Diabetes and
Urinary Tract Infections: The Case Against a Preemptive Strike
Evan David Rosen, M.D., Ph.D.
Assistant Professor of Medicine,
Harvard Medical School
One
of the most frustrating things about diabetes is the myriad
of ways it can hurt you. Regular readers of this Viewpoint know
that patients with diabetes are more prone to heart attacks,
stroke, and peripheral vascular disease, as well as damage to
the eyes, nerves, and kidney. As if this wasn’t enough,
there is another common complication of diabetes that gets less
attention, yet which affects thousands of patients every year.
I’m talking about infections.
Infections can be caused by bacteria, viruses, fungi, or other
pathogens, and patients with diabetes are more prone to a whole
slew of them. Some of these infections are rare and potentially
lethal, like mucormycosis, which almost never affects people
without diabetes. Others are more common, like athlete’s
foot, pneumonia, and urinary tract infections. While anyone
can come down with these conditions, folks with diabetes are
more likely than those with normal blood sugar to be affected.
Furthermore, the complications of those infections can be much
more severe in people with diabetes, and can be more difficult
to treat.
Take urinary tract infections,
for example. Women with diabetes are about two to three times
more likely to have bacteria in their bladders than women without
diabetes (interestingly, the same does not appear to be true
for men). There also seems to be an increased risk of the infection
spreading upwards into the kidneys in diabetic patients, and
diabetic women with urinary tract infections are also more likely
to require hospitalization than non-diabetic women.
Why is this the case? Well, diabetes
affects many systems that protect against infection in general,
and against urinary tract infections specifically. Poor circulation
in diabetes reduces the ability of infection-fighting white
blood cells to get where they need to go. When they do get there,
they are less able to ingest the offending bacteria and kill
them than normal white blood cells. Many people with diabetes
also have dysfunctional bladders that contract poorly; this
allows urine to remain in static pools for long periods of time,
providing luxurious ponds for bacteria to grow in.
Because of this propensity for
serious infections of the bladder and kidneys, there is a school
of thought that recommends screening for and treating asymptomatic
bladder infections in diabetic women. Asymptomatic bladder infections
occur when bacteria are found in the bladder by doing a urine
culture, even though the woman has no symptoms and is unaware
of their presence. The logic here is that these bacteria are
likely to be biding their time before causing more serious mischief,
and a pre-emptive strike would benefit patients by preventing
more dangerous infections later.
This idea is not confined to
people with diabetes. At present we look for and treat asymptomatic
bladder infections in pregnant women and in patients about to
have surgery on their bladders or kidneys. On the other hand,
there are studies showing that this “screen and treat”
approach does no measurable good in other groups of patients
prone to urinary tract infections, such as those with spinal
cord injuries, or elderly folks in nursing homes.
A new study now shows that the
“screen and treat” strategy is not worthwhile in
women with diabetes. Researchers in Canada took a little over
a hundred women with diabetes (80% had type 2 diabetes) who
had two positive urine cultures but no symptoms of a urinary
tract infection. They split the women into two groups, one that
received standard antibiotic therapy, while the other got a
placebo. Not surprisingly, taking the antibiotic was found to
clear the urine of bacteria in the majority of women. Over the
next two years, however, both groups had the same rates of symptomatic
urinary tract infection and hospitalization. Antibiotic therapy
was unable even to delay the onset of the next episode of symptomatic
urinary tract infection.
Screening and treating hundreds
of thousand of diabetic women each year for asymptomatic bladder
infections would cost an awful lot of money, and this new study
makes it clear that it’s not worth the expense. Furthermore,
given the rise of drug-resistant strains of bacteria, there
is even more incentive to cut back on unnecessary antibiotic
prescriptions. On the down side, women with diabetes will continue
to be at increased risk of serious urinary tract infection relative
to non-diabetic women, and we find ourselves no closer to closing
the gap.
Reference:
Harding, Godfrey K.M., Zhanel,
George G., Nicolle, Lindsay E., Cheang, Mary, the Manitoba Diabetes
Urinary Tract Infection Study Group, Antimicrobial Treatment
in Diabetic Women with Asymptomatic Bacteriuria. New England
Journal of Medicine 2002 347: 1576-1583
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