Urologic Diseases Research Updates
Spring 2010
No Link between Kidney Stones
and Gastric Banding
According to a study supported
by the National
Institute of Diabetes and
Digestive and Kidney Diseases
(NIDDK), gastric banding—a
surgical procedure that reduces
the size of the stomach—does not
increase the risk of kidney stones.
Gastric banding is one of several
bariatric surgeries used to treat
obesity. These surgeries are
becoming more common due to surgical innovations,
greater availability, and rising obesity
rates. An estimated 30 percent of American adults are
obese with a body mass index (BMI) of 30 or
higher. BMI is a measure of weight in relation
to height. Although initially reserved for people
with extreme obesity—those with a BMI of
40 or higher—bariatric surgery’s effectiveness
in helping people shed pounds, reverse cardiovascular
disease risk factors, and, in some cases,
eliminate type 2 diabetes has caused doctors to
consider it as a therapy for people with milder
obesity.
Bariatric Surgery
The two most common bariatric procedures,
gastric banding and Roux-en-Y gastric bypass
(RYGB), help patients achieve significant weight
loss and are relatively safe in the short term,
according to the NIDDK-funded Longitudinal
Assessment of Bariatric Surgery study. In gastric
banding, the surgeon places an adjustable band
around the top portion of the stomach, thereby
limiting food intake. RYGB limits food intake
by reducing the size of the stomach and diverting
food around the lower portion of
the stomach and part of the small
intestine, reducing the body’s
ability to absorb calories.
The long-term risks of bariatric
surgery are still under investigation.
Studies have shown that
RYGB increases the risk of
kidney stone formation as soon
as 6 months after surgery. Other
studies have found higher urinary
oxalate levels among people who underwent
RYGB or similar gastric bypass procedures, compared
with controls that had no surgery. Along
with limiting the absorption of food, RYGB also limits the absorption of fat, which is shuttled to
the colon where it may facilitate the absorption
of oxalate—a salt cleared by the kidneys and a
major constituent of kidney stones. Michelle J.
Semins, M.D., senior resident in urology at The
Johns Hopkins University School of Medicine,
and colleagues wanted to learn whether a similar
risk was associated with gastric banding.
“As a consequence of the efficacy of bariatric
surgery, the past decade has witnessed a 10-fold
increase in these procedures,” wrote Semins and
colleagues in a report in the August 15, 2009,
online issue of Urology. “Until our present
analysis, though, the effect of gastric banding on
kidney stone disease has never been described.”
Gastric Banding
The researchers compared the prevalence of
kidney stone disease between two similar groups
of obese individuals: one had gastric banding
surgery and the other received no bariatric
surgery. The average age in both groups was
46 years and about 80 percent of participants
were female. Excluded were individuals with
prior kidney disease, including kidney stones.
Whereas previous studies of RYGB patients
showed a higher prevalence of kidney stones compared with controls, the present study
showed the opposite. Two years after gastric
banding, 1.49 percent of participants in the
surgery group had been diagnosed with kidney
stones, compared with 5.97 percent of control
group participants. One participant from each
group underwent a urological procedure to treat
the stones.
The researchers speculated the significantly
lower prevalence of kidney stones in the gastric
banding group may have been a result of weight
loss, as obesity is an independent risk factor for
kidney stone disease. A lower BMI would, presumably,
decrease kidney stone risk.
“In one sense, the present study is a negative one,
in that it failed to demonstrate an increase in the
prevalence of stone disease after gastric banding,”
wrote Semins, et al. “However, in this clinical
situation such negative data are particularly
necessary.” Armed with these data, health care
providers are better suited to help patients—especially those with a history of kidney stone
disease—weigh the risks and benefits of bariatric
surgery.
Semins and colleagues urged larger and longer
follow-up studies to verify their findings. Since
the publication by Semins, et al., a retrospective, epidemiological study supporting their findings
was published by Penniston and colleagues in the
November 2009 issue of The Journal of Urology.
Urology will soon publish a second article about
gastric banding by Semins, et al.
The study was funded by the Hariri Family
Foundation and Mr. and Mrs. Chad and Nissa
Richinson.
The NIDDK has health information about the
complications of obesity, kidney stones, and
bariatric surgery. For more information, visit
www.niddk.nih.gov.
NIH Publication No. 10–5743
April 2010
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