He was deeply interested in the pancreas, commonly referred to as the unknown and mysterious organ, and decided to specialize in pancreatology aiming to advance early detection efforts in pancreatic cancer by ERCP; an emerging modality at that time.

Dr. Shimosegawa’s research covers a wide range of gastroenterology and pancreatology topics, having vigorously studied the pathogenesis and pathophysiology of acute pancreatitis (AP), epidemiology of AP, and developing the criteria for judgment the severity of AP and clinical practice guidelines of AP. He also conducted validation studies on the usefulness of continuous regional arterial infusion (CRAI) of trypsin inhibitor and antibiotics for severe AP and made great advancements towards our knowledge of chronic pancreatitis (CP) by developing clinical diagnostic criteria and practice guidelines for CP. Most notably, he proposed novel diagnostic criteria for early detection CP. Concerning autoimmune pancreatitis (AIP), he played important roles in the classification of AIP into type 1 and 2, and with Dr. Suresh Chari, established the International Consensus Diagnostic Criteria (ICDC) for AIP, which founded a global basis for the clinical practice and research of this disease. In the area of pancreatic cancer (PDAC), he was involved in the formation of practice guidelines for pancreatic cancer in Japan, and studied the molecular mechanism of PDAC, advancing the study of biomarkers as a method for early detection.