Jaclyn Chen, MD1, Rouzbeh Mostaedi, MD2, Blythe P Durbin-Johnson3, Mohamed R Ali, MD1, Angelo M De Mattos, MD1, Roger K Low, MD1. 1University of California, Davis Health System, 2Kaiser Permanente Health System, 3University of California, Davis
Morbidly obese patients develop pathologic renal hyperfiltration indicated by higher than normal glomerular filtration rate (GFR). Short term (6-24 months) outcomes after Roux-en-Y gastric bypass (RYGB) have shown either no worsening or decrease in GFR, trending towards normal. We hypothesize that renal hyperfiltration resolves after RYGB with long term (>24 months) stability.
Demographic and comorbidity data were prospectively collected on 1,196 patients who underwent RYGB at a single academic institution from 2002-2012. GFR and serum creatinine (sCr) were examined preoperatively and postoperatively at 2-, 6-, 12-months, and annually up to 10-years. GFR was calculated using the Cockcroft-Gault equation with adjustments for age, gender, and lean body weight. The changes from baseline over time in GFR and sCr were compared between patient subgroups [body mass index (BMI), age, chronic kidney disease (CKD), percentage excess weight loss (%EWL)], using linear mixed effects models. The estimated change from baseline GFR was measured by the geometric mean ratio (time point/baseline).
The majority of the study group were women (n=1046, 87.5%). The mean and median follow-up was 5.1- and 5.0-years, respectively. Women for all BMI categories showed significant decreases from baseline GFR (BMI 30.0-39.9=0.92; BMI 40.0-49.9=0.88; BMI 50.0-59.9=0.84; BMI≥60.0=0.85). In men, GFR did not change significantly for any BMI category; however, sCr showed significant decreases for BMI 40.0-49.9 (0.96) and BMI 50.0-59.9 (0.91). Women for all age groups showed significant decreases from baseline GFR (<40-years=0.86; 40-59-years=0.89; ≥60-years=0.94). In men, there was no significant change from baseline GFR or sCr for the <40- and ≥60-years groups, while there was a GFR increase (1.05, p=0.026) and sCr decrease (0.94, p<0.001) for the 40-59-years group. Women with CKD stage 2 showed no significant change from baseline GFR and decreases from baseline sCr (0.83, p<0.001), and men showed increases from baseline GFR (1.19, p<0.001) and decreases from baseline sCr (0.86, p<0.001). Women with CKD stage ≥3 showed increases from baseline GFR (1.11, p=0.024) and decreases from baseline sCr (0.74, p<0.001). Women with %EWL ≥50% had greater decreases from baseline GFR compared to %EWL <50% (0.89, p<0.001 vs 0.95, p<0.001). Men with %EWL ≥50% showed increases from baseline GFR (1.08, p<0.001) and decreases from baseline sCr (0.94, p=0.001).
Renal hyperfiltration significantly improves in morbidly obese patients who underwent RYGB with long term stabilization of renal function. Patients with CKD stage 2 and ≥3 showed significant regression in renal dysfunction.