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What Is a UTI?

A urinary tract infection (UTI) occurs when bacteria or other microbes, usually fecal flora, enter the urinary tract and cause an infection. The urinary tract is the body’s system for collecting and eliminating urine and includes the kidneys, ureters, bladder, and urethra.

UTIs can affect several parts of the urinary tract. Most UTIs occur in the bladder (cystitis), but they may also involve the kidneys (pyelonephritis), urethra (urethritis), or prostate (prostatitis). UTIs are common, most frequently affecting women, resulting in more than 8.1 million visits to a doctor each year.

The Role of UTI Testing

UTI testing may be performed if a doctor suspects a UTI based on a patient’s symptoms and a physical examination. Laboratory tests can diagnose or rule out UTIs. UTI testing can also identify the bacteria or other microbes that are causing the infection, which helps doctors decide how to best treat the infection.

Types of UTI Tests

UTIs can be diagnosed by analyzing a patient’s urine sample. The two most common tests to detect UTIs are a urinalysis and a urine culture with antimicrobial susceptibility testing:

  • UrinalysisA urinalysis is a group of physical, chemical, and microscopic tests on a sample of urine. These tests look for evidence of infection, such as bacteria and white blood cells.
  • Urine cultureThis is a test that detects and identifies specific bacteria and yeast in a patient’s urine that may be causing a UTI. Urine cultures can also help doctors determine the best antibiotic for treating a UTI.
  • Susceptibility testingSusceptibility testing measures how sensitive the bacteria is to an antibiotic or antifungal drug. This helps doctors determine which treatment is most appropriate.

A UTI may be considered “complicated” if the patient is a child, is pregnant, or if their symptoms suggest that a UTI may have spread outside of the bladder. Complicated UTIs also occur in patients who have a blockage of urine flow, a health condition that increases the risk of infection or antibiotic resistance, or who have had recent surgery of the urinary tract.

In patients with a complicated UTI, additional imaging tests and blood work may be performed to rule out other issues in the urinary system:

TEST NAME PURPOSE OF TEST
Complete Blood Count (CBC) To evaluate a patient for sepsis, a severe reaction to infection
Blood Culture To assess if a UTI has spread to your blood
Sexually Transmitted Disease (STD) Testing Ordered if an STD, such as chlamydia or gonorrhea, is suspected
BUNCreatinine, Electrolytes, Lactate To evaluate the health of your kidneys and evaluate for sepsis
Urodynamic testing Tests how well your bladder, sphincters, and urethra are storing and releasing urine

Although most patients do not require imaging tests, scans and special X-rays may be ordered in children, adults who are severely ill, and anyone continuing to have symptoms after treatment is completed, as well as anyone with a suspected urinary blockage, particularly in men.

Getting Tested for a UTI

Testing for a UTI usually takes place in a doctor’s office, laboratory, or hospital. Most tests for UTIs involve a urine sample obtained by clean-catch or catheterization. Your doctor can help determine which method is appropriate for you.

  • Clean catch urine samples are collected by patients with special precautions to prevent outside germs from getting into the urine sample. Patients are given instructions on obtaining a clean catch sample and avoiding contamination.
  • Catheterization involves inserting a thin rubber tube through the urethra into the bladder. When performing this procedure, the urine is collected in a sterile container for testing before removing the catheter.

At-home testing

At-home kits are available that can detect two substances in the urine that are characteristic of a UTI: nitrites and leukocytes. Nitrites are a type of chemical, and leukocytes are white blood cells.

Using an at-home UTI test involves holding a test strip in your urine stream for several seconds and matching the resulting color of the test strip to colors indicating positive or negative test results.

At-home testing can only detect the most common types of UTIs, so a negative result does not necessarily rule out an infection. Testing for a UTI at home is not a substitute for either medical care or testing ordered by a doctor and conducted in a controlled laboratory.

Sources and Resources

To learn more about UTIs and how the affect the urinary tract, see the following web pages:

Sources

A.D.A.M. Medical Encyclopedia. Urine culture. Updated October 8, 2018. Accessed April 8, 2021. https://medlineplus.gov/ency/article/003751.htm

A.D.A.M. Medical Encyclopedia. Urinalysis. Updated February 7, 2019. Accessed April 8, 2021. https://medlineplus.gov/ency/article/003579.htm

A.D.A.M. Medical Encyclopedia. Clean catch urine sample. Updated August 13, 2020. Accessed April 8, 2021. https://medlineplus.gov/ency/article/007487.htm

A.D.A.M. Medical Encyclopedia. Urinary tract infection – adults. Updated August 13, 2020. Accessed April 8, 2021. https://medlineplus.gov/ency/article/000521.htm

Centers for Disease Control and Prevention. Urinary tract infection. Updated August 27, 2019. Accessed April 8, 2021. https://www.cdc.gov/antibiotic-use/community/for-patients/common-illnesses/uti.html

Hooton TM, Gupta K. Acute complicated urinary tract infection (including pyelonephritis) in adults. In: Calderwood SB, ed. UpToDate. Updated March 19, 2021. Accessed April 8, 2021. https://www.uptodate.com/contents/acute-complicated-urinary-tract-infection-including-pyelonephritis-in-adults

Imam TH. Bacterial urinary tract infections. Merck Manuals Professional Edition. Updated February 2020. Accessed April 8, 2021. https://www.merckmanuals.com/professional/genitourinary-disorders/urinary-tract-infections-utis/bacterial-urinary-tract-infections

MedlinePlus: National Library of Medicine. Urinary tract infections. Updated August 8, 2016. Accessed April 8, 2021. https://medlineplus.gov/urinarytractinfections.html

National Institute of Diabetes and Digestive and Kidney Diseases. Bladder infection (urinary tract infection) in adults. Updated March 2017. Accessed April 8, 2021. https://www.niddk.nih.gov/health-information/urologic-diseases/bladder-infection-uti-in-adults/all-content

US Department of Health and Human Services. Urinary tract infections. Updated April 01, 2019. Accessed April 8, 2021. https://www.womenshealth.gov/a-z-topics/urinary-tract-infections

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