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Bariatric Surgery May Improve Chronic Kidney Disease

Yesterday, I blogged about the fact that obesity may promote the development of kidney disease by making these organs more sensitive to even a moderate increase in blood pressure. Today, I cite an article by Sankar Navaneethan and Hans Yehnert published in the latest issue of the Surgery for Obesity and Related Diseases (SOARD) suggesting that bariatric surgery may halt and perhaps even reverse progressive loss of renal function in severely obese patients with stage 3 chronic kidney disease (glomerular filtration rate [GFR] 30–59 mL/min/1.73 m2). In this retrospective study of 25 patients with average BMI at surgery of around 50 and a mean GFR of 47.9 mL/min/1.73 m2, surgery reduced BMI to 38.4 at the end of 6 months and to 34.5 kg/m2at the end of 12 months. This reduction in body weight was accompanied by a significant reduction in blood pressure and an increase in GFR at 6 months to 56.6 and a further increase at 12 months to to 61.6 mL/min/1.73 m2. These findings are in line with several previous reports of improvement in renal function with weight loss but systematic prospective intervention studies of weight loss in obese patients with impaired renal function are unfortunately still lacking. Nevertheless, it appears that kidney function may well improve with weight loss and that this treatment option should be considered in obese patients presenting with chronic kidney disease. AMS Edmonton, Alberta

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Obesity Makes Kidneys More Vulnerable to Blood Pressure

With all the talk about obesity as a risk factor for diabetes and heart disease, we may often forget that excess weight affects all organ systems. One set of organs that appears particularly sensitive to the ill-effects of excess weight are the kidneys. This is nicely illustrated in a study just published in the American Journal of Kidney Disease by John Munkhaugen and colleagues from the Norwegian University of Science and Technology, Trondheim, Norway. The researchers examined the combined effect of blood pressure (BP) and body weight on the risk for end-stage renal disease or chronic kidney disease (CKD)-related death. Participants included data from 74,986 adults of the first Health Study in Nord-Trøndelag (88% participation rate), which were linked to the Norwegian Renal Registry and Cause of Death Registry. During a median follow-up of 21 years (1,345,882 person-years), 507 men (1.4%) and 319 women (0.8%) initiated renal replacement therapy (n = 157) or died of CKD (n = 669). The risk associated with body weight started to increase from a BMI of 25.0, but this increased risk was not seen in participants with BP less than 120/80 mm Hg. In contrast, in participants with even moderately increased BP (pre-hypertension or hypertension), there was a progressive increase in the risk for kidney disease with increasing BMI suggesting an almost 6-fold increased risk in participants with a BMI greater than 35. The study strongly suggests that individuals with a BMI greater than 30 are increasingly vulnerable to kidney disease even with a modest increase in blood pressure. This finding has several important clinical implications: 1) Blood pressure should be carefully monitored in all individuals with BMI greater than 30. 2) Even moderately elevated blood pressure (pre-hypertension) should be addressed with lifestyle and, if necessary, pharmacological treatment in obese individuals. 3) Blood pressure treatment targets in obese patients may need to be similar to targets in patients with diabetes (i.e. below 130/80 mm Hg). AMS Edmonton, Alberta

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Bariatric Surgery After Kidney Transplants

Although most of my practice today is bariatric medicine, as a trained nephrologist, I continue to keep an eye on the nephrology literature. I was therefore interested to note this recent study on the outcomes and safety of bariatric surgery in patients who underwent kidney transplants. As blogged before, obesity is a significant risk factor for progression of renal failure (not surprising as obesity is a common cause of both hypertension and type 2 diabetes), but obesity also often develops in transplant recipients due to some of the immunosuppressive and other medications that these patients may have to be on. It is therefore not at all surprising that many transplant recipients have (or develop) severe obesity that may warrant consideration for bariatric surgery, which continues to be the only evidence-based treatment for severe obesity. In this paper published in the latest issue of OBESITY SURGERY, Samuel Szomstein and colleagues from the Cleveland Clinic Florida, USA, performed a retrospective chart review of prospectively collected data on five severely obese women (age 30-48; BMI 48-69) after kidney transplantation who underwent laparoscopic bariatric surgery. All patients were females, with a mean age of 40.8 years (range 30-48) and mean body mass index (BMI) of 52.2 (range 48-69). Four patients had laparoscopic Roux-en-Y gastric bypass and one had laparoscopic sleeve gastrectomy. Patient lost an average of 50% of their excess weight at two years post surgery (around the same as in non-transplant patients) and there were no postoperative complications in any patients. Immunosupressive therapy was unaltered after surgery. Although this paper certainly suggests that bariatric surgery can safely be performed in kidney transplant recipients, the rather short two-year follow-up period and the small number of patients certainly does not allow hard conclusions regarding wether or not bariatric surgery will indeed improve life of the transplant and patients. For now, I believe that the decision to perform bariatric patients on recipients of kidney or other transplants will likely remain a case-by-case decision at experienced centres. AMS Vienna, Austria

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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

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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

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