Need For Better Measure of Kidney Function in Severe Obesity

Dr. John C. Lieske, MD Mayo Clinic, Rochester, MN MedicalResearch.com Interview with
Dr. John C. Lieske, MD
Mayo Clinic, Rochester, MN

Medical Research: What are the main findings of the study?

Dr. Lieske: We followed 11 women before, 6 and 12 months after Roux en Y gastric bypass surgery. The patients successfully lost weight as mean BMI fell from 46 kg/m2 preoperatively to 28 kg/m2 postoperatively. Mean serum creatinine did not significantly change from baseline (0.8 mg/dl) to 12 months (0.7 mg/dl). Hence mean GFR estimated by the CKD-EPI equation (eGFR) did not significantly change from 84 ml/min/1.73 m2 (baseline) to 90 ml/min/1.73 m2 (12 months). However, GFR measured by iothalamate clearance (mGFR) significantly decreased from 108 ml/min/1.73m2 (121 ml/min) to 85 ml/min/1.73 m2 (90 ml/min).


Medical Research: Were any of the findings unexpected?

Dr. Lieske: The change in GFR correlated most strongly with creatinine excretion rather than total body weight. Thus, GFR seems to be particularly influenced by muscle mass.

Medical Research:What should clinicians and patients take away from your report?

Dr. Lieske: GFR falls significantly after gastric bypass surgery, but this change is not detected by serum creatinine or eGFR (which is derived from serum creatinine).

In general, the current eGFR equations are not as accurate in morbidly obese patients (such as our group of patients preoperatively)

Medical Research:What recommendations do you have for future research as a result of this study?

Dr. Lieske:

  • Alternative methods to estimate or measure GFR in morbidly obese patients.
  • At a basic science level, the signals that drive GFR changes with weight loss are currently unknown, and could allow a more complete understanding of renal physiology. These factors could also be relevant for progression of chronic kidney disease

Citation:

Gastric Bypass Surgery and Measured and Estimated GFR in Women

Lieske, John C. et al.
American Journal of Kidney Diseases