Urinary tract infections are common infections that can affect the bladder, urethra, ureters or kidneys. Most involve the lower urinary tract, particularly the bladder and urethra, but an infection can spread to the kidneys and become more serious if it is not treated.
Common symptoms include burning or pain when urinating, a frequent or urgent need to urinate, passing small amounts of urine and discomfort in the lower abdomen. Blood in the urine can also occur.
Most UTIs are caused by bacteria entering the urinary tract through the urethra. Antibiotics are commonly used to treat bacterial UTIs, but the appropriate treatment depends on the type and severity of the infection and, in some cases, the bacteria involved.
What is a UTI?
The urinary system includes the kidneys, ureters, bladder and urethra. The kidneys produce urine, which travels through the ureters to the bladder before leaving the body through the urethra.
A UTI can occur in any part of this system. Bladder infections, also called cystitis, are the most common type. Kidney infections, known as pyelonephritis, are less common but more serious.
The distinction between upper and lower UTIs is important. Lower urinary tract infections involve the bladder and urethra, while upper urinary tract infections involve the kidneys.
Common symptoms
Symptoms vary according to where the infection occurs.
A bladder infection may cause:
- Burning or pain when urinating
- A strong or frequent urge to urinate
- Passing small amounts of urine
- Pain or pressure in the lower abdomen or pelvic area
- Cloudy, strong-smelling or bloody urine
A kidney infection can cause symptoms such as:
- Fever and chills
- Pain in the back or side
- Nausea or vomiting
- Painful or frequent urination
Kidney infection symptoms are more concerning because an infection that reaches the kidneys can cause serious complications if treatment is delayed.
Blood in the urine can occur with a UTI, but it is not specific to an infection. Other conditions can also cause blood in the urine, so it should not automatically be attributed to a UTI.
Some symptoms in the original material, including skin rashes, pain between the shoulder blades, so-called “uremic colic” and very low urine output as routine UTI symptoms, are not established typical symptoms of a UTI and have therefore been removed.
What causes a UTI?
UTIs usually develop when bacteria enter the urinary tract through the urethra and multiply. Bacteria from the gastrointestinal tract, including Escherichia coli (E. coli), are common causes of bladder infections.
Women are more likely to develop bladder infections because the female urethra is shorter and located closer to the anus, making it easier for bacteria to reach the bladder.
Other factors that can increase the risk include previous UTIs, pregnancy, menopause, diabetes, incomplete emptying of the bladder, urinary tract blockages such as kidney stones or an enlarged prostate, and use of urinary catheters. Some forms of contraception, including diaphragms and spermicides, can also increase the risk.
Acute and recurrent UTIs
UTIs are generally described as acute when they are a current infection. The term recurrent UTI is more useful than “chronic UTI” when infections repeatedly occur.
Mayo Clinic defines recurrent UTIs as two or more infections within six months or three or more within a year. Recurrent infections may require further evaluation to determine why they keep occurring.
Persistent urinary symptoms do not necessarily mean that a person has a continuing UTI. Conditions such as bladder problems, kidney stones and other urinary or genital conditions can cause similar symptoms. A healthcare professional may need urine testing and other investigations to determine the cause.
How are UTIs diagnosed?
Diagnosis generally involves a person’s symptoms and medical history, a physical examination when necessary, and urine testing.
A urinalysis can look for signs of infection, including white blood cells and blood. A urine culture can identify bacteria in the urine and help determine which antibiotics are likely to work.
For people with recurrent infections, healthcare professionals may recommend additional tests, including imaging or cystoscopy, to look for an underlying problem in the urinary tract.
A urinary symptom does not always mean that an infection is present. Symptoms can overlap with other conditions, and unnecessary antibiotic treatment can contribute to antibiotic resistance.
How are UTIs treated?
Bacterial UTIs are commonly treated with antibiotics. The choice and duration of treatment depend on factors including the location and severity of the infection, the bacteria involved, medical history and, where available, antibiotic-sensitivity results.
People prescribed antibiotics should take them according to the instructions of their healthcare professional. Stopping treatment early, sharing antibiotics or using leftover medication can contribute to antibiotic resistance.
Drinking enough fluids can help maintain hydration and may help ease symptoms, although water is not a substitute for treatment when an infection requires antibiotics. People with conditions such as kidney failure or heart disease may need individual advice about how much fluid to drink.
More serious infections, particularly kidney infections, may require hospital treatment and antibiotics given through a vein.
What happens if a UTI is not treated?
Most bladder infections do not cause complications when they are diagnosed and treated appropriately. But an untreated infection can spread from the bladder to the kidneys.
Kidney infections can cause serious illness and, in severe cases, can lead to sepsis or permanent kidney damage. This is why symptoms suggesting a kidney infection should be assessed promptly.
The risk is particularly important during pregnancy. UTIs during pregnancy can progress to kidney infection and have been associated with complications including preterm birth and low birth weight. Kidney infections during pregnancy can also cause severe maternal complications, including sepsis.
The original claim that up to 25 percent of women with recurrent UTIs develop irreversible reproductive-system damage and infertility is not supported by the sources reviewed and has therefore been removed.
When should you seek medical care?
Anyone with symptoms of a possible UTI should consider seeing a healthcare professional for assessment, particularly if symptoms are new or persistent.
Prompt medical attention is especially important when symptoms include fever, chills, back or side pain, nausea or vomiting, or other signs of a possible kidney infection.
Pregnant people with possible UTI symptoms should contact their obstetric or medical provider promptly because untreated infection can lead to complications for both the pregnant person and fetus.
Blood in the urine should also be assessed rather than automatically assumed to be caused by a UTI.
Can UTIs be prevented?
Some measures may reduce the risk of UTIs, particularly recurrent infections.
Drinking enough fluids can help maintain urinary health. Other measures include urinating when needed rather than regularly holding urine, fully emptying the bladder and, for people who are prone to UTIs after sexual activity, urinating afterward. Good hygiene practices, including wiping from front to back, can also help reduce the movement of bacteria toward the urethra.
People who experience repeated UTIs should discuss prevention with a healthcare professional. Factors such as contraception, menopause, urinary tract abnormalities and incomplete bladder emptying may need to be considered.
Cranberry products may help reduce the risk of some recurrent UTIs, but they do not treat an existing UTI, and evidence about their preventive benefit is not conclusive.
There is no good basis for claiming that reducing sugar intake, using toilet-seat covers or wearing cotton underwear prevents UTIs. Those claims in the original material have therefore not been included as established prevention measures.
The bottom line
UTIs are common and are usually treatable, but they should not simply be ignored. A bladder infection can spread to the kidneys, where it can cause a more serious infection and, in severe cases, complications such as sepsis or kidney damage.
Recognising symptoms early, getting an appropriate diagnosis and using treatment prescribed by a healthcare professional can reduce the risk of complications.
