Common laboratory tests for urinary tract infections (UTIs) include:
- Urinalysis—most UTIs are detected by performing a urinalysis, which looks for evidence of infection, such as bacteria and white blood cells in a sample of urine.
- Urine culture—for people who have recurring UTIs and those who are hospitalized, urinalysis results are confirmed with a urine culture.
- Susceptibility testing—this is done if there are microbes identified by the culture to determine which antibiotics will inhibit the growth of the bacteria or yeast causing the infection. The results will help a healthcare practitioner determine which drugs are likely to be most effective in treating a person's UTI.
One or more laboratory tests may be done as follow up in certain cases:
- If a healthcare provider suspects that a UTI may have spread into the bloodstream, a blood culture may be ordered.
- If a healthcare practitioner suspects that a person's symptoms may be due to a sexually transmitted disease, such as chlamydia or gonorrhea, then testing for one or more STDs may be performed.
- In the case of recurrent or chronic UTIs, other laboratory tests such as glucose or hemoglobin a1c (to check for diabetes) or BUN and creatinine (to evaluate kidney function) may also be done.
- If a person has had a kidney stone in addition to a UTI, then a kidney stone analysis and/or kidney stone risk panel may be done.
Imaging scans and special X-rays may be used to look for anatomical problems and/or signs of an underlying disease or condition that could be causing recurrent UTIs. Imaging tests are most often ordered for children with urinary tract infections (especially boys), adults with frequent or recurrent UTIs, and those who have blood in their urine. Each of the following imaging test provides different information about the structures of the urinary tract.
- Kidney and bladder ultrasound – sound waves are used to produce images of the bladder and kidneys so the healthcare practitioner can see any structural abnormalities.
- Voiding cystourethrogram (VCUG) – an imaging technique that allows the urethra and bladder to be viewed in real time while the bladder fills and empties
- Nuclear scans – several types of scans 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 a healthcare practitioner to look at the inner lining of the urethra and bladder. It can help identify blockages and abnormalities. If a stone is present, other instruments can be inserted through the cystoscope that may allow a stone to be removed or broken into smaller pieces with a laser. Urine and tissue samples can also be obtained using the cystoscope.
- Intravenous pyelogram (IVP) – used to look at the whole urinary tract; an opaque dye is injected into a vein, which then travels to the kidney and bladder. A series of x-rays are taken, which may reveal obstructions or structural abnormalities.