Enteric hyperoxaluria, nephrolithiasis, and oxalate nephropathy:
potentially serious and unappreciated complications of Roux-en-Y
Wayne K. Nelson, B.A.
, Scott G. Houghton, M.D.
, Dawn S. Milliner, M.D.
John C. Lieske, M.D.
, Michael G. Sarr, M.D.
Mayo Medical School, Mayo Clinic College of Medicine, Rochester, Minnesota
Department of Surgery, Mayo Clinic College of Medicine, Rochester, Minnesota
Division of Nephrology, Mayo Clinic College of Medicine, Rochester, Minnesota
Received May 13, 2005; revised June 27, 2005; accepted July 7, 2005
Abstract Background: Neither the presence nor prevalence of enteric hyperoxaluria has been recognized
after Roux-en-Y gastric bypass (RYGBP). We have noted a high rate of oxalate nephrolithiasis and
even 2 patients with oxalate nephropathy in this patient population postoperatively. Our aim was to
determine the frequency of the occurrence and effects of enteric hyperoxaluria after RYGBP.
Methods: Retrospective review of all patients at our institution diagnosed with calcium oxalate
nephrolithiasis or oxalate nephropathy after standard (n ϭ 14) or distal (n ϭ 9) RYGBP. The mean
postoperative follow-up was 55 months.
Results: A total of 23 patients (14 men and 9 women; mean age 45 years; mean preoperative body mass
index 55 kg/m
) developed enteric hyperoxaluria after RYGBP, deﬁned by the presence of oxalate
nephropathy (n ϭ 2) or calcium oxalate nephrolithiasis (n ϭ 21) and increased 24-hour excretion of
urinary oxalate and/or calcium oxalate supersaturation. Enteric hyperoxaluria was recognized after a
mean weight loss of 46 kg at 29 months (range 2–85) after RYGBP. Two patients developed renal failure
and required chronic hemodialysis. Of the 21 patients with nephrolithiasis, 14 had no history of nephroli-
thiasis preoperatively, and 19 of 21 required lithotripsy or other intervention. Of the 23 patients, 20 tested had
increased oxalate excretion, and 14 of 15 tested had high urine calcium oxalate supersaturation.
Conclusion: Enteric hyperoxaluria, nephrolithiasis, and oxalate nephropathy must be considered
with the other risks of RYGBP. Efforts should be made to identify factors that predispose patients
to developing hyperoxaluria. © 2005 American Society for Bariatric Surgery. All rights reserved.
Keywords: Nephrolithiasis; Gastric bypass; Bariatric surgery; Hyperoxaluria; Kidney failure
Roux-en-Y gastric bypass (RYGBP) has proved to be
a more effective method of both short- and long-term
weight loss than diet alone for patients with morbid
obesity . Unlike jejunoileal bypass, RYGBP has never
been reported to be associated with enteric hyperoxaluria
or the sequelae of oxalate nephrolithiasis and oxalate
nephropathy. However, we have noted a seemingly high
rate of these complications in patients having undergone
RYGBP at our institution and elsewhere. The aim of this
study was to review the frequency of occurrence of en-
teric hyperoxaluria after RYGBP.
After approval by our institutional review board on Oc-
tober 14, 2004, all Mayo Clinic Rochester patients diag-
nosed since 1985 with nephrolithiasis, oxalate nephropathy,
Presented at the plenary session of the 22nd Annual Meeting of the
American Society for Bariatric Surgery, Orlando, Florida, June 29, 2005.
Winner of the John Halverson award for Best Resident paper.
*Reprint requests: Michael G. Sarr, M.D., Gastroenterology Research
Unit (AL 2-435), Mayo Clinic College of Medicine, 200 First Street
Southwest, Rochester, MN 55905.
Surgery for Obesity and Related Diseases 1 (2005) 481– 485
1550-7289/05/$ – see front matter © 2005 American Society for Bariatric Surgery. All rights reserved.