Does Obesity Kill Kidneys?

Kidneys are exquisitely sensitive to many risk factors that can also accelerate atherosclerosis and heart disease. Thus, high blood pressure and diabetes are well-established risk factors for chronic kidney disease (CKD).

Because both hypertension and diabetes are in turn linked to obesity, the question is: does obesity increase the risk for CKD?

This questions was now addressed by Meredith Foster and colleagues from the National Heart, Lung, and Blood Institute, Framingham, MA, USA, who studied the relationship between Stage 3 CKD (= moderately reduced kidney function) and BMI in the Framingham Offspring participants (n = 2,676; 52% women; mean age, 43 years) free of stage 3 CKD at baseline who participated in examination cycles 2 (1978-1981) and 7 (1998-2001). (Am J Kidney Dis)

While there was no increased risk of kindey disease in overweight participants, obese individuals had a 68% increased odds of developing Stage 3 CKD (estimated glomerular filtration rate < 59 mL/min/1.73 m(2) for women and < 64 mL/min/1.73 m(2) for men).

However, this relationship became non-significant when data was adjusted for diabetes, systolic blood pressure, hypertension treatment, current smoking status, and high-density lipoprotein cholesterol level.

The authors rightly conclude that the link between obesity and CKD is largely explained by the effect of obesity on other cardiovascular risk factors like hypertension or diabetes.

Clearly, if your excess weight is raising your blood pressure and/or making you diabetic, you may need to start worrying about your kidneys.

AMS
Edmonton, Alberta

Bariatric Nephrology

This morning, I am presenting at the Nephrology Educator's Forum in Lake Louise. The audience are nephrologists from across Canada.

The fact that I was invited to speak on obesity is of course related to the fact that nephrology, as practically all fields of medicine, are beginning to see the impact of the obesity epidemic.

Indeed, from a nephrologist's perspective (remember - I am one), not only is obesity a major driver of the most common causes of end-stage renal failure (i.e. type 2 diabetes and hypertension), it also complicates things for patients on dialysis (especially peritoneal dialysis) and renal transplantation.

While there is an apparent survival paradox, whereby obese patients with end-stage renal failure seem to do better than leaner patients (a similar paradox is seen for other chronic diseases including heart failure and chronic obstructive lung disease), there is a high likelihood that this paradox is largely explained by malnutrition or more severe comorbidities than by a true protective effect of the extra weight. Perhaps, maintaining a higher weight or even gaining more weight is simply a sign of adequate nutrition and therefore a surrogate marker for "better health" and thus better outcomes.

On the other hand, in dialysis patients awaiting transplantation or patients who have had transplants, severe obesity and/or further weight gain can be a major problem. Not surprisingly, there is now an increasing number of reports on patients with end-stage renal failure undergoing bariatric surgery either prior to or following kidney transplantation - apparently with great success.

Clearly, the brunt of the obesity epidemic on nephrology is still ahead - nephrologists, like everyone else, will probably have to brush up on the essentials of bariatric care.

AMS