Impact of impaired kidney function on cardiovascular risk after bariatric surgery: A matched control study

David Romero Funes, MD, David Gutierrez Blanco, MD, Camila Ortiz Gomez, MD, Emanuele Lo Menzo, MD, PhD, FACS, Rama Ganga, MD, Samuel Szomstein, MD, FACS, Raul J Rosenthal, MD, FACS. Cleveland Clinic Florida

INTRODUCTION: Chronic kidney disease is an important and sometimes underestimated risk factor for cardiovascular disease. Obesity by itself has proven to be detrimental for kidney function and a major factor for cardiovascular disease. Our goal in this study is to establish the impact of impaired kidney disease in the reduction of cardiovascular risk after rapid weight loss following bariatric surgery.

METHODS: We retrospectively reviewed all patients who underwent bariatric surgery from 2012 to 2015. We assessed kidney function using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and cardiovascular risk using Framingham Risk Score (FRS) equation pre-operatively and at 3 and 12 months of follow-up. Our population was divided into two groups: Patients with CKD Stage ≥2 (GFR<90mL/min) and patients with normal GFR. R version 3.3.1 statistical software was used to determine statistical significance.

RESULTS: Of the 1,330 patients reviewed, 22.48% (n=299) met the criteria for CKD-EPI Glomerular filtration rate (GFR) and Framingham Risk Score (FRS) calculations. After matching, 200 patients (15.03%) were left to analyze, 70% (n=140) of which had a Laparoscopic sleeve gastrectomy. Eighty-six patients (43%) had an impaired kidney function (CKD≥2) (Group 1) and 114 patients (57%) had a normal GFR (Group 2). Common demographics and comorbidities after matching are described in table 1. The mean creatinine in Group 1 was 1.25±1.23 mg/dL versus 0.68±0.13mg/dL in Group 2 (P<0001). Glomerular filtration rate was 66.70±20.36mL/min in Group 1 and 101.64±7.82 in Group 2 (P<0001). Patients with CKD≥2 had a significantly greater preoperative cardiovascular risk when compared to normal GFR patients (34.35±23.54% vs 26.58±18.22% respectively P=0.009). At 12 months of follow-up, the Kidney function improved 12.82±19.73mL/min in Group 1 and decreased 5.81±9.79mL/min in Group 2. Furthermore, when the FRS was calculated at 12 months follow-up, patients with impaired kidney function had an absolute risk reduction of 13.05% corresponding to a relative risk reduction(RRR) of 37.3% compared to 9.59% (RRR=36.07%) (P=0.053) in Group 2. The percentage of estimated BMI loss was found to be similar in both groups (69.05±23.86 and 67.06±64.59 respectively P=0.786).

CONCLUSIONS: Bariatric surgery, especially LSG, has a positive impact on kidney function particularly in patients with Chronic Kidney disease stage 2 or greater. Despite these patients having a higher preoperative cardiovascular risk, they showed similar risk reduction when compared to patients with normal kidney function at 12 months of follow-up.