Changes in renal function following Roux-en-Y gastric bypass: a prospective study

Area of Science:

• Nephrology
• Bariatric Surgery
• Metabolic Medicine

Background:

• Mixed results exist regarding the impact of Roux-en-Y gastric bypass (RYGB) on renal function.
• A prospective, repeated-measures controlled study was conducted to clarify this impact.
• The study aimed to identify the optimal method for assessing renal function post-RYGB.

Purpose of the Study:

• To characterize the changes in renal function following RYGB.
• To compare different methods of measuring renal function, including estimated glomerular filtration rate (eGFR) and creatinine clearance (CCL).
• To identify factors correlating with renal function improvement after RYGB.

Main Methods:

• Prospective, repeated-measures controlled study design.
• Collection of clinical data, serum creatinine (SC), and 24-hour urine samples pre- and post-RYGB (6 months).
• Calculation of glomerular filtration rate (GFR) using the Modification of Diet in Renal Disease (MDRD) formula and creatinine clearance (CCL) via 24-hour urine collection (24 CCL) and Cockcroft-Gault (CG) formula.

Main Results:

• RYGB led to a significant decrease in SC (0.83 to 0.72 mg/dl) and improvement in GFR (91.6 to 104.9 ml/min/1.73 m²).
• The CG formula significantly overestimated CCL compared to 24 CCL preoperatively.
• Improvement in 24 CCL correlated with excess weight loss (EWL) and BMI reduction, particularly in hypertensive patients where it also correlated negatively with age.

Conclusions:

• Renal function demonstrably improves after RYGB, with changes in GFR being the most reliable indicator.
• The improvement in 24-hour creatinine clearance (24 CCL) post-RYGB is linked to the patient's weight loss success.
• These findings are especially pronounced in hypertensive patients, highlighting the renal benefits of RYGB in this population.