Urinary Tract Infections (UTIs)

Urinary Tract Infections (UTIs) are common infections, usually caused by bacteria that affect the bladder, urethra, or kidneys.

Overview

Urinary Tract Infections (UTIs) are common infections, usually caused by bacteria, in the bladder or urethra.

There are several kinds of UTIs. The type depends on where the infection occurs. For example:

  • Urethritis is an infection in the urethra.
  • A bladder infection is called cystitis.

If left untreated, a bladder infection could travel up one or both ureters to the kidney(s), causing a kidney infection (pyelonephritis). Kidney infections can become serious and may require hospitalization as part of treatment. UTIs are not the only cause of kidney infections.

UTIs are more common among women than among men, and pregnant women are more likely to get UTIs because of a change in the position of the uterus during pregnancy. UTIs also can affect children.

Signs and Symptoms

Not every person with a UTI has symptoms, but most people notice at least one or more of the following signs:

  • Pain or stinging while urinating
  • A frequent or strong urge to urinate, while often producing only a small amount of urine
  • Milky, cloudy, dark, bloody, or foul-smelling urine
  • Lower stomach or back pain

Certain groups may have slightly different UTI symptoms, such as:

  • People with catheters (tubes inserted into the urethra to drain urine) may experience a fever with a UTI, which could indicate that the infection has reached the kidney. These women are at higher risk for kidney infections and should see their healthcare provider as soon as possible if they have a fever.
  • Older people with UTIs are more likely to feel tired, shaky, and weak and have muscle aches and abdominal pain. In some older people, a UTI can rapidly lead to a serious whole-body infection called sepsis. Sometimes the progression to sepsis can occur without a fever, so it is important that older women with UTIs receive timely initial and follow-up care.
  • UTIs can cause sudden confusion (also known as delirium) in older people and people with dementia. If the person has a sudden and unexplained change in their behavior, such as increased confusion, agitation, or withdrawal, this may be because of a UTI.

Some women may have UTI-like symptoms when they don’t actually have a UTI. These symptoms may occur because of an irritant, such as a soap or a food or drink. Once the irritant is removed or goes away, the symptoms will go away too.

Although most UTIs can be effectively treated, they should be addressed as soon as possible. Kidney infections may lead to serious problems, especially if not treated correctly. Chronic kidney infections that keep coming back or last a long time can cause permanent damage, including kidney scars, poor kidney function, high blood pressure, and kidney failure.

Acute kidney infections develop suddenly and can require hospitalization. This is especially true if the bacteria enter the bloodstream and cause a life-threatening condition called septicemia or sepsis, a whole-body infection.

When diagnosed early and treated properly, most kidney infections do not lead to complications. In rare cases, kidney infections may cause:

Your chance of a complication is slightly greater if you:

  • Are a child
  • Are male
  • Are older or frail due to weakened strength or other problems of aging
  • Are pregnant
  • Have a problem with the structure of your urinary tract
  • Have had repeat kidney infections
  • Have certain health conditions, such as diabetes, kidney disease, or sickle cell disease
  • Have a weakened immune system or have had an organ transplant

Causes and Risk Factors

A UTI develops when microbes enter the urinary tract and cause infection. Bacteria are the most common cause of UTIs, although fungi can rarely also infect the urinary tract. E. coli bacteria, which live in the bowel, cause most UTIs.

The female anatomy contributes to women’s increased likelihood of contracting a UTI. A woman’s urethra is shorter than a man’s, allowing bacteria better access to the bladder. A woman’s urethral opening is also close to sources of bacteria from the anus and vagina. Sexual activity can move bacteria to the urethral opening.

Boys younger than age 1 who have not been circumcised have a higher risk of getting UTIs than circumcised boys. The foreskin of the penis can be a source of bacteria, which can travel to the bladder. However, most uncircumcised boys do not get UTIs.

Some forms of birth control increase the risk of UTIs:

  • Spermicides can cause skin irritations that allow bacteria to invade
  • Diaphragms may slow urinary flow, encouraging bacteria to multiply
  • Unlubricated condoms or spermicidal condoms may cause irritation, which can help bacteria grow

The following factors may also encourage bacteria to grow:

  • Not drinking enough fluids
  • Purposely holding in urine for long periods of time
  • Spinal cord injuries or other nerve damage that makes the bladder difficult to empty regularly and completely
  • Conditions or situations that block the flow of urine, such as a tumor, kidney stone, enlarged prostate, or sexual intercourse
  • Diabetes and other conditions that reduce the ability of the body’s immune system to fight off infection
  • Catheters (tubes placed in the urethra and bladder to drain urine)
  • Hormonal changes pregnant women or during menopause may make it easier for bacteria to spread through the ureters and to the kidneys

Risk Factors for Kidney Infections

You are more likely to develop a kidney infection if you:

  • Are female
  • Have a current or recent bladder infection
  • Are pregnant
  • Have a urinary tract blockage, such as a kidney stone or enlarged prostate
  • Have a urinary tract problem such as vesicoureteral reflux
  • Have diabetes or problems with your immune system
  • Have a spinal cord injury or nerve damage around the bladder
  • Have trouble emptying your bladder completely, called urinary retention
  • Have an internal (ureteral stent) or external tube (nephrostomy) in the kidney
  • Are immune deficient, or use immunosuppressive medicines

Kidney infections are more common in females than males and are common during pregnancy.

