This article was last reviewed on
This article waslast modified on 7 December 2023.
What is it?

A UTI is an infection of one or more parts of the urinary tract. The urinary tract consists of two kidneys, two ureters, a bladder, and a urethra. The kidneys are bean-shaped organs found in the lower back below the ribcage. They filter waste out of the blood and produce urine to carry the waste and excess water out of the body. The urine is carried through the ureters (tubes) from the kidneys to the bladder. The bladder is a hollow muscular organ that stores urine for a short time period. The bladder stretches as urine accumulates and at a certain point it signals to the body that it needs to relieve the growing pressure. A muscular valve (sphincter) at the opening of the bladder is relaxed and the bladder contracts to send urine through the urethra (a tube linking the bladder to the external surface of a person's skin) and out of the body.

A UTI is sometimes referred to by the part of the urinary tract affected. Inflammation of the urethra (usually due to an infection but sometimes due to irritation), is called urethritis. If the bladder becomes involved it is referred to as cystitis, and if the kidneys are inflamed it is called pyelonephritis. Frequently, the blanket term UTI will be used by your doctor, because there is not a simple test that can tell exactly how much of the urinary tract is infected.

Urine does not normally contain microorganisms, but if it is obstructed from leaving the body or retained in the bladder, it provides a good environment for bacteria to grow. Most urinary tract infections are due to bacteria that are introduced into the opening of the urethra. They stick to the walls of the urethra, multiplying and moving up the urethra to the bladder. Most UTIs remain in the lower urinary tract (urethra or bladder) where they cause annoying symptoms, such as a burning sensation during urination, but are more easily treated. While these infections are easily treated in most cases, if inadequately treated, the infection may spread up through the ureters, and into the kidneys. A kidney infection is more dangerous, and can lead to permanent kidney damage - especially in young children and the elderly, in those with diabetes and those with other underlying kidney diseases. In some cases a urinary tract infection may lead to an infection in the bloodstream (sepsis, septicaemia) that can be life-threatening. Rarely, a bloodstream infection can enter the kidneys and bacteria can enter the urine from this route.

Although a variety of bacteria can cause UTIs, most (80 to 90 percent) are due to Eschericia coli, a bacterium that is common in the gut and is routinely found in faeces. Other bacteria that may cause UTIs include species of: Proteus, Klebsiella, Enterococcus and Staphylococcus. Occasionally, a UTI may be due to a yeast, such as Candida albicans. Urethritis is often due to a sexually transmitted disease such as herpes, chlamydia, or gonorrhoea.

Although anyone at any age can have a UTI, women are much more likely than men to have them. It is thought that this is partly anatomical, because a woman’s urethra is shorter (less distance for bacteria to travel) and because their anus and vagina are relatively close to the urethra. Anything that slows down the passage of the urine, blocks it, or introduces bacteria into the urinary tract can raise a patient’s risk of having a UTI. Conditions that cause an increased risk for developing a UTI include:

  • Anatomical problems (such as narrowing of the urethra or ureters)
  • Urine retention (the bladder does not empty completely)
  • Vesicoureteral reflux (the abnormal flow of urine from the bladder back to the ureters
  • Kidney stones
  • Bladder catheterisation (especially long term)
  • Spinal cord injuries
  • Diabetes (it causes changes to the immune system, damage to the kidneys and often results in sugar in the urine – promoting the growth of bacteria)
  • Kidney disease
  • Any condition that suppresses the immune system
  • In men, an enlarged prostate may reduce the flow of urine.

What are the signs and symptoms?
Although UTI symptoms vary, many people will experience:

  • A strong, persistent desire to urinate - this is called urgency.
  • Discomfort, pain, burning, tingling or stinging associated with urination – this is called dysuria. Passing urine more often than usual – this is called frequency.
  • A cloudy strong-smelling urine.
  • Passing urine more often than usual at night.
  • Lower back pain.

However, it is important remember that these symptoms could be caused by other diseases as well and not exclusive to UTI. It may need a review by a medical practitioner, like your doctor.

