Obesity by itself, independently from its associated comorbidities, is detrimental to the kidney function. The objective of this is study is to describe the improvement of the glomerular filtration rate (GFR) in chronic kidney disease patients when compared to a population with normal kidney function, after Laparoscopic sleeve gastrectomy (LSG).
A retrospective chart review of all patients who underwent LSG at our institution for the last 6 years was conducted. Kidney function was assessed using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and classification pre-operatively and at 12 months follow-up. Propensity score matching (1:1 ratio) was used to match kidney disease patients to normal GFR patients. All analyses were performed on a complete-case basis. All tests were two-tailed and performed at a significant level of 0.05. Statistical software R, version 3.3.1(2016-06-21) was used for all analyses.
Of the 1330 bariatric patients who underwent LSG, 18.79% (n=250) met the criteria for CKD-EPI GFR calculation. 42% (n=105) of patients were classified as Chronic kidney disease (CKD) stage ≥2. After matching 50% (n=38) of males, 50% (n=67) females, 50.54% (n=93) whites and 46.15% (n=12) non-whites were CKD stage ≥2. GFR difference was 8.26 ±11.89 mL/min/1,73m2 in CKD stage ≥2 as compared to -1.98 ±10.25 mL/min/1,73m2 in normal population (p=<0.001) at 12 months follow-up. Percentage Estimated Body mass index loss (%EBMIL) was 60.58% ±23.38 in CKD stage ≥2 compared to 80.62% ±53.15 in normal population (p=<0.001)at 12 months follow-up. Table 1 describes these findings. For the relationship between weight loss (%EBMIL) and the preoperative-GFR, the result of simple linear regression model reveals that preoperative-GFR is significantly associated with %EBMIL. The estimated coefficient is 0.378 (P=0.003), which means with 1 unit increase of preoperative-GFR, the %EBMIL increase 0.378. For the relationship between weight loss and the changes in renal function, the results of simple linear regression model reveal that the difference in BMI was not significantly associated with GFR difference (P=0.385).
There is a clear improvement of the GFR in morbidly obese patients with CKD following LSG, improvement is significant in patients with CKD stage ≥2 and is not related to weight loss. Preoperative-GRF has a positive direct proportional impact in %EBMIL. Prospective studies are needed to further understand these findings.