Tests
1st tests to order
urine dipstick
Test
Most effective in UTI with high bacterial count.
Diagnosis is more accurate if used in combination with other tests.
If the dipstick result is negative but the symptoms suggest a UTI, the probability of disease is still relatively high.[36][45][46]
Do not obtain urinalysis in older adults unless there are signs or symptoms suggestive of UTI. Asymptomatic bacteriuria is common in older patients and dipstick testing of asymptomatic patients is a cause of unnecessary antibiotic prescribing.[1][6][47] Furthermore, a positive dipstick result in asymptomatic older patients may lead to an incorrect assumption that an acute change of mental status is caused by a UTI, delaying the detection of an alternative source of infection.[47]
Result
nitrite and leukocyte esterase positive
urine microscopy
Test
Used to confirm organism type and guide antibiotic selection in complicated UTI or pyelonephritis.
Result
bacteria, WBC, possibly red blood cell
urine culture and sensitivity
Test
This is the most specific and sensitive test.
If the result is <10⁵ colony-forming units per milliliter (CFU/mL) and pyuria is present (>20 WBC/mm³) or the patient is symptomatic, the result may still be considered positive.[37][42]
Do not order urine cultures unless patients have symptoms consistent with UTI as routine culture of asymptomatic individuals may detect asymptomatic bacteriuria.[47][48] Testing for asymptomatic bacteriuria should only be pursued in specific populations such as pregnant women and those who are about to undergo endoscopic urologic procedures associated with mucosal disruption.[6]
Result
growth of >10⁵ CFU/mL
Tests to consider
postvoid residual (PVR)
Test
Indicated if urinary retention or incomplete bladder emptying is suspected.
An elevated PVR of >100 mL indicates that the patient is not emptying the bladder to completion, which may be a predisposing factor to UTI.
Result
>100 mL
renal ultrasound
Test
Only in patients in whom conventional treatment has failed or who have unusually severe or persistent symptoms.[50]
Result
kidney stone; hydronephrosis; renal abscess; renal scarring
abdominal/pelvic CT scan
Test
CT scan of the retroperitoneum can be used to rule out renal or perirenal abscess if symptoms do not respond to antimicrobial therapy after >7 days' duration.
Result
kidney or bladder stone; renal abscess
cystoscopy
Test
Used to visualize the bladder and rule out lower tract abnormalities.
Indicated only in patients in whom conventional treatment has failed or who have unusually severe or persistent symptoms.[50]
Result
tumor; bladder stone; foreign body; diverticulum
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