Washington: Gastric bypass surgery can
raise the risk of developing kidney stones, says a new study.
Researchers at Texas University have found
patients who undergo gastric bypass surgery experience changes
in their urine composition that in turn increase their risk of
developing kidney stones, `The Journal of Urology` reported.
The study found that some of these urinary
changes place weight-loss surgery patients at higher risk for
developing kidney stones than obese patients who don`t undergo
the procedure.
For the study, researchers collected urine samples
from 38 study participants. There were 16 women and three men
in each of two groups.
One group had undergone Roux-en-Y gastric bypass
surgery; the second group contained normal obese individuals.
RYGB, which is one of the most commonly performed weight-loss
procedures, involves the creation of a small gastric pouch and
allows food to bypass part of the small intestine.
The researchers found that the excretion of a
material called oxalate in urine was significantly greater in
the participants who had the surgical procedure than those who
did not (47 per cent compared with 10.5 respectively).
In addition, the amount of a chemical citrate in the
urine was low in many gastric bypass patients in comparison to
the obese nonsurgical group (32 per cent to 5 per cent). In
fact, oxalate is found in the majority of kidney stones, while
citrate inhibits stone formation.
"Almost half of the patients who had undergone gastric
bypass and did not have a history of kidney stones showed high
urine oxalate and low urine citrate -- factors that lead to
kidney-stone formation," lead researcher Naim Maalouf said.
The cause for stone formation after bariatric surgery
is not entirely clear, but the study reinforces the message
that weight-loss surgery patients and their physicians should
be alert to the heightened risk, Dr. Maalouf said.
"These findings illustrate that the majority
of patients are at risk for kidney-stone formation after RYGB.
This complication may not be well-recognized in part because
it tends to occur months to years after the bypass surgery,"
Maalouf said.
PTI
