Current status and necessity of new evidences about metabolic surgery from Japan

Metabolic surgery (MS) has already been accepted as the strongest treatment for severely obese patients with some obesity-related diseases (ORDs). The brand-new guideline for MS has been published in this March, and some patients with body mass index (BMI) <35kg/m² have become candidates of MS, especially in type 2 diabetes mellitus (T2DM) patients. Non-alcoholic steatohepatitis (NASH) has become the most important ORD as equal to T2DM because NASH has a risk of liver cirrhosis and carcinogenesis. On the other hand, laparoscopic sleeve gastrectomy (LSG) is the only surgical procedure covered by national health insurance system in Japan; therefore, over LSG occupies over 90 % of MSs and this situation seems to be strange. From these backgrounds, there are some critical problems for us to increase international presence of Japanese bariatric and metabolic surgeons. The one is the shortage of high-impact reports both clinical and basic studies. There is only one high-volume center and others are medium- and low-volume centers; therefore, multi-center studies about T2DM and NASH are warranted led by major domestic societies. Laparoscopic sleeve gastrectomy with duodeno-jejunal bypass (LSG/DJB) for patients with super obesity or T2DM patients with low BMI is also required as primary or revisional procedure. I’ll show the current status of MS for T2DM and NASH in Japan and future perspectives of multi-center studies from Japan.