What is urine with microscopic findings?

What is Urine with Microscopic Findings?

Urine with microscopic findings refers to urine that contains red blood cells (≥3 RBCs per high-power field) or other cellular elements visible only under microscopic examination, not visible to the naked eye—this is termed microscopic hematuria and requires systematic evaluation to exclude malignancy and renal disease. 1

Definition and Detection

Microscopic hematuria is defined as the presence of three or more red blood cells per high-power field on microscopic evaluation of urinary sediment from two of three properly collected specimens. 2, 3

• Dipstick testing alone is insufficient for diagnosis due to limited specificity (65-99%), and microscopic examination is required to confirm true hematuria. 2
• The microscopic examination is vital for diagnosis, as approximately 15-30% of urines with negative macroscopic findings reveal significant abnormalities microscopically. 4
• Microscopic hematuria has a prevalence of 0.19-21% in the general population, with higher rates in older individuals. 2, 5

Key Microscopic Findings and Their Significance

Red Blood Cell Morphology

• Dysmorphic RBCs (>80%) indicate glomerular bleeding and suggest renal parenchymal disease such as glomerulonephritis. 2, 6
• Normal "doughnut-shaped" RBCs (>80%) suggest lower urinary tract bleeding from non-glomerular sources. 2
• Phase contrast microscopy is superior to bright field microscopy for identifying dysmorphic red blood cells. 7

Additional Cellular Elements

• Red blood cell casts are pathognomonic for glomerular disease and warrant nephrology referral. 1, 2
• White blood cells and micro-organisms indicate urinary tract infection, which should be treated with antibiotics and urinalysis repeated 6 weeks after treatment. 1
• Proteinuria (>2+ by dipstick) accompanying hematuria suggests glomerular pathology. 1
• Crystals may provide clues to drug-related or toxin-related acute kidney injury, or inherited conditions like adenine phosphoribosyltransferase deficiency. 7

Clinical Significance and Risk Stratification

Malignancy Risk

• Microscopic hematuria carries a 2.6-5% risk of urinary tract malignancy, significantly lower than gross hematuria (30-40%) but still requiring thorough evaluation. 2, 3
• Urothelial cancers (transitional cell carcinoma) are the most commonly detected malignancies in patients with microscopic hematuria. 1

High-Risk Features Requiring Urologic Evaluation

• Age >40 years 2, 6
• Smoking history 2, 6
• Occupational exposure to chemicals or dyes (benzenes, aromatic amines) 6
• History of gross hematuria 2

• 25 RBC/HPF 8

• Irritative voiding symptoms 6
• History of pelvic irradiation 6

Evaluation Algorithm

Initial Laboratory Assessment

1. Comprehensive urinary sediment examination to determine RBC count per high-power field and identify dysmorphic RBCs or casts. 1
2. Test for proteinuria and measure serum creatinine to assess renal function. 1, 2
3. Urine culture if infection is suspected; treat and recheck urinalysis 6 weeks post-treatment. 1, 6

Differentiation of Glomerular vs. Non-Glomerular Sources

Glomerular bleeding indicators (requiring nephrology referral):

• Proteinuria >500 mg/24 hours 2, 6
• Dysmorphic RBCs >80% 2, 6
• Red cell casts 2, 6
• Elevated serum creatinine 2, 6

Non-glomerular bleeding (requiring urologic evaluation):

• Normal RBC morphology 2
• Absence of proteinuria, casts, or renal dysfunction 2

Imaging and Cystoscopy for Non-Glomerular Hematuria

• CT urography is the preferred imaging modality for high-risk patients to detect renal cell carcinoma, transitional cell carcinoma, and urolithiasis. 2, 8
• Cystoscopy is essential for evaluating the lower urinary tract for bladder masses, urethral strictures, and benign prostatic hyperplasia. 3
• Voided urine cytology is recommended for patients with risk factors for transitional cell carcinoma. 1

Important Clinical Pitfalls

• Do not attribute microscopic hematuria to anticoagulation therapy (including Pradaxa) without proper evaluation, as patients on anticoagulants have similar malignancy risk. 2, 8
• Do not assume hematuria in women is due to menstruation without verification through repeat testing after menstruation. 2, 6
• Do not omit evaluation in patients with benign prostatic hyperplasia, as BPH does not exclude malignancy. 8
• Exclude benign causes (menstruation, vigorous exercise, sexual activity, viral illness, trauma) before extensive workup, and repeat urinalysis 48 hours after cessation of the potential cause. 2, 6

Follow-Up for Persistent Hematuria

For patients with negative initial evaluation but persistent microscopic hematuria:

• Repeat urinalysis at 6,12,24, and 36 months 8, 6
• Monitor blood pressure 6
• Consider nephrology referral if hematuria persists with development of hypertension, proteinuria, or glomerular bleeding indicators 8, 6