Prevention Guidance

It is not always possible to prevent UTIs, but several lifestyle habits can reduce the likelihood that a person will contract a UTI:

  • Drink plenty of fluids every day, especially water, to help flush bacteria from your system
  • Do not hold in your urine for a long time
  • Urinate after sexual intercourse to flush bacteria that might have entered the urethra during sex
  • Use cotton underwear and loose-fitting clothes to circulate air and keep the area around the urethra dry (nylon underwear and tight-fitting pants can trap moisture that promotes bacterial growth)
    • For children still in diapers, changing diapers often and cleaning the genital area well with gentle cleansers that do not irritate the skin

In addition, women and girls should:

  • Wipe with toilet tissue from front to back to prevent bacteria from entering the vagina or urethra
  • Avoid using feminine hygiene sprays and soaps in the vaginal area and avoid douches

There is mixed evidence about cranberry juice for preventing UTIs. Studies have also shown that cranberry juice is not an effective treatment for an existing UTI.

Diagnosis

To diagnose a UTI, a healthcare provider will start by asking about symptoms and taking the patient’s medical history. A healthcare provider may take one or more of the following steps to help confirm the presence of a UTI:

  • Urine test: Test the urine for the presence of bacteria and white blood cells, which fight infection. The patient may need to provide a “clean catch” urine sample — washing the genital area first to prevent bacteria from getting into the sample, then catching the urine midstream in a sterile cup.
  • Urine culture: Identify the bacteria by culturing a urine sample. If the patient has recurring infections or is a hospital patient, this method makes bacteria easier to recognize by combining the urine with a substance that encourages bacteria to grow.
  • Sensitivity test: Detect bacteria by ordering a sensitivity test that can help decide which antibiotic will be most effective for treating the infection.

For recurring UTIs, healthcare providers may order one or more of the following tests to find out if the urinary tract is normal:

  • Kidney and bladder ultrasound: Bounces sound waves off the pelvic organs to create an image of their structure and reveal abnormalities
  • Voiding cystourethrogram: Creates an X-ray image of the bladder and urethra while the bladder is full and during urination; can show abnormalities inside the organs and identifies if urine flows back to the kidneys
  • Computed tomography (CT) scan: Uses X-rays and computers to create clear, detailed three-dimensional images
  • Magnetic resonance imaging (MRI): Uses radio waves and magnets rather than X-rays to produce clear, detailed images of the body’s organs and soft tissues
  • Radionuclide scan: Uses special cameras and computers to create images as a small amount of a radioactive chemical passes through the kidneys
  • Urodynamics: Determines how well the bladder, sphincter muscles, and urethra are storing and releasing urine
  • Cystoscopy: The healthcare provider inserts a tube-like instrument inside the urethra and bladder to look for a cause of infection, such as a structural anomaly

Treatment and Management

Because bacteria cause most UTIs, the usual treatment is antibiotics. The choice of medicine and length of treatment depend on the person’s age, medical history, the type of bacteria causing the infection, severity of infection, and whether the person is allergic to any antibiotics. Healthcare providers may order a sensitivity test to identify which type of bacteria are causing the infection and to help select the most effective antibiotic.

Find Clinical Trials

Clinical trials uncover better ways to prevent, diagnose, treat, and understand diseases and conditions. To ensure results apply to everyone, volunteers of all ages, sexes, and backgrounds, including both healthy individuals and those with specific medical conditions, are needed. Find clinical trials on urinary tract infections.

Research Information

The National Institutes of Health (NIH) is the largest public funder of biomedical research in the world. NIH invests most of its budget in medical research seeking to enhance life and to reduce illness and disability. NIH-funded research has led to breakthroughs and new treatments helping people live longer, healthier lives, and building the research foundation that drives discovery.

NIH conducts and supports a variety of clinical research projects on urinary tract health and on many disorders associated with it.

NIH also conducts and supports clinical trials in many diseases and conditions, including urologic diseases. Researchers study many aspects of urinary tract infections, including bladder infections, such as:

  • Antibiotic alternatives to treat UTIs
  • Alternative methods to diagnose UTIs
  • Ways to prevent repeat UTIs

Find NIH-funded research projects using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies.