Gastric reduction surgery can significantly increase patient's risk of developing allergy

Amongst other things, operations to reduce the size of the stomach can significantly increase the patient's risk of developing an allergy. This is the conclusion of a study conducted by the Medical University of Vienna. The study was set up jointly between the University Department of Surgery, headed up by Gerhard Prager, and the Institute of Pathophysiology and Allergy Research at MedUni Vienna. With a large part of the stomach removed, bits of food pass almost "unchanged" into the intestine, because the stomach is no longer able to produce enough digestive juices. This increases the risk of allergies developing in the gut. Study author, Eva Untersmayr-Elsenhuber, stresses this point on the occasion the upcoming World Bowel Day on 7 November.

The study was conducted in connection with endoscopic gastric reduction operations on severely obese patients. "The surgery is performed from a body mass index of 35 kg/m² where there are other existing disorders and from a BMI of 40 kg/m² where there are no such comorbidities.  And, depending on the preliminary findings - the preparation period is between 4 and 6 months - and confirmation of suitability for surgery, the operation is performed," explains Untersmayr-Elsenhuber.

The stomach of an extremely obese person is not usually much larger than that of a person of normal weight and has a capacity of around 1.2 - 1.6 litres. "However, there is a significant difference in subsequent expansion and hence satiety - they need to and are able to eat more," says the immunologist, who has dedicated herself to studying the risk factors for the onset of allergies and to developing new treatments.

Following gastric reduction surgery, the stomach only has a residual volume of 15 - 25 ml. The operation results in a huge improvement in the quality of life for the patient, who is then able to lose a lot of body weight within a short period of time. However, the "residual stomach" is no longer able to produce sufficient digestive juices and hence to break food down into its respective components, which now pass "unchanged" into the intestine. Since the intestine is regarded as the place where allergies develop, this therefore increases the patient's risk of allergic reactions.

In most cases patients are able to leave hospital 2 or 3 days after the procedure but, for the reasons given above, their post-operative treatment is costly. A total of 34 different allergens were tested in the context of the study. Otherwise, regular routine checks are carried out every 3 months for vitamins, folic acid, all hormones including thyroid levels and iron. After one year these checks revert to an annual frequency - for the entire lifetime of the patient. "However, in future the allergy risk should also be considered and the patients monitored accordingly," says Untersmayr-Elsenhuber.

In a brochure jointly produced with the inter-university Messerli Research Institute Vienna (together with VetMedUni Vienna), MedUni Vienna stresses the importance of correct nutrition and hence also of the gastrointestinal tract in preventing allergies. In addition to the generally accepted No-Nos such as smoking and drinking alcohol during pregnancy, the recommended advice for preventing allergies includes exclusively breastfeeding babies up to the age of 4 months, avoiding low-allergen diets (except in the case of existing allergies), avoiding cesarean sections and the use of antibiotics (except where medically necessary).