This is a powerful noninvasive gastrointestinal test assessment of small intestinal absorption and barrier function in the bowel. It directly measures the ability of two non-metabolized sugar molecules (lactulose and mannitol) to permeate the intestinal mucosa as reflected in the levels of the two sugars recovered in a urine sample collected over 6 hours.

The small intestine uniquely functions as a digestive/absorptive organ for nutrients as well as a powerful immune and mechanical barrier against excessive absorption of bacteria, food antigens, and other macromolecules. Both malabsorption and increased intestinal permeability (“leaky gut”) are associated with chronic gastrointestinal imbalances as well as many systemic disorders.

Increased intestinal permeability of the small intestine can:

• Increase the number of foreign compounds entering the bloodstream
• Allow bacterial antigens capable of cross-reacting with host tissue to enter the bloodstream, leading to auto-immune processes
• Enhance the uptake of toxic compounds that can overwhelm the hepatic detoxification system and lead to an overly sensitized immune system

Hyperpermeability has been observed in a range of disorders such as Inflammatory Bowel Disease (IBD), Irritable bowel syndrome (IBS), food allergy, arthritis, sinusitis, chronic skin conditions. Studies have demonstrated that the increased intestinal permeability observed in patients with ankylosing spondylitis, rheumatoid arthritis, and vasculitis may be an important factor in the development of these disorders.

Decreased permeability, on the other hand, appears as a fundamental cause of malabsorption, subsequent malnutrition, and failure to thrive. In certain disease states of the small intestine, such as gluten-sensitive enteropathy, permeability to large molecules may increase while permeability to small molecules decreases – a result of damage to the microvilli. As a result, nutrients become even less available to assist in the detoxification of antigens flooding the system.