Wakamatsu K, et al. – The prevalence of chronic kidney disease (CKD) patients who underwent bariatric surgery in the institution was assessed, and the impact of bariatric surgery on their kidney function as measured by the estimated glomerular filtration rate by Cystatin–C (eGFRcys), was illustrated. Particularly those with pre–CKD (eGFRcys ≥ 60 ml/min/1.73 m2), bariatric surgery resulted in the significant improvement in the eGFRcys values of Japanese patients with morbid obesity. However, the eGFRcys values of CKD patients (< 60 ml/min/1.73 m2) were not ameliorated by surgery.