What are the possible causes of red blood cells and white blood cells in urine when a urinary tract infection is absent?

Causes of Blood and White Cells in Urine Without UTI

When red blood cells (RBCs) and white blood cells (WBCs) appear together in urine without infection, you must systematically differentiate between renal parenchymal disease (glomerular causes) and urologic causes, as these require fundamentally different workups and have vastly different implications for morbidity and mortality.

Initial Diagnostic Framework

The presence of both RBCs and WBCs without infection demands immediate assessment of specific urinary findings that determine your next steps 1:

Critical Decision Point: Glomerular vs. Non-Glomerular

Evaluate for glomerular disease FIRST by examining:

• Dysmorphic RBCs: >80% dysmorphic cells indicates glomerular bleeding 1, 2
• RBC casts: Virtually pathognomonic for glomerular disease 1
• Significant proteinuria: >1,000 mg/24 hours (or >500 mg/24 hours if persistent) 1
• Elevated serum creatinine 1

If ANY of these are present, this is renal parenchymal disease requiring nephrology referral 1. Do not proceed with urologic workup first.

Glomerular/Renal Parenchymal Causes

When glomerular markers are present, consider 1:

Systemic Diseases:

• Lupus erythematosus
• Vasculitis
• Hepatitis or endocarditis-related glomerulonephritis

Primary Glomerular Diseases:

• IgA nephropathy (most common)
• Membranoproliferative glomerulonephritis
• Crescentic glomerulonephritis

Interstitial Disease:

• Drug-induced interstitial nephritis
• Analgesic nephropathy

Action: Renal biopsy is typically required if systemic causes are excluded 1.

Non-Glomerular (Urologic) Causes

If glomerular markers are absent (normal creatinine, no significant proteinuria, <80% normal-shaped RBCs, no RBC casts), proceed with complete urologic evaluation 1.

Benign Urologic Causes:

Most Common 3:

• Urolithiasis (kidney stones)
• Benign prostatic hypertrophy (men)
• Interstitial cystitis (especially women with chronic pelvic pain) 3
• Hypercalciuria/hyperuricosuria 4

Transient/Benign Causes to Exclude First 3:

• Vigorous exercise
• Recent trauma
• Menstruation
• Recent sexual activity
• Recent urologic procedure
• Indwelling catheter 5

Critical Pitfall: Repeat urinalysis 48 hours after cessation of these activities. If hematuria resolves, no further workup needed 1.

Malignant Causes (MUST BE EXCLUDED)

This is the primary reason for urologic workup 3. Risk factors include:

High-Risk Features 3, 6:

• Age >35-60 years (varies by sex and other factors)
• Male gender
• Smoking history (quantify pack-years)
• Gross hematuria (30-40% malignancy rate) 3
• Occupational chemical exposure (benzenes, aromatic amines)
• History of pelvic irradiation
• Chronic indwelling foreign body
• Analgesic abuse
• Irritative voiding symptoms

Even microscopic hematuria carries 2.6-4% malignancy risk 3.

Required Workup Algorithm

For Suspected Glomerular Disease:

1. 24-hour urine protein collection
2. Serum creatinine, BUN
3. Phase contrast microscopy for RBC morphology 2
4. Nephrology referral
5. Consider renal biopsy

For Urologic Evaluation (No Glomerular Features):

Complete urologic evaluation includes 1:

1. Upper tract imaging: CT urography (preferred) or MR urography 3
2. Cystoscopy: Essential to exclude bladder pathology 1, 7, 1
3. Urine cytology: If risk factors present (though not for initial screening) 7

Do NOT skip evaluation if patient is on anticoagulation 3. Anticoagulant therapy does not alter the need for workup.

Special Populations

Women <60 years without risk factors:

Very low malignancy risk; may observe if isolated microscopic hematuria 6

Gross hematuria (any age):

Mandatory full urologic workup regardless of other factors 3, 7

Common Pitfalls to Avoid

1. Do not treat empirically as UTI without confirming infection with culture 3
2. Do not attribute hematuria solely to anticoagulation—still requires evaluation 3
3. Do not use urinary WBC count alone to diagnose infection—poor correlation with bacteriuria 8, 9, 10, 11
4. Do not skip cystoscopy even if imaging is normal in high-risk patients 1, 7, 1
5. Do not delay nephrology referral if glomerular markers present 1

Bottom Line

The combination of RBCs and WBCs without infection represents either renal parenchymal disease requiring nephrology evaluation or urologic pathology (including malignancy) requiring imaging and cystoscopy. The presence of dysmorphic RBCs, RBC casts, significant proteinuria, or elevated creatinine immediately directs you toward nephrology. Their absence mandates urologic evaluation to exclude malignancy, stones, or structural abnormalities. Never dismiss this finding as insignificant without proper workup.