Nephrology

Reviewing the Literature

9c. RIU0485_07-31.qxd 8/4/10 4:50 PM Page e152 REVIEWING THE LITERATURE News and Views From the Literature Nephrology The Effects of Bariatric Surgery on the Kidneys with 12 subjects (5.97%) in the comparison cohort (P  .0179). One subject in each cohort (0.50%) underwent a surgical procedure for the treatment of an upper urinary tract calculus (P  1.0000). Gastric banding is not associated with an increased risk for kidney stone disease or kidney stone surgery in the postoperative period. Additional long-term studies are required to confirm these findings. Reviewed by Dean G. Assimos, MD Department of Urology, Wake Forest University, Winston-Salem, NC [Rev Urol. 2010;12(2/3):e152-e153 doi: 10.3909/riu0485] © 2010 MedReviews®, LLC Penniston KL, Kaplon DM, Gould JC, Nakada SY The Effect of Gastric Banding on Kidney Stone Disease Semins MJ, Matlaga BR, Shore AD, et al. Urology. 2009;74:746-749. his article evaluated the likelihood of being diagnosed with or treated for an upper urinary tract calculus after gastric banding. Bariatric surgical procedures are being increasingly used in the treatment of patients with morbid obesity. Certain malabsorptive bariatric procedures have been associated with an increased risk for kidney stone formation. However, the kidney stone risk of gastric banding, a restrictive bariatric procedure, is unknown. A total of 201 patients were identified who underwent gastric banding as well as a control group of 201 obese patients who did not have bariatric surgery. These patients were culled from a national private insurance claims database within a 5-year period from 2002 to 2006. All patients had at least 2 years of continuous claims data follow-up. The 2 primary outcomes were the diagnosis and the surgical treatment of a urinary calculus. After gastric banding, the diagnosis of an upper urinary tract calculus occurred in 3 subjects (1.49%), as compared T e152 VOL. 12 NO. 2/3 2010 Gastric Band Placement for Obesity Is Not Associated With Increased Urinary Risk of Urolithiasis Compared With Bypass REVIEWS IN UROLOGY J Urol. 2009;182:2340-2346. Obesity is associated with multiple health risks. Bariatric surgery is a treatment for clinically severe obesity and is known to increase urolithiasis risk. However, trends in risk over time are not well characterized. Moreover, little attention has been devoted to laparoscopic gastric band placement. A comparison of urinary risk of urolithiasis after the Roux-en-Y and gastric banding procedures was performed. The authors evaluated 24-hour urine collections from 39 subjects (11 men and 28 women; mean age 51 years) after bariatric surgery. Of these subjects, 27 underwent Rouxen-Y gastric bypass and 12 underwent gastric-banding procedures. Mean time since surgery was 3.4 and 2.1 years for the Roux-en-Y gastric bypass and gastric-banding groups, respectively. Urine volume was low in both groups ( 1.5 L daily). Urinary calcium excretion was lower (P  .001) in the Rouxen-Y gastric bypass (100 mg daily) versus the gastricbanding group (191 mg daily). After Roux-en-Y gastric bypass surgery, 48% had a urinary oxalate of 45 mg daily or more compared with 25% after gastric banding. Urinary citrate was less than 370 mg daily for 14 subjects in the Roux-en-Y gastric bypass and for 1 subject in the gastric 9c. RIU0485_07-31.qxd 8/4/10 4:50 PM Page e153 Nephrology banding group. All patients were taking calcium supplements. Dietary intake of high-oxalate foods did not correlate with urinary oxalate excretion or with hyperoxaluria. The study confirmed the risk of urinary stones following the Roux-en-Y gastric bypass procedure as a result of hyperoxaluria, low urine volume, and hypocitraturia. Those with gastric-banding placement had low urine volumes. Future studies should elucidate the effect of nutrition and/or pharmacological therapy on stone risk of both surgeries as their incidence increases. Comments There is an obesity epidemic in the United States involving both adults and children. This problem places such individuals at risk for premature mortality due to complications of a number of associated medical conditions including hypertension, type 2 diabetes mellitus, and coronary artery disease. Obesity has also been identified as a risk factor for nephrolithiasis.1 The results with dietary modifications and pharmacotherapy for weight loss in those with morbid obesity have not been good, and when positive responses occur, they are typically transient. This has prompted many such individuals to undergo bariatric surgery, especially because it can typically be done in a minimally invasive fashion. Studies have demonstrated that bariatric surgery reverses many of the aforementioned