Urinary tract infections are caused by microbes such as bacteria overcoming the body's defenses in the urinary tract. They can affect the kidneys, bladder, and the tubes that run between them.
They are one of the most common types of infection and account for around 8.1 million visits to doctors each year.
The urinary tract is responsible for removing waste and excess water from the body. It consists of the bladder, the kidneys, the ureters, and the urethra.
The kidneys filter the blood and remove waste and surplus water to form urine, which then travels down the ureters and is stored in the bladder until it is ready to be passed through the urethra (urination).
The opening of the urethra is the end of the penis in males and at the front of the vagina in females. The urinary tract can be divided into the upper urinary tract and the lower urinary tract. The upper urinary tract consists of the kidneys and the ureters, and the lower urinary tract consists of the bladder and the urethra.
Here are some key points about urinary tract infection. More detail and supporting information is in the main article.
- Women have a lifetime risk of over 50 percent of developing a urinary tract infection
- Common symptoms include a strong, frequent urge to urinate and a painful and burning sensation when urinating
- Urinary tract infection is usually diagnosed based on symptoms and testing of a urine sample
- Uncomplicated urinary tract infections can be cured with 2-3 days of treatment
- Cranberry extracts do not treat UTIs but may help reduce the risk of recurrent UTI
What is a urinary tract infection?
The urinary tract is comprised of the bladder, kidneys, ureters, and urethra.
A urinary tract infection (UTI) is an infection of any part of the urinary system. Most infections involve the lower urinary tract. UTIs are given different names depending on where they occur:
The ureters are very rarely the site of infection.
Women are more likely to develop UTIs than men, due to anatomical differences; the urethra is shorter in women than in men, and it is closer to the anus, making it more likely that bacteria are transferred to the bladder.
Over 50 percent of all women will experience at least one UTI during their lifetime, with 20-30 percent experiencing recurrent UTIs.
Pregnant women are not more likely to develop a UTI than other women, but if one does occur, it is more likely to travel up to the kidneys; this is because of anatomical changes during pregnancy that affect the urinary tract.
As a UTI in pregnancy can prove dangerous for both maternal and infant health, most pregnant women are tested for the presence of bacteria in their urine, even if there are no symptoms, and treated with antibiotics to prevent spread.
Most UTIs are not serious, but some can lead to serious problems, particularly with upper urinary tract infections. Recurrent or long-lasting kidney infections (chronic) can cause permanent damage, and some sudden kidney infections (acute) can be life-threatening, particularly if septicemia (bacteria entering the bloodstream) occurs.
They can also increase the risk of women delivering low birth weight or premature infants.
Causes of urinary tract infections
The vast majority of UTI cases are caused by the bacterium Escherichia coli (E. coli), usually found in the digestive system. Chlamydia and Mycoplasma bacteria can infect the urethra but not the bladder.
People of any age and sex can develop a UTI; however, some people are more at risk than others. The following factors can increase the likelihood of developing a UTI:
- Sexual intercourse (especially if more frequent, intense, and with multiple or new partners)
- Poor personal hygiene
- Problems emptying the bladder completely
- Having a urinary catheter
- Bowel incontinence
- Blocked flow of urine
- Kidney stones
- Some forms of contraception
- Procedures involving the urinary tract
- Suppressed immune system
- Immobility for a long period
- Use of spermicides and tampons
- Heavy use of antibiotics (which can disrupt the natural flora of the bowel and urinary tract)
Symptoms of urinary tract infections
Abdominal pains are a common symptom of urinary tract infections.
The symptoms of a urinary tract infection can depend on age, gender, the presence of a catheter, and what part of the urinary tract has been infected.
Common symptoms of urinary tract infection include:
- Strong and frequent urge to urinate
- Cloudy, bloody, or strong smelling urine
- Pain or burning sensation when urinating
- Nausea and vomiting
- Muscle aches and abdominal pains
People with catheters may only experience fever as a symptom, making diagnosis more difficult.
Acute pyelonephritis is a sudden and severe kidney infection. If an individual develops this condition they could also experience upper back and side pain, high fever, shaking, chills, fatigue, and mental changes. It is considered an emergency and should be evaluated by a doctor immediately if suspected.
If a person has a bladder infection, they could also experience low fever, and pressure and cramping in the abdomen and lower back.
Tests and diagnosis
Diagnosis will usually be made after asking about the symptoms and testing a urine sample to assess the presence of white blood cells, red blood cells, and bacteria. A method of collecting urine called "clean catch" is used, which is where a person washes their genital area before collecting a urine sample mid-flow. This helps to prevent bacteria from around the genital area getting caught in the sample.
