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Diabetes and Urinary Tract Infections: The Case Against a Pre-emptive Strike

May 11, 2002

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.


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