medical comorbidities and reduces mortality.2,3 The Roux-en-Y gastric bypass is one of the most frequently performed bariatric operations. The risk of postoperative hyperoxaluria and stone development in individuals undergoing this procedure has been well chronicled.4-7 Patients have also developed renal failure due to oxalate nephropathy after this procedure.8,9 This also occurred in the jejuno-ileal bypass era and was one of the maleffects that led to its abandonment.10 Gastric banding is currently another popular minimally invasive bariatric operation. It is easier to perform and associated with fewer complications. It promotes weight loss but not to the degree achieved with Roux-en-Y gastric bypass. Semins and colleagues reported that patients undergoing gastric banding are not at higher risk for developing kidney stones or needing a stone-removing procedure as compared with a control group of obese patients not undergoing bariatric surgery. However, they previously reported that those undergoing gastric bypass were more at risk for stones and required stone removal more frequently.11 Although these studies were based on information garnered from a national insurance claims database and did not have the rigor of a randomized, prospective trial, these findings and those of others demonstrate that Roux-en-Y gastric bypass is not only a stone risk but may be detrimental to overall renal health. Furthermore, those with morbid obesity have histologic evidence for renal disease, which could be further negatively impacted by profound hyperoxaluria.12 Penniston and associates reported that in a small group of patients those undergoing gastric banding had more favorable postoperative stone risk profiles than those undergoing Roux-en-Y gastric bypass, namely, lower oxalate and higher citrate excretion. More studies are needed to confirm the findings of these 2 groups. In addition, the mechanisms promoting hyperoxaluria in those undergoing Roux-en-Y gastric bypass need to be defined. This should foster the development of a more effective therapy for this problem. Morbidly obese kidney stone formers should be counseled about the risks of increasing stone activity and the potential for developing renal failure after undergoing Roux-en-Y gastric bypass or other malabsorptive bariatric procedures, especially those who are already hyperoxaluric—a condition more common in obese subjects. Perhaps the best procedure for this group may be gastric banding. The urinary metabolic responses in stone formers undergoing bariatric surgery should be monitored closely to avert these risks. In addition, a nonstone former who develops a kidney stone after bariatric surgery should also be carefully evaluated. References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Taylor EN, Stampfer MJ, Curhan GC. Obesity, weight gain, and the risk of kidney stones. JAMA. 2005;293:455-462. Sjöström L, Narbro K, Sjöström CD, et al. Effects of bariatric surgery on mortality in Swedish obese subjects. N Engl J Med. 2007;357:741-752. Longitudinal Assessment of Bariatric Surgery (LABS) Consortium, Flum DR, Belle SH, et al. Perioperative safety in the longitudinal assessment of bariatric surgery. N Engl J Med. 2009;361:445-454. Asplin JR, Coe FL. Hyperoxaluria in kidney stone formers treated with modern bariatric surgery. J Urol. 2007;177:565-569. Duffey BG, Pedro RN, Makhlouf A, et al. Roux-en-Y gastric bypass is associated with early increased risk factors for development of calcium oxalate nephrolithiasis. J Am Coll Surg. 2008;206:1145-1153. Sinha MK, Collazo-Clavall ML, Rule A, et al. Hyperoxaluric nephrolithiasis is a complication of Roux-en-Y gastric bypass surgery. Kidney Int. 2007;72:100-107. Patel BN, Passman CM, Fernandez A, et al. Prevalence of hyperoxaluria after bariatric surgery. J Urol. 2009;181:161-166. Nelson WK, Houghton SG, Milliner DS, et al. Enteric hyperoxaluria, nephrolithiasis, and oxalate nephropathy: potentially serious and unappreciated complications of Roux-en-Y gastric bypass. Surg Obes Relat Dis. 2005;1:481-485. Nasr SH, D’Agati VD, Said SM, et al. Oxalate nephropathy complicating Rouxen-Y gastric bypass: an underrecognized cause of irreversible renal failure. Clin J Am Soc Nephrol. 2008;3:1676-1683. Requarth JA, Burchard KW, Colacchio TA, et al. Long-term morbidity following jejunoileal bypass. The continuing potential need for surgical reversal. Arch Surg. 1995;130:318-325. Matlaga BR, Shore AD, Magnuson T, et al. Effect of gastric bypass surgery on kidney stone disease. J Urol. 2009;181:2573-2577. Serra A, Romero R, Lopez D, et al. Renal injury in the extremely obese patients with normal renal function. Kidney Int. 2008;73:947-955. VOL. 12 NO. 2/3 2010 REVIEWS IN UROLOGY e153