Bariatric Surgery Halts Subclinical Kidney Deterioration

http://www.medscape.com/viewarticle/766296?src=nl_topic

June 25, 2012 (San Diego, California) — Obese individuals who undergo bariatric surgery show improved renal function 1 year later, even if their renal function was within normal range at baseline.

The findings, presented here at the American Society for Metabolic and Bariatric Surgery (ASMBS) 29th Annual Meeting, suggest that addressing obesity early can protect against the first subclinical steps toward chronic kidney disease (CKD), said Wei-Jei Lee, MD, PhD, from Min-Sheng General Hospital and National Taiwan University Hospital.

"With bariatric surgery, we are attacking the 2 main culprits of chronic kidney disease: high blood sugar and high blood pressure," Dr. Lee said in a statement from the meeting. "However, this study suggests the earlier we treat CKD in the disease process with bariatric surgery, the more favorable the impact on the kidney."

The study included 233 obese individuals with a mean age of 33 years and a mean body mass index (BMI) of 39.5 kg/m2. More than 90% of the participants had type 2 diabetes, and nearly half had hypertension.

At baseline, more than half of the cohort (54.8%) had normal kidney function, defined as an estimated glomerular filtration rate (eGFR) of 90 to 125 mL/minute; 26.2% of the patients had hyperfiltration, defined as more than 125 mL/minute; and the remainder had either stage 2 CKD (16.7%) or stage 3 CKD (2.6%), defined as an eGFR of 60 to 90 mL/minute and an eGFR of 30 to 60 mL/minute, respectively.

"The only difference between the groups was age, with the patients with kidney disease being about 6 years older," said Dr. Lee. "There was no difference in sex, blood pressure, glucose, or duration of diabetes. That means obesity itself is a risk factor, and aging is a key factor."

Most of the patients (82%) underwent a gastric bypass procedure, with the remaining undergoing gastric restrictive surgery.

One year after surgery, weight loss (28% - 30%) and BMI (26 - 28 kg/m2) were similar, regardless of baseline kidney function.

Among patients with impaired kidney function at baseline, GFR went from 49.5 to 66.8 mL/minute in the CKD 3 group, from 76.8 to 93.3 mL/minute in the CKD2 group, and from 146 to 133 mL/minute in the hyperfiltration group.

However, "most interesting was the normal GFR group," said Dr. Lee, in which an improvement was seen from 105.7 mL/minute presurgery to 114.2 mL/minute postsurgery. "So even in the normal group, there was already some deterioration."

Blood pressure and serum creatinine improved for all patients, he said.

Among a subgroup of 84 patients for whom pre- and postsurgical urine Protein measurements were available, the percentage of patients with normal levels increased from 34.5% presurgery to 59.5% postsurgery. Similarly, although 39.3% of patients had moderate microalbuminuria (30 - 300 mg/L) before surgery, this dropped to 22.6% after surgery. Finally, although 26.2% of patients had severe microalbuminuria (>300 mg/L) before surgery, only 17.8% had it after.

As a result of the surgery, virtually no patients remained at CKD stage 3, and most patients with CKD stage 2 reverted to normal kidney function, said Dr. Lee.

The study shows that renal dysfunction occurs often with obesity and may be intercepted in its early stages with bariatric surgery, he said.

He added that increased intraabdominal pressure and renal sinus fat most likely contribute to impaired renal function.

Carel le Roux, MB ChB, head of the clinical obesity program at Imperial Weight Center, Imperial College, London, United Kingdom, has recently published a study showing that bariatric surgery improves renal function in obese patients with preexisting renal impairment. The study also showed a reduction in renal and systemic inflammation.

Reached for comment by Medscape Medical News, Dr. le Roux noted that "clinicians should be very cautious to interpret the reduction in creatinine (and any calculations based on creatinine such as eGFR) as improvement in renal function, because after bariatric surgery, lean body mass reduces. It is the reduction in lean body mass that is responsible for the changes in creatinine and eGFR, and not renal function improvements per se."

He added, "better markers should be used, such as Cystatin C or even chromium EDTA clearance tests, before a patient is wrongly told their renal function has improved. Moreover, changes in the urine albumin/creatinine ratio [are] also very prone to misinterpretation. Two samples should be analyzed prior to surgery, as well as after surgery, to compensate for the variation that may naturally occur."

"Having said that, the pleiotropic effects of bariatric surgery with improved glycemia, blood pressure, and inflammation may well be responsible for improved renal function, but we should remain cautious until better evidence becomes available," Dr. le Roux cautioned.

Dr. Lee disclosed financial arrangements with Covidien, J&J, and Allergan. Dr. le Roux has disclosed no relevant financial relationships.

American Society for Metabolic and Bariatric Surgery (ASMBS) 29th Annual Meeting: Abstract PL 108. Presented June 20, 2012.

Woohoo! More reason to drink the KoolAid.

I don't have any kidney issues that I know of... but, that's awesome for everyone who it applies to!!!

I am in stage 3 kidney disease. I am so glad to read what you wrote. When I had my blood work done, the nephrologist said my protein was fine, but my calcium was up a little and suggested I give up the yogurt for a while. I have lactose intolerance ( so, no real milk products ). So, I gave up the yogurt and only taking calcium supplements, and the test was fine this time.