Urinary Tract Infection

The urinary tract includes the kidneys (which filter the blood to produce urine), the ureters (the tubes that carry urine from the kidneys to the bladder), the bladder (which stores urine), and the urethra (the tube that carries urine from the bladder to the outside). Urinary tract infections (UTIs) happen when bacteria get into the urethra and travel up into the bladder.

If the infection stays just in the bladder, it is a called a bladder infection, or “cystitis.” If the infection travels up past the bladder and into the kidneys, it is called a kidney infection, or “pyelonephritis.” Bladder and kidney infections are both types of UTI.

Bladder infections are one of the most common infections, causing symptoms like a burning feeling with urination and the need to urinate frequently. Kidney infections are less common than bladder infections, and can cause similar symptoms, but they can also cause fever, back pain, and nausea or vomiting.

Both bladder and kidney infections are more common in women than men. Most cases of bladder infection in women are uncomplicated and easily treated with a short course of antibiotics. In men, bladder infections may also affect the prostate gland, and a longer course of antibiotics may be needed. Kidney infections can also usually be treated at home with antibiotics, but treatment typically lasts longer. In some cases, kidney infections must be treated in the hospital.

Risk Factors

Urinary tract infections typically occur when bacteria enter the urinary tract through the urethra and begin to multiply in the bladder. Although the urinary system is designed to keep out such microscopic invaders, these defenses sometimes fail. When that happens, bacteria may take hold and grow into a full-blown infection in the urinary tract.

The most common UTIs occur mainly in women and affect the bladder and urethra.

Infection of the bladder (cystitis) — This type of UTI is usually caused by Escherichia coli (E. coli), a type of bacteria commonly found in the gastrointestinal (GI) tract. However, sometimes other bacteria are responsible.

Sexual intercourse may lead to cystitis, but you don’t have to be sexually active to develop it. All women are at risk of cystitis because of their anatomy — specifically, the short distance from the urethra to the anus and the urethral opening to the bladder.

Infection of the urethra (urethritis) — This type of UTI can occur when GI bacteria spread from the anus to the urethra. Also, because the female urethra is close to the vagina, sexually transmitted infections, such as herpes, gonorrhea, chlamydia and mycoplasma, can cause urethritis.

Urinary tract infections are common in women, and many women experience more than one infection during their lifetimes. Risk factors specific to women for UTIs include:

• Female anatomy — A woman has a shorter urethra than a man does, which shortens the distance that bacteria must travel to reach the bladder.
• Sexual activity — Sexually active women tend to have more UTIs than do women who aren’t sexually active. Having a new sexual partner also increases your risk.
• Certain types of birth control — Women who use diaphragms for birth control may be at higher risk, as well as women who use spermicidal agents.
• Menopause — After menopause, a decline in circulating estrogen causes changes in the urinary tract that make you more vulnerable to infection.

Other risk factors for UTIs include:

• Urinary tract abnormalities — Babies born with urinary tract abnormalities that don’t allow urine to leave the body normally or cause urine to back up in the urethra have an increased risk of UTIs.
• Blockages in the urinary tract — Kidney stones or an enlarged prostate can trap urine in the bladder and increase the risk of UTIs.
• A suppressed immune system — Diabetes and other diseases that impair the immune system — the body’s defense against germs — can increase the risk of UTIs.
• Catheter use — People who can’t urinate on their own and use a tube (catheter) to urinate have an increased risk of UTIs. This may include people who are hospitalized, people with neurological problems that make it difficult to control their ability to urinate and people who are paralyzed.
• A recent urinary procedure — Urinary surgery or an exam of your urinary tract that involves medical instruments can both increase your risk of developing a urinary tract infection.

Symptoms

The typical symptoms of a bladder infection include:

• Pain or burning when urinating
• Frequent need to urinate
• An urgent need to urinate
• Blood in the urine
• Discomfort in the lower abdomen

Burning with urination can also occur in women with vaginal infections (such as a yeast infection) or in people with urethritis (inflammation of the urethra). For this reason, it is important to call your health care provider before assuming you have a bladder infection.

Kidney infections can sometimes cause the same symptoms as those of a bladder infection (listed above), but they can also cause:

• Fever (temperature higher than 99.9ºF or 37.7ºC)
• Pain in the flank (one or both sides of the lower back, where the kidneys are located)
• Nausea or vomiting

If you have one or more of the symptoms of a kidney infection, you should see a health care provider as soon as possible. Although most kidney infections do not cause permanent damage, delaying treatment can lead to serious complications.

Evaluation and Diagnosis

Tests and procedures used to diagnose urinary tract infections include:

Analyzing a urine sample — Your doctor may ask for a urine sample for lab analysis to look for white blood cells, red blood cells or bacteria. To avoid potential contamination of the sample, you may be instructed to first wipe your genital area with an antiseptic pad and to collect the urine midstream.

