Bariatric surgery a silver lining for morbidly obese CKD patients?

Bariatric surgery may provide the key to slowing down disease progression in morbidly obese individuals with chronic kidney disease (CKD), according to data presented at ASN Kidney Week 2019, underpinning the role of weight loss in this setting.

“Obesity is strongly associated with [end-stage kidney disease (ESKD)]. Bariatric surgery … is associated with a decreased risk of ESKD … and may improve access to kidney transplantation for those with severe obesity,” said Dr Alex Chang from the Geisinger Kidney Health Research Institute in Danville, Pennsylvania, US.

The obesity-CKD link

In a large meta-analysis (n=5.5 million) evaluating the link between adiposity measures and mortality, the hazard ratios (HR) for GFR* decline were 1.18, 1.69, and 2.02, respectively, for body mass indices (BMI) 30, 35, and 40 kg/m² vs BMI 25 kg/m². [BMJ 2019;364:k5301] “When you get to a BMI of 35–40 kg/m², regardless of whether you have a GFR of 30 or a normal range, you have a higher risk of ESKD,” explained Chang.

Kidney biopsies of 95 severely obese individuals with normal renal function who will undergo bariatric surgery showed a higher incidence of glomerular abnormalities such as FSGS** (5.3 percent vs 0 percent), globally sclerotic glomeruli (52.6 percent vs 30 percent), increased mesangial matrix (60 percent vs 5 percent), and mesangial cell proliferation (20 percent vs 0 percent) among the severely obese vs healthy controls. [Kidney Int 2008;73:947-955] These imply that patients with relatively normal kidney function are not spared of histopathological changes, noted Chang. “[However,] this is just illustrating the glomerulomegaly in obesity. Whether that is truly pathogenic or not is up for debate.”

In a study comprising overweight/obese individuals with type 2 diabetes (n=5,145), mean 1-year weight loss was higher among recipients of intensive lifestyle intervention (ILI) vs those who received diabetes support/education (8.6 percent vs 0.7 percent). This translated to a 31-percent reduction in the incidence of CKD favouring ILI (HR, 0.69). [Lancet Diabetes Endocrinol 2014;2:801-809] “The challenge lies in getting patients to lose weight,” said Chang, further probing into the role of bariatric surgery in this setting.

A cut in the gut: The pros, cons

Chang presented several studies reflecting the benefits of bariatric surgery. One of which shows five-year outcomes favouring bariatric surgery over intensive medical therapy in terms of improving glycaemic control, lipid profile, weight loss, insulin use, and quality of life. [N Engl J Med 2017;376:641-651] “The striking thing to note [in this study is that] 45 percent of patients who had gastric bypass were no longer on diabetes medications,” said Chang.

In another study on morbidly obese individuals with stage 3–4 CKD (n=1,524), bariatric surgery recipients had higher estimated GFR than those who had no surgery at 3 months (mean adjusted difference, 12.6 mL/min/1.73 m²; p<0.001), which was maintained at 3 years (mean adjusted difference, 9.8 mL/min/1.73 m²; p<0.001). [Am J Kidney Dis 2017;69:380-388]

However, severely obese individuals are often excluded from transplants, as most centres use a BMI exclusion cutoff of 35–40 kg/m². “[Waitlisted] patients with severe obesity … are less likely to get transplanted. There could be other comorbidities at play, too,” said Chang.

A University of Cincinnati study (n=170) showed the potential benefit of bariatric surgery even in the face of transplantation, given the improved kidney transplant candidacy with LSG*** in severely obese individuals. Six out of the 52 LSG recipients were transplanted, with only one postoperative complication reported. [Am J Transplant 2015;15:1360-1368]

Another study comprising 142 ESKD patients showed lower rates of delayed graft function among those who underwent kidney transplant following LSG vs non-LSG transplant recipients (5 percent vs 20 percent; p<0.05). [Am J Transplant 2018;18:410-416] There might be some concern about absorption issues but overall, LSG generated good, if not better, outcomes, noted Chang.

“Although patients with high BMI are at higher risk for complications … there is a benefit for being transplanted vs staying on the list regardless of whatever BMI you start out with,” said Chang.

Taken together, the data supports the potential of bariatric surgery to address CKD issues from a weight loss standpoint.