1Department of Internal Medicine, Division of Gastroenterology, Academic Hospital, De Pintelaan 135, B-9000 Ghent
2Department of Internal Medicine, Division of Gastroenterology, Academic Hospital, De Pintelaan 135, B-9000 Ghent; and the Laboratory for Analytical Chemistry, Institute for Nuclear Sciences, Proeftuinstraat 86, B-9000 Ghent [both of the State University of Ghent, Belgium]