Dr. Tollens is recognized as one of the leading international experts of complex hernia surgeries and is an active member of the European and Asian Hernia Surgery Society. He frequently makes contributions to national and international congresses in minimally Invasive surgery and Herniology. he runs annually more than 25 international courses on hernia surgery. He also participates in clinical trials and has published several clinical papers in different international research journals. Dr. Tollens has given more than 400 international communications on different congresses worldwide and published more than 50 international peer reviewed articles. Moreover, he has travelled extensively over the world and in the Middle East covering annually the UAE, Qatar, Bahrain, Oman, Saudi, Kuwait, Egypt.