Urinary Tract Infection - Risk Factors

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Click the icon to see an image of vesicoureteral reflux.

Risk Factors in Men

Men become more susceptible to UTIs after 50 years of age, when they begin to develop prostate problems. From 5 - 15% of men over 65 will have asymptomatic bacteriuria. Benign prostatic hyperplasia can produce obstruction in the urinary tract and increase the risk for infection. In men, recurrent urinary tract infections are associated with prostatitis, an infection of the prostate gland that can also be caused by E. coli. [For more information, see In-Depth Report #71: Benign prostatic hyperplasia.]

Institutionalization

Hospitalizations and Catheters. About 40% of all infections that develop in hospitalized patients are in the urinary tract. The organisms that cause infections in hospitals (called nosocomial infections) are usually different from those that commonly cause UTIs. They are also more likely to be resistant to standard antibiotics. Hospitalized patients at highest risk for such infections are those with in-dwelling urinary catheters, patients undergoing urinary procedures, long-stay elderly men, and patients with severe medical conditions.

About 80% of UTIs in the hospital are due to catheters. Nearly all patients who need urinary catheters develop high levels of bacteria in their urine, and the longer the catheter is in place, the higher the risk for infection. Catheterized patients who develop diarrhea are nine times more likely to develop UTIs than are patients without diarrhea. In most cases of catheter-induced UTIs, the infection produces no symptoms. Because of the risk for wider infection, however, anyone requiring a catheter should be screened for infection. Catheters should be used only when necessary and should be removed as soon as possible.

Nursing Homes. All older adults who are immobilized, catheterized, or dehydrated are at increased risk for UTIs. Nursing home residents, particularly those who are incontinent and demented, are at very high risk. Up to 40% of elderly patients who live in nursing homes will contract a urinary tract infection.

Anatomical Abnormalities in Adults

Some people have structural abnormalities of the urinary tract that cause urine to stagnate or flow backward into the upper urinary tract. Such conditions include:

• A prolapsed bladder (cystocele) can result in incomplete urination so that urine collects, creating a breeding ground for bacteria.
• Tiny pockets called diverticula sometimes develop inside the urethral wall and can collect urine and debris, further increasing the risk for infection.

Click the icon to see an image of a cystocele.

Antibiotics as Risk Factors for UTIs

Antibiotics often eliminate lactobacilli, the protective bacteria, along with harmful bacteria. This causes an overgrowth of E. coli in the vagina. In one study, the risk for UTI increased during the 15 to 28 days that women were taking antibiotics. In fact, some research suggests that taking antibiotics for a urinary tract infection increases the risk for a subsequent infection.

Medical Conditions That Increase the Risk for UTIs

Diabetes. Diabetes puts women at significantly higher risk for asymptomatic bacteriuria. The longer a woman has diabetes, the higher the risk. (Control of blood sugar has no effect on this condition.) The risk for UTI complications is also higher in people with diabetes. In fact, certain UTI-related abscesses are reported only in patients with diabetes. These patients are also at higher risk for fungal-related UTIs.

Kidney Problems. Nearly any kidney disorder increases the risk for complicated UTIs.

AIDS and Immunosuppressed Patients. Any infection is dangerous in people whose immune systems are damaged, and UTIs are no exception, particularly pyelonephritis.

Sickle-Cell Anemia. Patients with sickle-cell anemia are particularly susceptible to kidney damage from their disease, and UTIs put them at even greater risk.

Kidney Stones. In some cases, kidney stones can cause urinary tract obstruction that leads to infection, particularly pyelonephritis. Symptoms of severe urinary tract infection in people with a history of kidney stones may indicate obstruction, which is a serious condition.

Click the icon to see an image of kidney stones.

Review Date: 06/16/2006
Reviewed By: Harvey Simon, M.D., Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital