Mingwei Ni, MD, PhD1, John Lieske, MD2, Todd Kellogg, MD2. 1Kaiser Permanente South Baltimore County Medical Center, 2Mayo Clinic
Laparoscopic Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) are the most commonly performed bariatric procedures. Hyperoxaluria is common after RYGB and is associated with increased incidence of calcium oxalate kidney stones. However, the effect of SG on nephrolithiasis risk is less clear. The potential impact of bariatric surgery on renal function remains unclear. Therefore, we conducted a retrospective study to evaluate changes in urine oxalate excretion and renal function in a cohort of patients in the first year after Roux-en-Y gastric bypass versus sleeve gastrectomy. Patients undergoing RYGB or SG at Mayo Clinic were identified between 2000 and 2013. Pre- and post-operative urinary oxalate levels were available in a total of 18 RYGB and 7 SG patients. Estimated glomerular filtration rate (eGFR) was determined using the CKD EPI creatinine equation. Pre and postoperative serum Creatinine (Cr) data were available for 260 RYGB and 107 SG patients. These patients were further stratified into groups of normal preoperative renal function and chronic renal insufficiency based on eGFR, and the effects of RYGB versus SG on the renal function were further evaluated. By one year after surgery, the %EWL is 69.2±1.3% in RYGB and 59.5±4.9% in SG, respectively. Postoperative urine oxalate excretion was measured at 6 months and 12 months after index surgery. In RYGB patients, it was 0.34±0.16 mmol/L (6 months) and 0.56±0.23 mmol/L (12 months). In SG patients, it was 0.24±0.07 mmol/L (6 months) and 0.28±0.13 mmol/L (12 months). Urine oxalate excretion increased significantly 1 year after RYGB (p<0.01), but did not change after SG. Postoperative Cr decreased significantly 6 months and 12 months after RYGB (p<0.01), but remained unchanged after SG. In terms of postoperative eGFR, there was no significant change in normal renal function patients after either bariatric procedure. However, it increased significantly after lap RYGB (p<0.001) in chronic renal insufficiency patients. The change in eGFR was not observed chronic renal insufficiency patients after SG. Our results suggest urine oxalate excretion increases after RYGB but not SG. In renal insufficient patients, serum Cr falls after RYGB but not SG. Similarly, eGFR increased significantly after RYGB but not SG in these patients. There was no change in either Cr or eGFR in normal renal function patient underwent bariatric surgery. Furthermore, the changes in serum Cr and eGFR were not associated with %EWL after surgery. Longer term follow up will be needed to determine if these effects persist over time.
Presented at the SAGES 2017 Annual Meeting in Houston, TX.
Abstract ID: 77286
Program Number: P570
Presentation Session: Poster (Non CME)
Presentation Type: Poster
