Prevalence of Chronic Kidney Disease in Morbidly Obese Japanese and the Impact of Bariatric Surgery on Disease Progression.

Background: The prevalence of chronic kidney disease (CKD) among Japanese morbidly obese patients undergoing bariatric surgery and the impact of bariatric surgery on their renal function has not previously been investigated.

Objectives: The aims were to assess the prevalence of CKD patients who underwent bariatric surgery in our institution and to elucidate the impact of bariatric surgery on their kidney function as measured by the estimated glomerular filtration rate by Cystatin-C (eGFRcys).

Setting: The setting of the study was in a single private hospital.

Methods: Two hundred fifty-four consecutive Japanese patients who underwent bariatric surgery were retrospectively analyzed to elucidate the prevalence of CKD. The eGFRcys was calculated to assess the change in the kidney function for 1 year after surgery.

Results: The preoperative prevalence of CKD was as follows: G1, 45.3%; G2, 47.2%; G3, 6.5%; and G4, 0.9%. The eGFRcys values before and after surgery were compared; the G1 and G2 patients showed significantly improved eGFRcys values after surgery (G1 101 [94-108] vs 114 [103-127]; G2 79 [74-84] vs 97 [87-104] ml/min/1.73 m; p < 0.01) with significant weight loss (G1 38.1 ± 6.2 vs 26.5 ± 3.4; G2 38.5 ± 6.9 vs 26.7 ± 3.6 kg/m; p < 0.01). Although the renal function of G3 patients was not improved after surgery (44 [42-47] vs 45 [43-63] ml/min/1.73 m; p = 0.08), successful weight loss was achieved (36.1 ± 6.3 vs 26.6 ± 3.6 kg/m; p < 0.01). In multivariate analysis, postoperative eGFRcys correlated negatively with proteinuria (p < 0.01), age (p < 0.01), and body mass index (p < 0.01) and positively with persistence of antihypertensive drugs.

Conclusion: Bariatric surgery resulted in the significant improvement in the eGFRcys values of Japanese patients with morbid obesity, particularly those with pre-CKD (eGFRcys ≥ 60 ml/min/1.73 m), while the eGFRcys values of CKD patients (< 60 ml/min/1.73 m) were not ameliorated by surgery.