I have dark reddish urine; what could be causing it and how should I be evaluated?

Dark Reddish Urine: Causes and Evaluation

You need urgent evaluation to rule out serious causes—dark reddish urine requires confirmation with microscopic urinalysis showing ≥3 red blood cells per high-power field, followed by risk-stratified urologic assessment that may include cystoscopy and imaging, particularly if you have risk factors like age >35-40 years, smoking history, or this represents visible blood. 1, 2

Immediate Confirmation Steps

• Confirm true hematuria by obtaining microscopic urinalysis on a properly collected clean-catch midstream urine specimen, as dipstick testing alone has only 65-99% specificity and can produce false positives from myoglobin, hemoglobin, food dyes, or menstrual contamination 1, 2
• The diagnostic threshold is ≥3 red blood cells per high-power field (RBC/HPF) on microscopic examination—this distinguishes true hematuria from normal findings 1, 2
• Rule out pseudohematuria from benign causes: certain foods (beets, blackberries), medications (rifampin, phenazopyridine), or myoglobinuria/hemoglobinuria which can discolor urine without actual red blood cells present 3, 4

Critical Risk Stratification

Gross (Visible) Hematuria = Urgent Urologic Referral

• Any visible blood in urine carries a 30-40% risk of malignancy and requires immediate complete urologic evaluation with cystoscopy and upper tract imaging, even if bleeding appears self-limited 1, 2
• Never delay evaluation—delays beyond 9 months are associated with worse cancer-specific survival 2
• Do not attribute hematuria to anticoagulant or antiplatelet medications without full investigation, as these drugs may unmask underlying pathology but do not cause hematuria themselves 1, 2

High-Risk Features Requiring Full Evaluation

• Age ≥35-40 years (some guidelines use 35, others 40; err on the side of caution at 35+) 1, 2
• Smoking history, particularly >30 pack-years 1, 2
• Occupational exposure to chemicals/dyes (benzenes, aromatic amines) 1, 2
• History of prior gross hematuria 1, 2
• Irritative voiding symptoms (urgency, frequency) without documented infection 1, 2
• Degree of hematuria >25 RBC/HPF 2

Distinguishing Glomerular vs. Non-Glomerular Sources

Glomerular Indicators (Kidney Disease)

• Tea-colored or cola-colored urine (not bright red) suggests glomerular bleeding 3, 2
• Significant proteinuria (>2+ on dipstick or protein-to-creatinine ratio >0.5 g/g) 3, 1
• Dysmorphic red blood cells >80% on phase-contrast microscopy 1, 5
• Red blood cell casts (pathognomonic for glomerular disease) 1, 2
• Elevated serum creatinine or declining renal function 1, 2

If glomerular features present: Nephrology referral is indicated in addition to completing urologic evaluation, as malignancy can coexist with kidney disease 1, 2

Non-Glomerular Indicators (Urologic Source)

• Bright red blood suggests lower urinary tract bleeding 2
• Absence of proteinuria or only trace amounts 2
• Normal-appearing RBCs >80% on microscopy 5
• Associated symptoms: flank pain (stones, renal mass), dysuria (infection, bladder pathology), suprapubic pain 2

Complete Diagnostic Workup for High-Risk Patients

Laboratory Evaluation

• Urinalysis with microscopy examining for dysmorphic RBCs, casts, crystals, white blood cells 1, 2
• Urine culture if infection suspected (dysuria, urgency, frequency, fever)—preferably before antibiotics 1, 2
• Serum creatinine and BUN to assess renal function 1, 2
• Complete blood count to evaluate for anemia or coagulopathy 2
• Urine cytology for high-risk patients (age >60, heavy smoking, occupational exposure) to detect high-grade urothelial cancers, though not as initial screening tool 2

Imaging

• Multiphasic CT urography is the preferred imaging modality, including unenhanced, nephrographic, and excretory phases to comprehensively evaluate kidneys, ureters, and bladder for malignancy, stones, and anatomic abnormalities 1, 2
• Renal ultrasound alone is insufficient for complete upper tract evaluation in adults with risk factors 1, 2
• If CT contraindicated (renal insufficiency, contrast allergy): MR urography or renal ultrasound with retrograde pyelography 2

Endoscopic Evaluation

• Flexible cystoscopy is mandatory for all patients with gross hematuria and for microscopic hematuria patients with risk factors, to directly visualize bladder mucosa, urethra, and ureteral orifices 1, 2
• Flexible cystoscopy preferred over rigid due to less pain with equivalent diagnostic accuracy 1, 2
• Imaging alone cannot replace cystoscopy—bladder cancer (the most common malignancy in hematuria) requires direct visualization 2

Common Causes by Category

Urologic Malignancies (30-40% of gross hematuria)

• Bladder cancer (transitional cell carcinoma)—most frequently diagnosed malignancy in hematuria cases 1, 2
• Renal cell carcinoma 2
• Upper tract urothelial carcinoma 2

Benign Urologic Causes

• Urinary tract infection—white blood cells and bacteria on urinalysis; treat and repeat UA 6 weeks later to confirm resolution 1, 2
• Urolithiasis (kidney/ureteral stones)—often presents with flank pain 3, 2
• Benign prostatic hyperplasia in men—can cause hematuria but does not exclude concurrent malignancy 2
• Trauma to kidneys or lower urinary tract 3, 2

Glomerular/Kidney Diseases

• Post-infectious glomerulonephritis (often follows strep throat) 3, 2
• IgA nephropathy 3, 2
• Alport syndrome (hereditary nephritis with hearing loss) 3, 2
• Thin basement membrane nephropathy (benign familial hematuria) 2

Transient Benign Causes

• Vigorous exercise—causes transient hematuria that resolves 48 hours after cessation 1, 2
• Menstrual contamination in women—repeat with catheterized specimen if suspected 2, 6
• Recent sexual activity 2

Follow-Up Protocol if Initial Evaluation Negative

• Repeat urinalysis at 6,12,24, and 36 months with blood pressure monitoring at each visit 1, 2
• After two consecutive negative annual urinalyses, no further testing for asymptomatic microhematuria is necessary 2
• Immediate re-evaluation warranted if:
  • Gross hematuria develops 1, 2
  • Significant increase in microscopic hematuria 1, 2
  • New urologic symptoms appear (irritative voiding, flank pain) 1, 2
  • Development of hypertension, proteinuria, or evidence of glomerular bleeding 1, 2

Critical Pitfalls to Avoid

• Never ignore gross hematuria, even if self-limited—30-40% malignancy risk mandates urgent evaluation 1, 2
• Do not defer evaluation due to anticoagulation or antiplatelet therapy—these medications unmask but do not cause hematuria 1, 2
• Do not rely solely on dipstick testing—confirm with microscopic urinalysis showing ≥3 RBCs/HPF before initiating workup 1, 2
• Do not assume single negative urinalysis excludes pathology—hematuria from cancer can be intermittent 1
• Do not delay urologic referral while waiting for other test results in patients with gross hematuria 1
• Presence of glomerular features does not eliminate need for urologic evaluation—malignancy can coexist with kidney disease 2

Special Pediatric Considerations

• Children with isolated microscopic hematuria without proteinuria or dysmorphic RBCs are unlikely to have clinically significant disease and do not require imaging 3, 2
• Renal ultrasound is the preferred initial imaging in children to assess anatomy before potential biopsy 3, 2
• CT is not appropriate for initial evaluation of isolated nonpainful, nontraumatic hematuria in children 2