When is it medically appropriate to obtain a Urinalysis (UA)?

Medical Indications for Urinalysis (UA)

Urinalysis is medically appropriate in patients with suspected urinary tract pathology, unexplained fever in children, evaluation of hematuria, suspected renal disease, and as part of preoperative assessment for urologic procedures. The following are specific clinical scenarios where obtaining a urinalysis is indicated:

Evaluation of Hematuria

• Urinalysis is essential for initial evaluation of any patient with suspected hematuria 1, 2
• For microscopic hematuria (3-10 RBCs/HPF), a confirmatory repeat urinalysis is recommended to establish persistence 2
• Patients with risk factors for urologic malignancy (age >40 in men, >50 in women, smoking history >30 pack-years, occupational exposures, pelvic radiation history) should undergo UA even with minimal hematuria (1-2 RBC/HPF) 2
• After initial negative workup for asymptomatic microhematuria, yearly urinalyses should be conducted 1
• If two consecutive annual urinalyses are negative following initial evaluation, no further urinalyses for microhematuria evaluation are necessary 1

Urinary Tract Infection Evaluation

• UA is indicated in patients with symptoms suggestive of UTI (dysuria, frequency, urgency, suprapubic pain) 3
• In febrile infants and young children (2-24 months) with no obvious source of infection, UA helps determine the likelihood of UTI 1
• For children with suspected UTI, both urinalysis and urine culture are recommended, as urinalysis alone may miss 10-50% of culture-positive UTIs 1
• Collection method matters: catheterization or suprapubic aspiration is preferred for obtaining specimens in young children and infants 1
• In adults with uncomplicated UTI symptoms, positive leukocyte esterase and nitrite tests on dipstick may allow treatment without culture 4

Renal Disease Assessment

• UA is essential when evaluating for proteinuria 2
• Patients with suspected glomerular disease should have UA to assess for hematuria, proteinuria, and cellular casts 2
• UA should be obtained when evaluating patients with acute or chronic kidney disease 2
• Proteinuria quantification requires follow-up with protein-to-creatinine ratio if dipstick is positive 2

Preoperative Assessment

• UA is required prior to urologic interventions, particularly stone procedures 1
• For patients undergoing PCNL (percutaneous nephrolithotomy), UA should be obtained to screen for infection 1
• If UA suggests infection, urine culture should be obtained before proceeding with urologic procedures 1

Specific Patient Populations

• Screening UA is recommended for:
  • Adults ≥60 years of age
  • Diabetic patients of any age
  • Pregnant women
  • Adolescents 5
• Patients with gynecologic or non-malignant genitourinary conditions should have follow-up UA after resolution to confirm resolution of hematuria 1

Clinical Pitfalls and Caveats

• UA should be performed within 2 hours of collection to avoid false results from specimen degradation 4
• Cloudy urine may indicate infection but can also result from precipitated phosphate crystals in alkaline urine 4
• False positives and negatives can occur with dipstick testing; microscopic examination provides additional valuable information 4
• A negative urinalysis does not completely rule out UTI, especially in young children 1
• Urine collected by bag specimen has high contamination rates (up to 85% false positives); catheterization or suprapubic aspiration is more reliable 1
• Anticoagulation therapy does not change the approach to hematuria evaluation, as these patients have similar malignancy risk to non-anticoagulated patients 1

By following these evidence-based guidelines for obtaining urinalysis, clinicians can appropriately utilize this valuable diagnostic tool while avoiding unnecessary testing, ultimately improving patient outcomes through timely diagnosis and management of urinary tract and renal conditions.