously termed functional bowel disorders), such as irritable bowel syndrome (IBS). Small intestinal bacterial overgrowth (SIBO) has been recognized for over a century in patients with predisposing conditions causing intestinal stasis, such as surgical alteration of the small bowel or chronic diseases, including scleroderma and is associated with diarrhea and signs of malabsorption. Over 20 years ago, it was hypothesized that increased numbers of small intestine bacteria might also account for symptoms in the absence of malabsorption in IBS and related disorders. This SIBO-IBS hypothesis stimulated significant research and helped focus the profession's attention on the importance of microbe-host interactions as a potential pathophysiological mechanism in IBS.

PURPOSE

However, after two decades, this hypothesis remains unproven. Moreover, it has led to serious unintended consequences, namely the widespread use of unreliable and unvalidated breath tests as a diagnostic test for SIBO and a resultant injudicious use of antibiotics. In this review, we examine why the SIBO hypothesis remains unproven and, given the unintended consequences, discuss why it is time to reject this hypothesis and its reliance on breath testing. We also examine recent IBS studies of bacterial communities in the GI tract, their composition and functions, and their interactions with the host. While these studies provide important insights to guide future research, they highlight the need for further mechanistic studies of microbe-host interactions in IBS patients before we can understand their possible role in diagnosis and treatment of patient with IBS and related disorders.

Impacts and patterns of disturbed gastrointestinal function in critically ill patients

Disordered upper gastrointestinal tract motility occurs frequently in intensive care unit patients and often represents a substantial treatment challenge. In addition to specific complications such as pulmonary aspiration and diarrhea, abnormal gastrointestinal motility is a limiting factor for delivery and success of enteral nutrition. The pathophysiologies involved are incompletely understood because of the difficulties of making measurements of gastrointestinal function in critically ill patients. With the recent development of techniques that overcome some of these difficulties, the prospects are brighter for significant advances in this field.

Rapid distal small bowel transit associated with sympathetic denervation in type I diabetes mellitus

BACKGROUND

The pattern of progression of a meal from the stomach to the caecum in diabetes mellitus is controversial and the differential roles of transit through the jejunum and the ileum have not been investigated in diabetes.

AIMS

To determine gastric emptying and transit rates through proximal and distal regions of the small bowel in type I diabetic patients.

SUBJECTS

The study included six diabetic patients with evidence of autonomic neuropathy (DM-AN group), 11 diabetics without autonomic dysfunction (DM group), and 15 control volunteers.

METHODS

Gastric emptying and small bowel transit of a liquid meal were evaluated scintigraphically in these subjects. Transit through regions of interest corresponding to the proximal and distal small intestine up to the caecum was determined and correlated with gastric emptying rates, cardiovascular measurements of autonomic function, and the occurrence of diarrhoea.

RESULTS

Gastric emptying and transit through the proximal small bowel were similar in the three groups. The meal arrived to the caecum significantly earlier in DM-AN patients (median; range: 55 min; 22-->180 min) than in the DM group (100 min; 44-->180 min, p < 0.05) or in controls (120 min; 80-->180 min, p < 0.02). Accumulation of chyme in the distal small bowel was decreased in DM-AN patients, who showed values for peak activity (30%; 10-55%) significantly lower than in the DM group (49%; 25-77%, p = 0.02) and controls (50%; 30-81%, p = 0.02). In DM patients (n = 17), the time of meal arrival to the caecum was significantly correlated with both orthostatic hypotension (coefficient of contingency, C = 0.53, p < 0.01) and diarrhoea (C = 0.47, p < 0.05), but not with gastric emptying rates.

CONCLUSIONS

Patients with type I diabetes mellitus and sympathetic denervation have abnormally rapid transit of a liquid meal through the distal small bowel, which may play a part in diarrhoea production.

Abnormal progression of a liquid meal through the stomach and small intestine in patients with Chagas' disease

This study describes the abnormal pattern of gastrointestinal progression of a liquid meal in patients with the digestive form of chronic Chagas' disease. This condition is known as a natural model of intramural denervation of the gut. Sixteen patients with clinical and radiographic evidence of esophageal and/or colonic involvement and 18 healthy volunteers were studied. Orocecal transit time after the ingestion of a 10% lactulose solution (180 ml) tagged with 99mtechnetium was measured by a conventional H2 breath technique. Gastric emptying and the arrival of the front of the meal to regions of interest corresponding to proximal and distal areas of the small intestine were assessed by abdominal scintigraphy. Orocecal transit time was significantly greater (P < 0.05) in Chagas' disease patients (N = 13) than in control subjects (N = 18) (mean +/- SD: 100.7 +/- 48.7 min vs 62.9 +/- 18.2 min). Half-time for gastric emptying of liquids in chagasic patients (N = 9) was significantly lower (P < 0.01) than in controls (N = 7) (9.7 +/- 2.7 min vs 26.4 +/- 3.4 min). The time of arrival of the liquid meal to the proximal small intestine was also significantly shorter (P < 0.02) in patients than in controls (5.6 +/- 3.7 vs 11.4 +/- 5.5 min), but there was no difference between the two groups concerning the time the meal first arrived to the distal small intestine (15.0 +/- 11.0 min vs 23.5 +/- 11.4 min, P > 0.05). These results indicate that patients with Chagas' disease have a combination of exceedingly rapid gastric emptying and abnormally delayed transit of liquids through the more distal segments of the small bowel.(ABSTRACT TRUNCATED AT 250 WORDS)