Those with UTIs may also have pressure in the lower abdomen and small amounts of blood in the urine. If the UTI is more severe and/or has spread into the kidneys, it may cause flank pain, high fever, shaking, chills, nausea or vomiting. Fevers are also seen when the infection spreads into the blood (sepsis). Some patients may also experience mental changes and confusion with a UTI, while others may not have any symptoms at all.

What are the complications?
In most cases UTIs are acute and uncomplicated. They are treated and the symptoms subside within a day or two. UTIs that spread to the kidneys, however, may cause permanent kidney damage, especially in the elderly and the very young. Conditions or diseases that result in chronic or recurrent UTIs may also damage to the kidneys and in some cases cause kidney failure. Kidney failure and sepsis (infection of the blood) can be life-threatening conditions. They require immediate treatment – which often involves hospitalisation. In pregnant women, a UTI can lead to premature labour and delivery and cause high blood pressure. In men, a UTI can cause prostate infection and inflammation, which can be difficult to treat.


Accordion Title
About UTI
  • Tests

    Most UTIs are diagnosed by your doctor from your symptoms. In some situations, doctors may perform  a urinalysis.  Treatment may be started at this stage.  If symptoms persist, UTI may be confirmed with a urine culture. If there are pathogenic bacteria present, then antibiotic susceptibility testing is done. This is to make sure that the antibiotic that your doctor chooses will have good activity against the bacteria causing your infection. If your doctor suspects that your infection may have spread to your bloodstream, they may refer you to hospital where they will take a blood sample for culture. If your doctor suspects that you may have a sexually transmitted disease, such as chlamydia or gonorrhoea – which may cause some of the same symptoms as a bacterial UTI – they may do additional  testing to identify them.

    In the case of recurrent or chronic urinary tract infections, other laboratory tests such as glucose (to check for diabetes), or urea and electrolytes (U&E) and creatinine (to evaluate your kidney function) may also be done. Imaging scans and special X-rays may also be used to look for anatomical problems and/or signs of an underlying disease or condition.

    Laboratory Tests
    Urinalysis. A clean (midstream) sample collection is important to minimise sample contamination by skin cells and bacteria (and, in the case of women, contamination by normal vaginal bacteria). The patient should clean their urogenital area thoroughly with soap (not anti-bacterial) and water before providing a urine specimen. White blood cells (WBC, leukocytes), red blood cells (RBC), nitrites, and bacteria in the urinalysis may indicate a UTI. It is important to know urinalysis is not reliable in older patients or those who have catheter in place.

    Urine Culture. Urine is streaked on an agar plate, then incubated for 24-48 hours. Any bacteria that grow on the agar are counted and identified. Usually if a person has a UTI, there will be a high colony count of one type of bacterium that will be present. If there are three or more types of bacteria present (or in a woman if there are vaginal bacteria, such as lactobacillus or diphtheroids) then it is considered to be a contaminated sample and no further work is done on the culture. A repeat sample may need to be submitted if the patient's symptoms persist. If there is a predominant growth of one type of bacterium present in high numbers, then antibiotic susceptibility testing is done (sometimes the doctor may refer to this as “sensitivity” testing). The ability of different antibiotics to inhibit the growth of the bacteria predicts which antibiotics will work best in the patient.

    Blood Culture. Samples of blood are taken to look for any bacteria in the blood, which is normally sterile. The blood samples are incubated in a broth medium at body temperature and examined at regular intervals for bacterial growth. Although most infections will be detected within 24 to 48 hours, if the number of bacteria is low or the bacterium is slow growing, it could take longer. Blood cultures are kept and monitored for five days. When a patient is septic from a urinary tract infection, the same microorganism is found in both the blood and the urine cultures. Antibiotic susceptibility testing will provide information on which antibiotic will eradicate the pathogen from both the blood and the urine.

