1. The MOH Key Laboratory of Geriatrics, Beijing Hospital, National Center of Gerontology, Beijing, China.
2. The Chinese Academy of Medical Sciences, Beijing, China.
3. Department of Pathology, Beijing Hospital, Ministry of Health, Beijing, China.
4. Department of General Surgery, Beijing Hospital, Ministry of Health, Beijing, China.
5. Department of Ultrasonography, Beijing Hospital, Ministry of Health, Beijing, China.