Tests
1st tests to order
urinalysis
Test
Large numbers of epithelial cells suggest contamination with vaginal microorganisms; unreliable for culture.
Sensitivity is high (72%-95%), whereas specificity is low (48%-82%).[2]
Do not define microhematuria by positive dipstick testing alone. Microhematuria is defined as three or more red blood cells per high-powered field on microscopy of a properly collected urinary specimen.[36][37]
Result
pyuria, bacteriuria, and varying degrees of hematuria; WBCs ≥10/HPF; microhematuria: red blood cells ≥3/HPF
Gram stain
Test
Gram-negative rods include Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae. E coli is the most common cause of acute uncomplicated pyelonephritis.
Gram-positive cocci include enterococci and staphylococci species.
Result
typically gram-negative rods; less typically gram-positive cocci
urine culture
Test
Properly collected clean-catch urine specimens can be cultured to identify causative agent and determine microbial sensitivity.
Urine catheter specimens are obtained in patients with inability or difficulty voiding urine, marked obesity, and redundant labia, and in ill patients who cannot reliably perform the procedure.
Specificity and sensitivity are high.
Result
bacteria ≥100,000 colony-forming units (CFU)/mL
complete blood count
Test
Leukocytosis is present in acute infection.
Result
leukocytosis
erythrocyte sedimentation rate
Test
Nonspecific marker of infection.
Result
elevated
C-reactive protein
Test
Increased in cases of bacterial infection.[40]
Result
elevated
blood culture
Test
Two sets of blood cultures drawn prior to antibiotic administration.
Sensitivity is moderate, whereas specificity is high.
Result
any bacterial growth is considered abnormal
Tests to consider
renal ultrasound
Test
Easier to schedule and less costly than other imaging modalities and does not involve exposure to radiation or dyes.[46]
Sensitivity is moderate, whereas specificity is low to moderate.
Result
gross structural abnormalities; hydronephrosis; stones; perirenal fluid collections
contrast-enhanced spiral computed tomography
Test
The test of choice when disease complications are suspected.
Sensitivity is high; specificity is moderate to high.[46]
Computed tomography of the abdomen can expose subjects to considerable radiation, but may be easier to schedule and is less expensive than magnetic resonance imaging.[45]
Result
altered renal parenchymal perfusion; altered excretion of contrast; perinephric fluid; nonrenal disease
magnetic resonance imaging
Test
Suitable alternative for patients who are allergic to iodinated dye.
Clinical experience in patients with acute pyelonephritis is limited; also cost is high.
Sensitivity is high, whereas specificity is moderate to high.[46]
Result
structural anomalies of the genitourinary system (prenatal); renal inflammation or masses; abnormal renal vasculature; urinary obstruction
procalcitonin
Test
A more specific diagnostic marker of bacterial infection; values appear to correlate with severity.[41][42] Do not perform procalcitonin testing without an established, evidence-based protocol. When used appropriately there are significant opportunities to decrease unnecessary antimicrobial use.[43]
Result
elevated
Emerging tests
interleukin
Test
Interleukins (IL-6, IL-32), as acute-phase reactants, are also being evaluated as possible markers to distinguish lower urinary tract infections from pyelonephritis.[44]
Result
elevated
copeptin
Test
A novel serum inflammatory biomarker, copeptin is the C-terminal part of pro-vasopressin (CT-pro-AVP) that is released along with vasopressin and has been investigated for use as a diagnostic tool in bacterial infections and sepsis.[40]
Result
elevated
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