Urinary tract infection

The most obvious symptoms of urinary tract infection are a painful, burning sensation when passing urine (peeing), frequent peeing, and smelly urine (pee). Urinary tract infections are caused by bacteria entering the urethra and multiplying in the bladder. They are usually treated successfully with antibiotics prescribed by a doctor. Urinary tract infections are quite common, especially among women and children.

Causes

Normal urine is sterile and contains no germs such as bacteria, viruses, or fungi. Urinary tract infections (UTIs) occur when bacteria enter the urinary tract via the urethra. UTIs are most commonly caused by bacteria that normally live in the bowel.

The urinary tract consists of the kidneys, bladder, ureters, and urethra. The urethra is the opening to the urinary tract where urine comes out. UTIs are classified by the area of the urinary tract that is affected:

• When only the urethra is affected, it is known as urethritis
• When the bladder is affected, it is known as cystitis (the most common form of UTI)
• When the kidneys are affected, it is known as pyelonephritis (which can cause kidney damage if left untreated).

Risk factors

Females are particularly at risk of getting a UTI not because their urethra is near their anus but because their urethra is only one centimetre long, which makes it easy for the normal bacteria that live in the vagina to reach the bladder. Other factors that can increase the risk of UTIs include:

• Diabetes
• Pregnancy
• Structural defects of the urinary tract
• Being sexually active
• Any factor that obstructs urine flow e.g., kidney stones, an enlarged prostate
• Having a urinary catheter inserted into the bladder (a urinary catheter is thin tube that helps to remove urine)
• Being post-menopausal
• Using a diaphragm or spermicidal agents for birth control
• Having a weakened immune system.

UTIs are also common during childhood. The most common causes of UTIs in children are constipation, not emptying their bladder fully, and delaying peeing. Boys are more likely to develop UTIs during infancy whereas girls are more likely to develop UTIs after infancy.

Symptoms

The most common symptom of a UTI is a painful, burning sensation when passing urine. Other symptoms include:

• Pain in the abdomen or pelvic area
• Frequent peeing
• A frequent or constant urge to pee
• Cloudy or smelly urine.

When the kidneys are affected, other symptoms experienced can include:

• Back pain
• Fever and chills
• Nausea and vomiting
• Blood-stained urine.

Some people with a UTI may have no symptoms at all, while some people who have these symptoms may not have a UTI.

Symptoms of a UTI in younger children may be less clear. They include:

• Being generally unsettled
• Irritability
• Fever (with no obvious cause such as a cough)
• Not feeding well
• Abdominal pain
• Vomiting or diarrhoea.

Babies with a UTI may have no symptoms other than a fever. Older children may have pain or burning during urination and/or a need to pee frequently.

If your child is toilet trained and suddenly starts to wet their pants again, wet the bed again, or does not want to pass urine because of pain, it could be a sign of a UTI. You should see your family doctor if your baby or child has any of the signs and symptoms indicating they might have a UTI.

Because UTIs can make babies and young children seriously ill, a doctor or after-hours medical centre should be seen as soon as possible if they have one or more of the following symptoms:

• Fever
• Abdominal or back pain
• Vomiting that is persistent
• Shivering
• Drowsiness.

UTIs in the elderly can cause them to become confused and is a common cause of delirium.

Diagnosis and treatment

If a UTI is suspected, it is important to consult a doctor as soon as possible so that an accurate diagnosis can be made, and appropriate treatment given. Prompt treatment is important to prevent infection of the kidneys and other potential complications (such as sepsis) from developing. Until a doctor can be consulted, initial treatment measures include:

• Drinking lots of water
• Treating pain or fever with medications such as paracetamol.

Clinical diagnosis of a UTI is made by assessing symptoms and by analysis of the urine for the presence of bacteria and blood cells. A urine culture, which is a test that allows identification of the bacteria causing the UTI, may also be done to determine which antibiotic should be used to treat the infection.

UTIs are usually treated successfully with antibiotics. The course of antibiotics is taken orally, usually from three to ten days depending on circumstances.

Symptoms become less noticeable within 24 to 48 hours of the first dose of antibiotics being given, but it is important to finish the full course of antibiotics as prescribed, to ensure that the infection does not come back, and to prevent the infection from becoming resistant to the antibiotic (i.e., the antibiotic will not work as well if the infection returns).

With more complicated and recurrent infections there may be an underlying cause including structural abnormalities, such as urinary (vesicoureteral) reflux  in children. If an underlying cause is suspected it needs to be identified and appropriately treated where possible. Diagnostic tests that may be used include ultrasound, computerised tomography (CT) scan, magnetic resonance imaging (MRI), and specialised x-rays of the urinary tract.

In general, further tests are conducted in females aged older than 18 years who have had more than three UTIs, and in males aged older than 18 years after their first proven UTI.

If there is a history of recurrent UTIs due to a known underlying cause, a cystoscopy may be performed, which involves using a cystoscope (a long thin tube with a camera and light) to see inside the urethra and bladder. Low-dose antibiotics may be given daily for a period of weeks or months to prevent UTIs developing. If kidney infection develops, hospitalisation may be required so that antibiotics can be administered through a drip.

Prevention

The following general steps can help prevent a UTI developing:

• Drink plenty of water each day to help flush out any bacteria and avoid dehydration
• Pass urine when needed. Do not delay
• Peeing soon after sexual intercourse
• After toileting always wipe the bottom from front to back
• Shower rather than use a bath
• Do not use perfumed soaps or body wash
• Do not use sprays, powders, or douches of the genital area
• Stop smoking
• See a doctor as soon as possible if symptoms of a UTI are experienced.

References

Kidshealth (2019). Urinary tract infection (UTI) (Web Page). Auckland: Paediatric Society of New Zealand and Starship Foundation. http://www.kidshealth.org.nz/urinary-tract-infection-uti [Accessed: 28/10/22]

Krinitski, D., et al. Associations of delirium with urinary tract infections and asymptomatic bacteriuria in adults aged 65 and older: A systematic review and meta-analysis. J Am Geriatr Soc. 2021;69(11):3312-3323.

Mayo Clinic (2019). Urinary tract infection (UTI) (Web Page). Rochester, MN: Mayo Foundation for Education and Research. https://www.mayoclinic.org/diseases-conditions/urinary-tract-infection/symptoms-causes/syc-20353447 [Accessed: 28/10/22]

Ministry of Health (2017). Urinary Tract Infection (Web Page). Wellington: Ministry of Health. http://www.health.govt.nz/your-health/conditions-and-treatments/diseases-and-illnesses/urinary-problems/urinary-tract-infection [Accessed: 28/10/22]

O’Toole, M.T. (Ed.) (2017). Urinary tract infection (UTI). Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MI: Elsevier.

Weinberg, G. A. (2022). Urinary tract infection (UTI) in children (Web Page). MSD Manual Consumer Version. Kenilworth, NJ: Merck and Co., Inc. https://www.msdmanuals.com/en-nz/home/children-s-health-issues/bacterial-infections-in-infants-and-children/urinary-tract-infection-uti-in-children [Accessed 28/10/22]

Updated: October 2022