Diagnosis | Fructose intolerance

Diagnosis

The diagnosis of intestinal fructose intolerance or malabsorption is primarily made by means of a breath test. After oral intake of fructose, the exhaled hydrogen is determined at regular intervals. The hydrogen fulfils the function of a marker, which allows a statement about the intestinal metabolism of fructose.If the fasting value of hydrogen increases to more than 20 ppm (parts per million) and complaints in the gastrointestinal tract are indicated at the same time, the probability of a fructose intolerance is high.

A one-week dietary protocol can also substantiate the suspicion. If the hereditary form of fructose intolerance is indicated, small tissue samples are taken from the intestine, liver and kidney. These are then examined for enzyme deficiency.

If the so-called fructose-1-phosphatealdolase is missing, a genetic metabolic disorder is present. Fructosemia is diagnosed by chance in most cases. Those affected notice above all the frequent urination.

Targeted diagnostic tools do not exist. With this form of fructose intolerance, no treatment measures are necessary. A proven method for detecting intestinal fructose intolerance or malabsorption is the H2 breath test.

If the fructose cannot be absorbed in the small intestine, it passes into the large intestine. The bacteria located there process it into hydrogen, carbon dioxide and short-chain fatty acids. The exhaled hydrogen serves as a diagnostic agent.

The increase in value after oral fructose intake allows conclusions to be drawn about the metabolism in the intestine. Adults drink a quarter liter of water in which 25 grams of fructose are dissolved. Children receive a weight-adapted amount of fructose, which corresponds to one gram of fructose per kilogram of body weight.

Before drinking the sugar solution, the fasting value of exhaled hydrogen is first determined. This should ideally be around 0 ppm (parts per million) and is highly dependent on oral hygiene. After fructose intake, the value is determined every 10 and then every 30 minutes.

The measurements cover a total period of about 3 hours. The test is considered positive if, in addition to intestinal complaints (cramps, diarrhea, flatulence), an increase to over 20 ppm from the initial value is measured. An early increase in the hydrogen value may indicate bacterial colonization of the small intestine.