1. Endoscopy Unit, The Second University Clinic, I. M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
2. Department of Pathology, I. M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
3. Department of Internal Diseases Propedeutics, Gastroenterology and Hepatology, I. M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia