Z Gastroenterol 2015; 53 - P34
DOI: 10.1055/s-0035-1551722

Carbohydrate malabsorption and carbohydrate-specific small intestinal bacterial overgrowth: diagnostic approach and overlap

D Enko 1, G Kriegshäuser 1, C Kimbacher 1, R Stolba 1, G Halwachs-Baumann 1
  • 1Institute of Laboratory Medicine, General Hospital Steyr, Steyr, Austria

Background: Carbohydrate malabsorption is a considerable problem in patients with non-specific abdominal complaints. While lactose malabsorption is well investigated, few epidemiologic data are available for fructose and sorbitol malabsorption or combined carbohydrate malabsorption syndromes. The purpose of this study was to assess the prevalence rates for primary lactose malabsorption, fructose and sorbitol malabsorption, and carbohydrate-specific small intestinal bacterial overgrowth (cs-SIBO) in an Austrian outpatient center. Additionally the diagnostic value of methane (CH4) measurements in carbohydrate malabsorption breath testing was evaluated.

Methods: In total, 306 adult patients with non-specific gastrointestinal (GI) symptoms underwent genetic testing for LCT (C/T-13910 polymorphism) indicative of primary lactose malabsorption, and a combined hydrogen (H2)/(CH4) breath test for fructose (25 g) and sorbitol (12.5 g) malabsorption. If an H2/CH4 increase > 20 ppm above baseline concentrations was observed within 60 – 120 minutes after sugar ingestion (i.e. colonic passage), patients were classified as malabsorbers. If an early H2/CH4 peak > 20 ppm above baseline concentrations was observed within 60 minutes after sugar ingestion (i.e. small intestinal passage), carbohydrate-specific SIBO (cs-SIBO) was considered.

Results: Seventy-eight (25.49%) patients were C/C-13910 homozygotes, indicating primary lactose malabsorption. Thirty-four (11.11%) and 57 (18.63%) patients were classified as fructose and sorbitol malabsorbers, respectively. Combined states of carbohydrate malabsorption were found in 30 (9.80%) patients. Twenty-nine (9.50%) patients with an early H2/CH4 peak (i.e. within 60 minutes after fructose and/or sorbitol ingestion) were diagnosed with cs-SIBO. Without additional CH4 measurements, only one (0.33%) patient with sorbitol malabsorption, and one (0.33%) with sorbitol-specific SIBO would not have been identified.

Conclusions: Carbohydrate malabsorption is a frequent condition in patients with non-specific GI symptoms. The additional benefit of CH4 breath measurements in the detection of carbohydrate malabsorption is limited. With respect to H2/CH4 breath testing, uniform criteria for the diagnostic workup of these patients are needed.