Patients with morbid obesity who also have chronic renal disease (CRD) may improve or stabilize renal function after gastric bypass, according to a study presented here at the American Society for Metabolic & Bariatric Surgery 25th Annual Meeting.
CRD is common in obese patients, and chronic renal failure is more than 7 times higher in patients with body mass index (BMI) of 40 kg/m2 or higher. However, many centers for bariatric surgery will not perform gastric bypass in CRD patients, particularly those receiving dialysis or awaiting kidney transplant.
J. Wesley Alexander, MD, ScD, Center for Surgical Weight Loss, University of Cincinnati College of Medicine, Department of Surgery, and The Christ Hospital, Cincinnati, Ohio, presented the study of CRD patients who had gastric bypass surgery. Of these patients, 10 had gastric bypass after receiving a kidney transplant, 14 had a kidney transplantation later, 17 were receiving dialysis, 8 had "miscellaneous problems with renal disease."
Of the 9 patients who experienced stabilization or improvement of their CRD, 2 were receiving dialysis, and 7 were anticipating a kidney transplant. Two of the 9 patients had been diagnosed with membranous glomerulonephritis, 5 with focal segmental glomerulosclerosis (FSGS), and 2 with diabetes. Their average age at the time of gastric bypass surgery was 43 years. Mean BMI was 48.9 ± 1.9 kg/m2. The surgeries were not complicated by 30-day mortalities, primary deep wound infections, or transfusions.
Medscape General Surgery talked with Dr. Alexander about the association between obesity and renal disease. "Renal function is sometimes altered by inflammatory processes, and obesity is associated with sort of a baseline inflammation, with increased levels of IL-6 and TNF [tumor necrosis factor]. … Those are inflammatory markers, and they get better after a gastric bypass," said Dr. Alexander.
However, he thinks inflammatory processes are a minor part of the picture: "Diabetes is a major part of it because obese patients have a much greater incidence of diabetes than the general population," said Dr. Alexander. "I would say maybe 4 or 5 times as much. In the general population [the occurrence of] diabetes is about 7.9%."
In the present study, 1 case of membranous glomerulonephritis resolved completely after a gastric bypass 8 years ago. Both patients receiving dialysis were able to stop dialysis (for 7 and 27 months, respectively). Renal function of the other patients has been stable for 2 to 5 years since gastric bypass.
The improvement in renal function after gastric bypass surgery can be rapid. "You have major improvement early with a gastric bypass within the first week. About half the patients lose their diabetes within the first week. … It's before weight loss. It's related to hormones in the intestine and in the stomach. It's also related to some hormones in the lower part of the body called incretins. GLP-1 is one of those," explained Dr. Alexander.
Dr. Alexander also mentioned the role of hypertension in renal disease: "Hypertension is a very important potential factor. It's difficult to separate out the roles of these [ie, hypertension and diabetes] in morbid obesity at least. Morbid obese patients have diabetes and have hypertension at a greater rate," he said. "Diabetes is improved, almost always, after gastric bypass. Hypertension is not improved as much as diabetes is, because there are underlying factors, like genetic factors, which play a major role."
The proteinuria and CRD associated with obesity reflect hyperfiltration and increased venous pressure, as well as obesity-related FSGS. Medscape General Surgery discussed the issue of protein intake after gastric bypass surgery with John Dixon, MD, a comoderator of the session, from the Centre for Obesity Research and Education, Monash University, Melbourne, Australia.
"A truly high-protein diet is not necessary after gastric bypass surgery. It needs to be an adequate protein diet, and adequate for that person. Therefore, it's only a theoretical problem that there could be an issue with renal disease," said Dr. Dixon. "Clearly a truly high-protein diet … can exacerbate uremia in renal disease. So we're not concerned that protein is an issue, and it can be adjusted for within that patient's treatment."
Dr. Dixon noted that the type of patients in this study are not as common as the study suggests. "They were covering an unusual group … to get together a really significant number of patients with quite impaired renal function — which is unusual. And therefore, they were able to observe some improvement in some of these and not others." The study showed that patients with FSGS improved with weight loss. "In particular, this is the type of glomerular disease, or kidney disease that is associated with obesity, one we would expect might improve with weight-loss," observed Dr. Dixon.
The authors of the study concluded that, because gastric bypass surgery can improve or stabilize CRD, clinicians should regard CRD as an indication, rather than a contraindication, for gastric bypass surgery in patients with morbid obesity and CRD.
Dr. Alexander has disclosed no relevant financial relationships. Dr. Dixon has disclosed receiving consulting fees from Inamed/Allergan and has ownership interest in Bariatric Advantage.
American Society for Metabolic & Bariatric Surgery 25th Annual Meeting: Abstract PL-26. Presented June 19, 2008.
Pearls for Practice
The association between obesity and renal disease is largely mediated by diabetes, which is likely to improve after gastric bypass surgery. Because gastric bypass surgery can also improve or stabilize CRD, clinicians should regard CRD as an indication, rather than a contraindication, for gastric bypass surgery in patients with morbid obesity and CRD.
Of 49 patients with CRD who underwent gastric bypass surgery, 9 had improvement or stabilization of CRD. Among these 9 patients, 1 of 2 with membranous glomerulonephritis had complete resolution; both patients receiving dialysis were able to stop dialysis; and renal function of the other patients remained stable for 2 to 5 years since their gastric bypass surgery. The surgeries were not complicated by 30-day mortalities, primary deep wound infections, or transfusions.
Reviewed by Ramaz Mitaishvili, MD
