Approach

Treatment can be initiated based on both symptomatic diagnosis and urinalysis results. Urine culture and sensitivity confirms diagnosis and determines selection of appropriate antibiotics.[39] Quality standards and guidelines should be considered when evaluating and treating suspected urinary tract infections (UTIs).[40][41][42]​​​​​[43]

Clinical evaluation

The probability of UTI in primary care settings in women with one or more symptoms of UTI (dysuria, urinary urgency, urinary frequency, suprapubic pain, back pain, or gross hematuria) is about 50%.[36] Other symptoms suggestive of upper tract involvement (such as pyelonephritis) include fever and/or costovertebral tenderness. In the elderly population, symptoms are often atypical and can include hypotension, tachycardia, urinary incontinence, poor appetite, drowsiness, frequent falls, and delirium.[44]

Dipstick analysis

Dipstick urinalysis is considered as the first diagnostic test in women with urinary tract symptoms. The combination of positive nitrite and leukocyte esterase in the urine indicates a likely diagnosis of UTI.[36] However, 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]​​ 

In the absence of an acute UTI, dipstick tests positive for blood require a microscopic urinalysis to delineate between true microhematuria (presence of >3 RBCs per high-power field on 2 urine specimens) and hemoglobinuria (positive heme on dipstick in the absence of red blood cells). Microhematuria in the absence of UTI requires further evaluation to determine the etiology.

Urine microscopy and culture

A midstream clean-catch urine specimen should be sent for culture in patients with atypical symptoms, unexpected findings on urinalysis, suspected pyelonephritis, and women whose symptoms do not resolve or whose symptoms recur within 2 to 4 weeks of treatment.[37] Culture also can be used to obtain pretreatment antibiotic sensitivities in women with a history of recent antimicrobial therapy, with symptoms >7 days, age >65 years, people with diabetes, or pregnant women. 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]

Growth of a single uropathogen at a quantity as low as 100 colony-forming units per milliliter (CFU/mL) may indicate a significant infection in a symptomatic woman that requires antibiotic treatment.[49] 

A Gram stain can be used to confirm organism type and guide antibiotic selection in complicated UTI or pyelonephritis.

Imaging

Uncomplicated UTI does not usually require radiologic evaluation unless it is recurrent; imaging should, in general, be reserved for those patients in whom conventional treatment has failed or who have unusually severe or persistent symptoms.[50] Upper urinary tract abnormalities are not common with bacterial cystitis in healthy women, and therefore the routine use of scans is not indicated.

Renal ultrasound and abdominal/pelvic computed tomography (CT) scan can be used to rule out upper tract abnormalities, including kidney stone, hydronephrosis, renal abscess, or renal scarring.

Consider imaging for women with:​[1]​​[2]

  • Unexplained or persistent hematuria, obstructive symptoms, neurogenic bladder dysfunction, and a history of urinary calculi, analgesic abuse, or diabetes mellitus

  • A complicated UTI, to rule out structural abnormalities, tumor, or stone

  • Recurrent UTI with breakthrough UTIs despite prophylaxis

  • A persistent bacterial infection despite adequate treatment.

A CT scan of the retroperitoneum should be used to rule out renal or perirenal abscess if symptoms do not respond to antimicrobial therapy or if >7 days' duration.[19]

Cystoscopy

Cystoscopy can be used to visualize the bladder and rule out lower tract abnormalities such as a tumor, bladder stone, foreign body, or diverticulum, and is indicated for the same reasons noted for ordering an imaging study.

Postvoid residual (PVR)

If urinary retention or incomplete bladder emptying is suspected after resolution of a current UTI, or in someone with recurrent UTI, a PVR can be done to observe if the bladder is emptying normally. An elevated PVR of >100 mL indicates that the patient is not emptying the bladder to completion, which may promote infection and may be a predisposing factor to UTI. If abnormal emptying is observed, further evaluation may be undertaken to investigate the cause.

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