Regression of Renal Dysfunction in Long Term Follow-up After Roux-en-Y Gastric Bypass

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.