A WBC count may be warranted if the emergency clinician suspects systemic illness, as this may guide treatment regimens. A creatinine level may be required before sending a patient for a computed tomography (CT) scan with contrast. If prior laboratory values have been obtained, the trending creatinine and blood urea nitrogen (BUN) values may give the emergency clinician insight as to the severity of renal pathology. There is no support in the literature to routinely order “basic” laboratory testing for patients presenting to the ED suspected of having an uncomplicated UTI. For complicated UTIs, including patients with comorbidities and immunosuppression, laboratory testing may be warranted, at the discretion of the emergency clinician
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