Chapter 53. Urinary Tract Infections and Hematuria

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.

The urine nitrite reaction is greater than 90% specific but only about 50% sensitive in the diagnosis of UTI. A positive result with symptoms and bacteriuria is confirmatory. UTI with Enterococcus, Pseudomonas or Acineobacter results in a negative nitrite test. The leukocyte esterase reaction is more sensitive (77%) but less specific (54%) than the nitrite reaction. If it is positive, it is supportive of UTI. In summary, a positive urine dipstick nitrate or leukocyte test result supports the diagnosis of UTI; a negative test result does not exclude it.

A urine white blood count per high power field (WBC/HPF) of greater than 2 to 5 cells in women and 1 to 2 cells in men, in a patient with appropriate symptoms, is suggestive of a UTI. In a symptomatic patient with less than 5 WBC/HPF, one must consider causes of false-negative pyuria. These include dilute urine, systemic leukopenia, partially treated UTI, and obstruction of an infected kidney. Any bacteria on an uncentrifuged specimen is abnormal, and more than 1 to 2 bacteria per HPF in a centrifuged specimen is 95% sensitive and more than 60% specific for UTI. False- negative results may occur in a low colony count infection or in the case of Chlamydia. False-positive results may occur due to contamination with fecal or vaginal flora.

In patients with urinary catheters, the diagnosis of UTI is difficult as both pyuria and asymptomatic bacteruria are near-universal by the fourth 4 week indwelling. Treatment is only recommended in symptomatic patients; see Chapter 57 for detailed criteria of symptomatic catheter-associated infection. Renal imaging should be considered acutely in the severely ill, if there is suspicion for a stone associated with infection, and with a poor initial response to therapy.

Differential diagnostic considerations include: upper and lower urinary tract infections, urethritis due to sexually transmitted infections (which are more common than cystitis/pyelonephritis in males younger than 50 years of age), vaginitis, (both sexually and nonsexually transmitted), vulvodynia, prostatitis, epididymitis, and intraabdominal pathology.

Treatment is determined by whether the urinary tract infection is complicated or uncomplicated.

Acute pyelonephritis can be treated as an outpatient if the patient has normal anatomy and is otherwise healthy. Urine culture, larger doses, and longer duration of antibiotics are recommended.

1. Uncomplicated UTI. Empiric treatment is best based on local resistance patterns. For uncomplicated lower urinary tract infections in women, TMP-SMX DS (160/800 milligrams twice a day for 3- to 5-days) is recommended as first choice in areas, where E coli resistance is less than 20%. However, 20% to 30% of patients given 3- to 5-day therapy will experience treatment failure or rapid relapse. Nitrofurantoin (100 milligrams 4 times a day or 100 milligrams extended release twice a day for 5 days) is a first-choice antibiotic with lower resistance. Nitrofurantoin is recommended for asymptomatic bacteriuria during pregnancy.

2. Complicated UTI. Use fluoroquinolones (ciprofloxacin 500 milligrams twice a day or levofloxacin 500 milligrams once a day), cefpodoxime (200 milligrams twice a day), or fosfomycin (3 grams once), in males, cases where symptoms suggest upper urinary tract involvement or have been present for more than a week, infection is recurrent, follow-up is unsure, there are complicating factors, or local resistance to TMP-SMX is greater than 20%. Duration of therapy should be 10 to 14 days. Ciprofloxacin resistance may preclude its effective use in some communities.

3. Use caution with nitrofurantoin and the fluoroquinolones in the elderly and in patients with renal insufficiency.

4. If there is suspicion for concomitant infection with gonorrhea and/or Chlamydia, antibiotic choice is more complex. (See Chapter 87 “Sexually Transmitted Diseases”).

5. Consider 1 to 2 days of an oral bladder analgesic such as phenazopyridine 200 milligrams, 3 times a day.

6. Discharge instructions must include instructions to return for increased pain, fever, vomiting or intolerance of medications, to take the entire course of antibiotics, and to follow up with primary care provider. Encourage fluids, (cranberry juice may be helpful), and frequent voiding.

7. Admission is indicated for pyelonephritis associated with intractable vomiting and should be considered for complicated UTIs. Empiric antibiotic therapy should be initiated in the ED: ciprofloxacin 400 milligrams IV every 12 hours, ceftriaxone, 1 gram IV once daily, gentamicin, or tobramycin, 3.0 milligrams/kilogram/d divided every 8 hours ± ampicillin 1 to 2 grams every 4 hours. For patients with unstable vital signs, see Chapter 89 “Septic Shock”.

Hematuria is blood in the urine. It is either visible to the eye, gross hematuria, requiring 1 mL of whole blood per liter; or microscopic, only seen under the microscope, defined as greater than 3 to 5 RBCs per HPF.

Clinical Features

Gross hematuria suggests a lower urinary tract source; microscopic hematuria suggests a renal source. Asymptomatic hematuria is more often due to neoplasm or vascular causes than infection. Asymptomatic hematuria is defined as greater than 3 to 5 RBCs per HPF on 2 of 3 properly collected urine specimens in a patient with no symptoms.

Diagnosis and Differential

A urine dipstick is positive with approximately 5 to 20 red blood cells per mL of urine. All positive dipsticks should be followed by microscopy. False-positive results can occur with the presence of myoglobin, porphyrins, free hemoglobin (as opposed to intact RBCs) due to hemolysis, and povidone-iodine. Catheterization usually does not cause an abnormal result. False-negative results can be seen with very high specific gravity. Differential diagnostic considerations are numerous. Consider the patients' age, sex, demographic characteristics, habits, potential risk factors for urologic malignancy, comorbidities, or any history of recent urinary tract instrumentation. The most common causes of hematuria are UTI, nephrolithiasis, neoplasms, benign prostatic hypertrophy, glomerulonephritis, and schistosomiasis (most common cause worldwide). In the ED, consider strenuous exercise, poststreptococcal infection (in younger patients) and life threats including malignant hypertension, eroding abdominal aortic aneurysm, coagulopathy, foreign body, immune-mediated disease (Henoch-Schönlein purpura, pulmonary-renal syndromes), sickle cell disease complications, and renal vein thrombosis.

Emergency Department Care and Disposition

1. Treatment of hematuria is directed at the cause. ED management consists of the minimization of complications and appropriate referral or admission for further evaluation.

2. All hematuria should be followed up by either primary care or urology within 2 weeks.

3. Admit patients with infection associated with an obstructive stone, intractable pain, intolerance of medications or oral fluids, newly diagnosed glomerular nephritis, significant anemia, renal insufficiency, significant comorbidity, bladder outlet obstruction, pregnancy with preeclampsia, pyelonephritis, obstructive stone; or any potentially life-threatening causes of hematuria.