UroToday.com – “Those who cannot remember the past are condemned to repeat it.” (George Santayana in The Life of Reason 1905). One of the first unintentional human models created for calcium oxalate stone formation was in the obese patient who underwent a jejunal ileal bypass.

In this patient population, the risk of stone disease at 5 years after surgery rose to approximately 20%. In some patients, renal failure resulted. Given this situation, in 1979, the Food and Drug Administration declared a moratorium on jejunal ileal bypass.

Fast-forward 30 years. Enter the Roux-en-Y gastric bypass surgery for obesity. In this comparison of 4,639 patients undergoing this procedure vs. 4,639 nonoperated obese patients, the incidence of urolithiasis (stones in kidney, bladder and/or urethra) was 7.65% vs. 4.63% (p < 0.001) with all patients having a minimum of 3 years of follow-up over the period from 2002-2006. Of note, Asplin and Coe had previously noted in patients undergoing the Roux-en-Y gastric bypass, that oxalate levels averaged 78.4 mg., more than double normal oxalate levels. Indeed, the calcium oxalate super saturation among these patients was similar to what was seen in the jejunal ileal bypass patients 30 years ago. To be sure, these patients are at an increased risk of stone formation after their procedures. Appropriate dietary measures were recommended by the authors (increased fluid intake, low protein diet, low salt diet, normal calcium diet); however, recommending a diet to someone who has undergone an operative procedure for obesity seems futile at best. Are we rediscovering what we already knew and have we now sewn seeds that over time will lead to worsening urolithiasis and new cases of renal failure? Caveat emptor.

Matlaga BR, Shore AD, Magnuson T, Clark JM, Johns R, Makary MA
J Urol. 2009 Jun;181(6):2573-7
doi: 10.1016/j.juro.2009.02.029

Written by UroToday.com Medical Editor Ralph V. Clayman, MD

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