    Non-Laboratory Tests
    If you have recurrent or chronic UTIs, your doctor may request one or more of the following procedures. Several may be required as they each give your doctor different information.

    Kidney and bladder ultrasound, uses sound waves to determine the structures of the bladder and the kidney, they can be seen as light and shadowed areas.

    Voiding cystourethrogram (VCUG), an x-ray test that examines the urethra and bladder while the bladder fills and empties

    Nuclear scans, several types may be used to examine the function and shape of the bladder and kidneys. For each scan type a radioactive dye is injected into a vein. The dye is carried to the bladder and kidney, allowing the visualization of any structural abnormalities.

    Cystoscopy, a flexible tube about the diameter of a straw is threaded up the urethra and into the bladder. It allows your doctor to look at the surface of the inside of urethra and bladder. It can help identify blockages and abnormalities. If a stone is present, other instruments can be inserted up through the cystoscope that may allow a stone to be removed or broken into smaller pieces with a laser. Urine and tissue sample can also be taken using the cystoscope.

    Intravenous pyelogram (IVP), used to look at the whole urinary tract. An opaque dye is injected into a vein, then travels to the kidney and bladder. A series of x-rays are taken which may reveal obstructions or structural abnormalities.


  • Prevention

    Prevention of a UTI depends on keeping the urine moving through your system and avoiding bacterial contamination of the urethra. Recommendations include:

    • Drink plenty of water every day to flush out your urinary system.
    • Urinate as you need to, don’t hold urine in for extended periods of time.
    • After a bowel movement wipe yourself from front to back to keep faecal bacteria away from the urethra.
    • Avoid irritants to the urethra if you are prone to recurrent UTIs – avoid bubble baths, take showers instead of baths, and rinse soap off thoroughly.
    • Urinate after sexual intercourse, this may help rinse out any bacteria that may have come in contact with the urethra.
    • Avoid tight clothing and wear cotton underwear – it breathes and won’t trap moisture like some synthetic fibres.
    • Drink cranberry juice – some doctors recommend this to their patients. It may help prevent bacteria from sticking to the walls of the urethra.


  • Treatment

    A UTI is usually treated with a course of antibiotics. The type, concentration, and length of antibiotic therapy will depend on:

    • Which specific bacteria is/are present
    • What drugs the bacteria is/are susceptible to
    • How much of the urinary tract is involved
    • The health / allergies of the infected patient
    • Whether or not they are having recurrent UTIs
    • Whether the infection is acute or chronic
    • Whether the antimicrobial is being used as a preventive measure or to treat an existing infection
    • Whether the infection has spread to the blood
    • Whether they are pregnant and which trimester they are in

    In a complicated UTI, your infection may be due to more than one bacterium and your doctor will need to find an antibiotic or a combination of antibiotics that will treat all of the bacteria causing the infection. If the infection has spread to the kidneys the patient may require several weeks of treatment. This is also true if the patient is a male whose prostate has become infected.

    If you are particularly prone to recurrent infections and/or particularly vulnerable to kidney damage, your doctor may recommend preventive antimicrobials, either on a continuing basis or during times of increased risk.

    If the infection is due to a sexually transmitted disease, such as chlamydia or gonorrhoea, your doctor will prescribe specific antibiotics that have been proven to be effective against these organisms. If you are sexually active and experiencing recurrent UTIs, it may be due to an asymptomatic infection in your partner. In some cases both partners will need to be treated. (If you are on oral contraceptives, you may want to talk to your doctor as some antimicrobials can lessen their effectiveness.)

    If you are on antibiotic therapy for several days, there is a chance that you may develop diarrhoea or a vaginal yeast infection. This is because the antibiotics also kill good/normal bacteria in your vagina. This upsets the balance of bacteria allowing yeast to grow in larger numbers than is usual. If this happens, talk to your doctor because you may need additional treatment.

    Sometimes recurrent or chronic UTIs will occur until an underlying structural abnormality, stone, obstruction, or disease or condition is addressed. For some conditions, surgery may be required to correct the underlying problem.