What is the evaluation and management approach for a patient with significant red blood cells (RBC) in their urine?

Evaluation and Management of Significant Red Blood Cells in Urine

The evaluation of significant red blood cells (RBC) in urine requires a comprehensive diagnostic approach including urinalysis, imaging, and cystoscopy to identify potentially serious underlying conditions, with different pathways based on whether the hematuria is glomerular or non-glomerular in origin.

Definition and Initial Assessment

• Microscopic hematuria is defined as three or more red blood cells per high-power field on microscopic evaluation of urinary sediment from two of three properly collected urinalysis specimens 1
• Dipstick detection of hematuria should always be confirmed with microscopic examination due to limited specificity (65-99%) 1
• Initial evaluation should include assessment of renal function (eGFR, creatinine, BUN) 1
• Determine if the hematuria is associated with risk factors for significant disease:
  • Smoking history
  • Occupational exposure to chemicals or dyes
  • History of gross hematuria
  • Age > 40 years
  • Previous urologic disorder or disease
  • History of irritative voiding symptoms
  • History of urinary tract infection
  • Analgesic abuse
  • History of pelvic irradiation 1

Distinguishing Glomerular from Non-Glomerular Hematuria

• Evaluate for signs of glomerular disease:

  • Presence of dysmorphic RBCs (best detected by phase contrast microscopy with 91.1% sensitivity) 2
  • Presence of RBC casts (virtually pathognomonic for glomerular bleeding) 1
  • Significant proteinuria (>1g/day) 3
  • Elevated serum creatinine 1

• Dysmorphic RBCs show variation in size and shape with irregular or distorted outlines, suggesting glomerular origin 1

• Normal doughnut-shaped RBCs generally indicate lower urinary tract bleeding 1

• Even with >40% dysmorphic RBCs, urological evaluation should not be omitted as 34% of such patients may still have urological disease, including 27.3% with clinically meaningful malignancies 4

Evaluation Pathway for Suspected Glomerular Disease

• If dysmorphic RBCs, proteinuria, cellular casts, or renal insufficiency are present, concurrent nephrologic evaluation is warranted 1, 3
• Quantify proteinuria with 24-hour urine collection (significant if >1g/day) 3
• Evaluate for systemic diseases associated with glomerulonephritis 3
• Consider renal biopsy when systemic causes are not identified 3
• Monitor renal function, proteinuria levels, and blood pressure 3

Urologic Evaluation for Non-Glomerular Hematuria

• Complete urologic evaluation includes:

  • History and physical examination
  • Laboratory analysis
  • Radiologic imaging of upper urinary tract
  • Cystoscopic examination 1

• Cystoscopy recommendations:

  • Should be performed on all patients aged 35 years and older 1
  • May be performed at physician's discretion in patients younger than 35 1
  • Should be performed regardless of age in patients with risk factors for urinary tract malignancies 1

• Imaging recommendations:

  • Multi-phasic CT urography is the imaging procedure of choice 1
  • Should include phases to evaluate renal parenchyma and urothelium of upper tracts 1

Special Considerations

• Patients on anticoagulation therapy require both urologic and nephrologic evaluation regardless of the type or level of anticoagulation 1
• Do not attribute hematuria solely to anticoagulation therapy when cellular casts and significant proteinuria are present 3
• For patients with benign causes (menstruation, vigorous exercise, sexual activity, viral illness, trauma, infection), repeat urinalysis 48 hours after cessation of the activity 1
• In women, urethral and vaginal examinations should be performed to exclude local causes; catheterized specimen may be needed if clean-catch specimen cannot be reliably obtained 1
• In uncircumcised men, the foreskin should be retracted; catheterized specimen may be required if phimosis is present 1

Follow-up Recommendations

• Patients with urinary tract infection should be treated appropriately and urinalysis repeated six weeks after treatment 1
• Patients with glomerular disease require monitoring of proteinuria levels, blood pressure, and renal function 3
• For patients with isolated hematuria and negative initial evaluation, repeat urinalysis and blood pressure checks at 6,12,24, and 36 months 5