If a person has recurrent UTIs, a doctor may request further diagnostic testing to determine if anatomical issues or functional issues are to blame. Such tests may include:
- Diagnostic imaging - assessing the urinary tract using ultrasound, CT and MRI scanning, radiation tracking, or X-rays
- Urodynamics - a procedure that determines how well the urinary tract is storing and releasing urine
- Cystoscopy - looking inside the bladder and urethra with a camera lens inserted via the urethra through a long thin tube
Treatment of urinary tract infections
Drinking plenty of water helps flush out urinary tract infections and lowers the risk of future infection.
As urinary tract infections are normally caused by bacteria, they are most commonly treated with antibiotics or antimicrobials. The type of medication and length of treatment will depend on the patient's symptoms and history.
The full course of treatment should always be completed for UTIs to make sure that the infection is fully clear, and to reduce the risk of antibiotic resistance. UTI symptoms can disappear before the infection has completely gone.
Drinking lots of fluids and frequently urinating are always recommended for people who have UTIs as this helps to flush out the bacteria. A variety of pain relief medications may be prescribed to alleviate pain. Applying a heating pad to the back or abdomen can also help.
An uncomplicated UTI is one that occurs in an otherwise healthy person with a normal clear urinary tract. These can usually be cured with 2-3 days of treatment.
A complicated UTI is one that occurs in a person who is weakened by another condition, such as pregnancy or heart transplant. Complicated UTIs tend to require longer periods of antibiotics, usually between 7-14 days.
To cure a UTI that is caused by problems within the urinary system, the underlying issue needs to be found and corrected. If left untreated, these infections can lead to kidney damage.
If the patient is seriously ill, they may need to be admitted to a hospital to ensure that they take in sufficient fluids and receive the right medication. Patients may also need to go to the hospital if they:
- Are pregnant and are otherwise ill
- Are elderly
- Have cancer, diabetes, multiple sclerosis, spinal cord injury, or other medical problems
- Have kidney stones or other changes in the anatomy of their urinary tract
- Have recently undergone urinary tract surgery
Recurrent infections in women
Women who have recurrent bladder infections may be advised to:
- Take a single dose of an antibiotic after sexual contact
- Take a single, daily dose of an antibiotic for at least 6 months
- Take a short course - 2-3 days - of an antibiotic if symptoms reappear
- Have vaginal estrogen therapy if postmenopausal
There are several measures that can be taken to reduce the risk of developing a UTI:
- Drink lots of water and urinate frequently
- Avoid fluids such as alcohol and caffeine that can irritate the bladder
- Urinate shortly after sex
- Wipe from front to back after urinating and bowel movement
- Keep the genital area clean
- Showers are preferred to baths and avoid using oils
- Sanitary pads or menstrual cups are preferred to tampons
- Avoid using a diaphragm or spermicide for birth control
- Avoid using any perfumed products in the genital area
- Wear cotton underwear and loose-fitting clothing to keep the area around the urethra dry
Individuals are advised to contact a doctor if they develop the symptoms of a UTI, especially if they have developed the symptoms of a potential kidney infection (acute pyelonephritis).
Cranberry, probiotics, and UTIs
Cranberry extracts do not help treat existing UTIs but may help prevent the development of UTIs. This is because cranberries contain compounds (proanthocyanidins) that prevent E. coli from sticking to the walls of the digestive and urinary tract.
In a large meta-analysis, researchers found that women with recurrent UTIs who took cranberry over 12 months had a 35 percent reduction in infections. One large clinical trial found that 500 milligrams of cranberry extract taken daily for 6 months reduced the rate of UTI to the same extent as trimethoprim 100 milligrams, without posing a risk of antimicrobial resistance or super-infection in women with recurrent UTIs.
Cranberry extract tablets appear to be twice as effective as cranberry juice for preventing UTIs, which may be due in part to the sugar content of cranberry juice. Cranberry extracts also contain anthocyanins and salicylic acid, which may exert an analgesic and anti-inflammatory effect that can help alleviate UTI symptoms.
The Society of Obstetricians and Gynaecologists of Canada recommend cranberry products to prevent recurrent UTIs, but not for use in active UTIs.
Changes in the bacterial balance of the genitourinary tract can increase the likelihood of colonization by organisms such as E. coli. Regular use of probiotics may help reduce the risk of UTIs, especially after a course of antibiotics.
In particular, Bifidobacterium longum has shown an ability to prevent undesirable bacteria sticking to the walls of the intestinal tract, in addition to enhancing production of natural antibacterial chemicals and organic acids, thereby reducing the likelihood of UTI.