Chromoendoscopy with particular reference to a modified endoscopic Congo red test

University dissertation from Ervin Tóth, Department of Medicine, Malmö University Hospital, 205 02 Malmö, Sweden

Abstract: Chromoendoscopy, endoscopic tissue staining, is an adjunctive method using chemical agents applied to the mucosal surface in order to aid gastrointestinal endoscopic diagnosis and therapy. Acid producing mucosa in the GI tract may be visualized endoscopically by Congo red staining in combination with stimulation of gastric acid production. Congo red is a reactive indicator dye that changes color from red to dark blue/black at a pH of less than three. We have modified the conventional Congo red test, and characterized a rapid approach, modified endoscopic Congo red test (MCRT). In this test, within five minutes after pentagastrin injection, the Congo red coated normal, acid producing fundal mucosa turns to a blue/black color. The two shortcomings in the original method, the time of dose-response and the dose of acid stimulant pentagastrin, are circumvented by our modification. The dose-response delay was reduced by 63% from 10-20 minutes to around five minutes, and the dose/kg of pentagastrin by 30 times, giving it intravenously instead of intra-muscularly. MCRT was applied in 589 examinations in order to study gastric mucosa in subjects with both non-operated and resected stomachs. MCRT was found to be a rapid, inexpensive and well-tolerated method to visualize acid producing mucosa during routine gastroscopic examination. MCRT increases the diagnostic accuracy of routine gastroscopy in detecting chronic atrophic fundal gastritis (sensitivity from 0.25 to 1.0 and specificity from 0.88 to 0.95, respectively). This is a rapid and accurate method (accuracy 0.98) to detect hypo/achlorhydria during gastroscopic examination. Morphological and functional information provided by MCRT may influence the clinical managements of patients. Future outcome studies should more precisely define the potential indications and the clinical benefit of MCRT.

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