GI Function Test: Intestinal permeability
Biochemistry Overview / Directory
Purpose of the test
Intestinal permeability and absorption tests may be used to differentiate between different categories of gastrointestinal (GI) tract disease and to guide further investigations. Diseases that cause a reduction in the absorptive surface of the gut e.g. coeliac disease, tropical sprue etc, will result in a lower percentage excretion of the monosaccharides. Rhamnose is often the first to fall, as it is dependent on passive absorption through aqueous pores. Lactulose which passes through the tight junctions between cells is unaffected by the above conditions. A reduction in the excretion of all sugars may be seen in severe infective diarrhoea, particularly in HIV infected subjects, due to intestinal hurry resulting in a shorter contact time between the sugars and the gut wall. In the GI tract disease with an inflammatory and ulcerative component (inflammatory bowel disease - IBD) e.g. Crohn’s disease, ulcerative colitis etc, the cell architecture is changed although the total absorptive surface may only be slightly reduced. In these cases lactulose absorption and excretion may be increased with normal results for the monosaccharides, producing a high lactulose-rhamnose ratio (but not due to reduced rhamnose excretion).
Each adult dose contains lactulose 5 grams, rhamnose 1 gram and D-xylose 0.5 gram. This is supplied as concentrated syrup that requires diluting prior to drinking. Test Solution and instructions must be obtained from the Clinical Biochemistry Dept.
(Dietary restrictions: dairy products to be avoided 16hrs prior to test and during the test period). A random baseline urine sample is taken prior to consumption of the sugar solution and then urine is collected for five hours.
Sample Requirements
Universal container for baseline urine sample, urine collection bottle with special preservative (methiolate). Send 25 mL aliquot with record of the 5 hour urine volume
Storage and Transport
First class post within 4 days.
Turnaround Time
1 - 2 Weeks
Price
Price available on application - please contact adrian.turner@kch.nhs.uk. Discounts could be available for significant workloads.
Contacts
Ms Audrey Duffy
T 020 3299 4133
Dr Joanne Marsden
T 020 - 3299 3856
References
Sharpstone D, Neild P, Crane R, Taylor C, Hodgson C, Sherwood R, Gazzard B, Bjarnason I (1999) Small intestinal transit, absorption and permeability in patients with AIDS with and without diarrhoea. Gut 45: 70-6
