Department of Gastroenterology, Xijing Hospital, the First Affiliated Hospital of Air Force Medical University, Xi'an, China.

Correspondence: Ting Duan, BM, Department of Gastroenterology, Xijing Hospital, the First Affiliated Hospital of Air Force Medical University, Changle W Rd, Xincheng District, Xi'an 710032, China ([email protected]).

The authors report no declarations of interest.