Urinary tract infections (UTIs) account for up to 3% of emergency department visits. Urethritis and cystitis are infections of the lower urinary tract. Pyelonephritis is an infection of the upper urinary tract. Up to 80% of UTIs are caused by Escherichia coli. The rest are caused by Staphylococcus saprophyticus, Klebsiella, Proteus, Enterobacter, Pseudomonas, and Chlamydia trachomatis.
Adults at risk for UTI include women between 18 and 30 years of age, and the elderly of both sexes. Males younger than 50 years of age with symptoms of dysuria or urinary frequency usually have urethritis caused by sexually transmitted infections. UTIs in children are discussed in Chapter 75.
Typical symptoms of lower urinary tract infections are dysuria, frequency, and urgency. The addition of flank pain; costovertebral angle (CVA) tenderness; fever; and systemic symptoms, often nausea and vomiting; constitute pyelonephritis. Subclinical pyelonephritis is present in 25% to 30% of patients with cystitis. Atypical symptoms are found in patients at risk for complicated UTI. Suspect UTI in elderly or debilitated patients presenting with weakness, general malaise, generalized abdominal pain, or mental status changes. Urethral or vaginal discharge is more consistent with urethritis and vaginitis, and the possibility of a sexually transmitted disease. Asymptomatic bacteriuria is defined as two positive cultures without symptoms. Since cultures are not available acutely, asymptomatic bacteriuria is diagnosed in the emergency department when bacteria are found on microscopy in patients with no symptoms. Asymptomatic bacteriuria is commonly found in patients with indwelling catheters, up to 30% of pregnant women, and 40% of female nursing home patients. Empiric treatment is recommended for asymptomatic bacteriuria during pregnancy.
The diagnosis of UTI is based on patient symptoms and signs, with individualized assessment of urine dipstick, urinalysis, and culture in selected patients. Typically, urine dipstick and urine microscopy is performed at minimum; woman of childbearing potential should have a pregnancy test. Clean catch specimens are adequate for most patients; catheterization should be used in a patient that cannot void spontaneously, is immobilized, or is too ill or obese to be able to provide a clean voided specimen. Although the gold standard for the diagnosis is urine culture, it is not required in all cases diagnosed in the ED. Uncomplicated lower urinary tract infections (woman with symptoms, pyuria, dipstick positive for nitrite and/or leukocyte esterase) can usually be managed as an outpatient without a culture. Obtain a culture in all other cases.
Criteria for complicated UTI includes positive laboratory testing in the setting of: prior history of UTI (reoccurrence in less than 1 month or more than 3 infections per year, which defines recurrent); UTI with an atypical organism (non-E coli) or known antibiotic resistance; a functionally or anatomically abnormal urinary tract; comorbidities (metabolic diseases, carcinoma, immune suppression, sickle cell anemia); advanced neurologic disease; advanced age; nursing home residency; indwelling catheter or recent urinary tract instrumentation; pregnancy; or male sex.