Urine culture — Lab analysis of the urine is sometimes followed by a urine culture. This test tells your doctor what bacteria are causing your infection and which medications will be most effective.

Imaging of the urinary tract — If you are having frequent infections that your doctor thinks may be caused by an abnormality in your urinary tract, you may have an ultrasound, a computerized tomography (CT) scan or magnetic resonance imaging (MRI). Your doctor may also use a contrast dye to highlight structures in your urinary tract.

Cystoscopy — If you have recurrent UTIs, your doctor may perform cystoscopy, using a long, thin tube with a lens (cystoscope) to see inside your urethra and bladder. The cystoscope is inserted in your urethra and passed through to your bladder.

Treatment

Antibiotics usually are the first line of treatment for urinary tract infections. Which drugs are prescribed and for how long depend on your health condition and the type of bacteria found in your urine.

Simple Infection

Drugs commonly recommended for simple UTIs include:

• Trimethoprim/sulfamethoxazole (Bactrim, Septra, others)
• Fosfomycin (Monurol)
• Nitrofurantoin (Macrodantin, Macrobid)
• Cephalexin (Keflex)
• Ceftriaxone

The group of antibiotic medicines known as fluoroquinolones — such as ciprofloxacin (Cipro), levofloxacin (Levaquin) and others — isn’t commonly recommended for simple UTIs, as the risks of these medicines generally outweigh the benefits for treating uncomplicated UTIs. In some cases, such as a complicated UTI or kidney infection, your doctor might prescribe a fluoroquinolone medicine if no other treatment options exist.

Often, symptoms clear up within a few days of treatment. But you may need to continue antibiotics for a week or more. Take the entire course of antibiotics as prescribed.

For an uncomplicated UTI that occurs when you’re otherwise healthy, your doctor may recommend a shorter course of treatment, such as taking an antibiotic for one to three days. But whether this short course of treatment is enough to treat your infection depends on your particular symptoms and medical history.

Your doctor may also prescribe a pain medication (analgesic) that numbs your bladder and urethra to relieve burning while urinating, but pain usually is relieved soon after starting an antibiotic.

Severe Infection

For a severe UTI, you may need treatment with intravenous antibiotics in a hospital.

Complications

When treated promptly and properly, lower urinary tract infections rarely lead to complications. But left untreated, a urinary tract infection can have serious consequences.

Complications of a UTI may include:

• Recurrent infections, especially in women who experience two or more UTIs in a six-month period or four or more within a year.
• Permanent kidney damage from an acute or chronic kidney infection (pyelonephritis) due to an untreated UTI.
• Increased risk in pregnant women of delivering low birth weight or premature infants.
• Sepsis, a potentially life-threatening complication of an infection, especially if the infection works its way up your urinary tract to your kidneys.

Prevention

Women with recurrent UTIs may be advised to take steps to help prevent them, including one or more of the following:

Changes in birth control — Women who develop frequent bladder infections and use spermicides, particularly those who also use a diaphragm, may be encouraged to use an alternate method of birth control.

Over-the-counter products — Taking cranberry juice, cranberry tablets, or a supplement called “D-mannose” has been promoted as one way to help prevent frequent bladder infections. However, several studies demonstrate no benefit with cranberry, and those studies showing that cranberry and D-mannose reduce the risk of recurrent bladder infections are not convincing.

Drinking more fluid — Increasing your fluid intake can help prevent bladder infections.

Urinating after intercourse — Some health care providers recommend this, because it might help flush out germs that could get into the bladder. There is no proof it is effective in preventing bladder infections, but it also is not harmful.

Postmenopausal women — Postmenopausal women who develop recurrent bladder infections may benefit from using vaginal estrogen. Vaginal estrogen is available in a flexible ring that is worn in the vagina for three months (e.g., Estring), a small vaginal insert (Vagifem), or a cream (e.g., Premarin or Estrace). Vaginal estrogen is discussed in more detail in a separate topic review.

Antibiotics — Preventive antibiotics may be recommended if you repeatedly develop bladder infections and have not responded to other preventive measures. Antibiotics are highly effective in preventing recurrent bladder infections but can cause side effects and promote the growth of resistant bacteria, which are more difficult to treat if they cause subsequent UTIs. Therefore, antibiotics for preventing UTIs should only be considered after trying the above preventive approaches. Preventive antibiotics can be taken in several different ways:

• Continuous antibiotics — You can take a low dose of an antibiotic once per day or three times per week for several months to several years.
• Antibiotics following intercourse — In women who develop UTIs after sex, taking a single low-dose antibiotic after intercourse can help to prevent bladder infections. This usually results in less antibiotic use than continuous antibiotics.
• Self-treatment — A plan to begin antibiotics at the first sign of a bladder infection may be recommended in some situations. Before starting this regimen, it is important that you have had testing (urine cultures) at least once in the past to confirm that your symptoms were caused by a bladder infection. This is because it’s possible to have symptoms of a bladder infection but not actually have an infection, in which case antibiotics would not be helpful.