Fructose Malabsorption in Patients With Irritable Bowel Syndrome-like Symptoms: What Is the Role in the Pathogenesis and Clinical Implication?

Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus

OBJECTIVES

Breath tests (BTs) are important for the diagnosis of carbohydrate maldigestion syndromes and small intestinal bacterial overgrowth (SIBO). However, standardization is lacking regarding indications for testing, test methodology and interpretation of results. A consensus meeting of experts was convened to develop guidelines for clinicians and research.

METHODS

Pre-meeting survey questions encompassing five domains; indications, preparation, performance, interpretation of results, and knowledge gaps, were sent to 17 clinician-scientists, and 10 attended a live meeting. Using an evidence-based approach, 28 statements were finalized and voted on anonymously by a working group of specialists.

RESULTS

Consensus was reached on 26 statements encompassing all five domains. Consensus doses for lactulose, glucose, fructose and lactose BT were 10, 75, 25 and 25 g, respectively. Glucose and lactulose BTs remain the least invasive alternatives to diagnose SIBO. BT is useful in the diagnosis of carbohydrate maldigestion, methane-associated constipation, and evaluation of bloating/gas but not in the assessment of oro-cecal transit. A rise in hydrogen of ≥20 p.p.m. by 90 min during glucose or lactulose BT for SIBO was considered positive. Methane levels ≥10 p.p.m. was considered methane-positive. SIBO should be excluded prior to BT for carbohydrate malabsorption to avoid false positives. A rise in hydrogen of ≥20 p.p.m. from baseline during BT was considered positive for maldigestion.

CONCLUSIONS

BT is a useful, inexpensive, simple and safe diagnostic test in the evaluation of common gastroenterology problems. These consensus statements should help to standardize the indications, preparation, performance and interpretation of BT in clinical practice and research.

Fructose Malabsorption in Systemic Sclerosis

The deleterious effect of fructose, which is increasingly incorporated in many beverages, dairy products, and processed foods, has been described; fructose malabsorption has thus been reported in up to 2.4% of healthy subjects, leading to digestive clinical symptoms (eg, pain, distension, diarrhea). Because digestive involvement is frequent in patients with systemic sclerosis (SSc), we hypothesized that fructose malabsorption could be responsible for intestinal manifestations in these patients. The aims of this prospective study were to: determine the prevalence of fructose malabsorption, in SSc; predict which SSc patients are at risk of developing fructose malabsorption; and assess the outcome of digestive symptoms in SSc patients after initiation of standardized low-fructose diet. Eighty consecutive patients with SSc underwent fructose breath test. All SSc patients also completed a questionnaire on digestive symptoms, and a global symptom score (GSS) was calculated. The prevalence of fructose malabsorption was as high as 40% in SSc patients. We also observed a marked correlation between the presence of fructose malabsorption and: higher values of GSS score of digestive symptoms (P = 0.000004); and absence of delayed gastric emptying (P = 0.007). Furthermore, in SSc patients with fructose malabsorption, the median value of GSS score of digestive symptoms was lower after initiation of standardized low-fructose diet (4 before vs. 1 after; P = 0.0009). Our study underscores that fructose malabsorption often occurs in SSc patients. Our findings are thus relevant for clinical practice, highlighting that fructose breath test is a helpful, noninvasive method by: demonstrating fructose intolerance in patients with SSc; and identifying the group of SSc patients with fructose intolerance who may benefit from low-fructose diet. Interestingly, because the present series also shows that low-fructose diet resulted in a marked decrease of gastrointestinal clinical manifestations in SSc patients with fructose malabsorption, our findings underscore that fructose malabsorption may play a significant role in the onset of gastrointestinal symptoms in these patients. Finally, we suggest that fructose malabsorption may be due to reduced fructose absorption by enterocytes, impaired enteric microbiome, and decreased intestinal permeability.