Session: Bariatric Surgery and Obesity in CKD and Transplantation (Friday, May 10, 2019)
Presenters: Eric Sheu, Jillian Reece, and Deborah Evans
According to the most recent data from the CDC, one third of the United States is obese. A high proportion of these people are also affected by comorbidities associated with obesity, such as cardiovascular diseases, diabetes, and hypertension, all of which can affect kidney function in important ways.
In an engaging group presentation at the #NKFClinicals, Eric Sheu, Assistant Professor at Harvard Medical School, Jillian Reece, Clinical Bariatric Dietitian at Tufts Medical Center, and Deborah Evans, Manager of Social Work Services at DaVita Kidney Care, discussed diverse perspectives about bariatric surgery and patients with kidney disease.
Obesity is classified using body mass index (BMI) as the main guideline. When the BMI value is 30 or above, the individual is considered obese. However, BMI is an imperfect measurement, because it does not take into account distribution and body composition, which are key aspects in kidney diseases. Still, it is the best parameter that we have.
The impact of obesity on kidney disease can have negative implications both for kidney function and eventual transplantation. “The risk of having complications in kidney transplantation is higher when obesity is present, including increased risk of rejection with higher BMIs,” remarked Eric Sheu. After the transplant, little is known in terms of survival and outcomes in obese patients. There are conflicting studies suggesting either no survival benefit or improved survival after kidney transplant in people whose BMI is above 40.
With the knowledge of how a higher BMI can negatively affect kidney transplantation comes new guidelines. Most hospitals in the United States have now a requirement of a BMI between 30 and 35 to perform the procedure. Unfortunately, only 5% of people in the waiting list for transplant are able to lose enough weight to be eligible for the surgery. Changes in lifestyle have shown little efficacy for people trying to lose weight. Medical therapy can help patients lose twice as much weight as changes in lifestyle, but comes with a significant rebound weight gain when medications are stopped. Bariatric surgery, on the other hand, can lead to much more dramatic weight loss (about 15 points of BMI).
For these reasons, bariatric surgery may be a possibility to help patients achieve the expected BMI while they are waiting for kidney transplant. Retrospective cohort studies involving bariatric surgery and patients with chronic kidney disease (CKD) suggest that the procedure leads to improvement in kidney function and also reduces albuminuria.
There are two main types of bariatric surgery: Roux-en-Y gastric bypass and sleeve gastrectomy. Roux-en-Y gastric bypass is considered the gold-standard procedure and it consists of creating a pouch with a small portion of the stomach, bypassing the proximal portion of the intestine, and rerouting food to be digested at a distal part of the intestine. On the other hand, sleeve gastrectomy consists of removing around 80% of the stomach, leaving a small portion that resembles a banana.
Currently, sleeve gastrectomy has been performed more often due to its simplicity and reduced adverse effects. While both procedures can result in micronutrient deficiency (eg, vitamin D, folate, iron, vitamin B12) and reduced medication absorption, Roux-en-Y gastric bypass has more risks related to kidney stones, intestinal obstructions, and alcohol abuse.
Unfortunately, for patients who have undergone bariatric surgery and have CKD or kidney transplant, there are no best practice guidelines due to lack of good randomized controlled trials. Jillian Reece, the clinical bariatric dietitian on the panel, discussed special considerations for patients with CKD, eg the importance of high biological value proteins in the diet due to higher protein loss and less emphasis on dairy products because of electrolyte abnormalities. She also recommended the use of protein supplements after bariatric surgery, especially the ones formulated for patients with kidney disease.
At the end of the session, Deborah Evans discussed the importance of interdisciplinary teams to support patients who are undergoing procedures or treatments for obesity and kidney diseases. As a social worker, she shared her experience to highlight the importance of understanding the education and cultural background of the patients in order to better support them. For example, when a nutritional guide is provided after a surgical procedure, it is key to assess whether patients know how to prepare a particular food and whether they have access to it. These are fundamental aspects of health literacy that improve the likelihood of success during treatment.
This session illustrated well the complicated interplay of obesity and bariatric surgery in patients with kidney diseases. Safe strategies to reduce the burden of these diseases bring an exciting perspective for current recommendations.
– Post prepared by Andrea Blotta, PhD, AJKD Special Projects Coordinator. Follow her @BlottaAndrea.