What is the approach to evaluating urinalysis (Ua) results?

Urinalysis Evaluation Approach

Urinalysis evaluation requires both dipstick AND microscopic examination of a freshly voided, clean-catch, midstream urine specimen—dipstick alone is insufficient and leads to false positives and unnecessary workups. 1, 2

Initial Collection and Testing

• Obtain a freshly voided, clean-catch, midstream urine specimen to ensure accurate interpretation 1, 3
• Perform both chemical dipstick testing and microscopic sediment examination—never rely on dipstick results alone 1, 2, 3
• Laboratories should report RBC/HPF quantitatively (not just "positive" or "negative") to provide sufficient detail for clinical decision-making 1

Microscopic Examination Components

The microscopic evaluation must assess for:

• Red blood cells (RBCs): Quantify per high-powered field; ≥3 RBC/HPF defines microscopic hematuria 1, 3
• White blood cells (WBCs): Pyuria indicates genitourinary inflammation but has many noninfectious causes 4
• Crystals: Specific crystal types can be pathognomonic for stone composition (e.g., acidic pH <5.5 suggests uric acid stones) 2
• Casts: Renal tubular epithelial casts, granular casts, and hyaline casts indicate intrinsic renal disease 5
• Epithelial cells: Distinguish renal tubular epithelial cells from squamous cells 5
• Bacteria and organisms: Positive nitrites with leukocyte esterase suggest bacterial infection 2
• Dysmorphic RBCs: Indicate glomerular bleeding source 5

Clinical Context Integration

For Hematuria (≥3 RBC/HPF):

• Confirm with microscopy—dipstick measures peroxidase activity and can be confounded by povidone iodine, myoglobinuria, and dehydration 1
• Perform history and physical examination assessing risk factors for malignancy: age >35-40 years, male gender, smoking history, occupational chemical exposure, gross hematuria history, irritative voiding symptoms 1, 3
• Patients on anticoagulants require the same evaluation as those not anticoagulated—anticoagulation does not explain away hematuria 1, 3
• Rule out benign causes: urinary tract infection, menstruation, recent urologic procedures, vigorous exercise 1
• Repeat UA after treating benign causes; if hematuria persists, proceed with risk-based urologic evaluation 1
• Refer for nephrologic evaluation if medical renal disease is suspected (proteinuria, casts, dysmorphic RBCs, elevated creatinine) 1

For Suspected UTI/Dysuria:

• In healthy, nonpregnant women with classic symptoms (dysuria, frequency, urgency, suprapubic pain), diagnose and treat clinically without UA 4
• Acute-onset dysuria has >90% accuracy for UTI when vaginal irritation or discharge is absent 4
• Order UA for: frail/geriatric patients, suspected complicated UTI (structural abnormalities, immunosuppression, catheter use), suspected pyelonephritis (fever, flank pain), or recurrent UTIs 4
• Absence of pyuria helps rule out infection; presence of pyuria does NOT confirm infection (inflammation has many causes) 4
• Do not treat asymptomatic bacteriuria—this leads to unnecessary antimicrobial overuse 4

For Suspected Kidney Stones:

• Microscopic hematuria (≥3 RBCs/HPF) is the most frequent urinalysis abnormality with nephrolithiasis 2
• Acidic urine pH (<5.5) strongly suggests uric acid stone formation 2
• Positive nitrites and leukocyte esterase with alkaline pH suggest struvite (infection) stones 2
• When stone disease is suspected, obtain 24-hour urine collection measuring volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine 2

Critical Pitfalls to Avoid

• Never proceed with imaging or further investigation based on dipstick alone without microscopic confirmation of ≥3 RBC/HPF 1, 3
• Do not equate pyuria with infection—inflammation has multiple etiologies 4
• Do not dismiss hematuria in anticoagulated patients—they have similar malignancy risk 1, 3
• Avoid routine UA in febrile patients without urinary symptoms—this leads to overdiagnosis of asymptomatic bacteriuria 4
• Recognize that laboratory-performed UA may miss renal tubular epithelial cells, granular casts, RTE casts, and dysmorphic RBCs compared to nephrologist-performed examination 5