# Hematuria Evaluation: Red Urine Across Ages

## Introduction

**Hematuria** -- blood in the urine -- is a common finding in both pediatric and adult medicine, with a broad differential diagnosis ranging from benign causes to life-threatening malignancy. The evaluation must be age-appropriate, as etiologies differ substantially between children and adults. Med-peds physicians must distinguish true hematuria from non-hematuria causes of red urine, differentiate glomerular from non-glomerular bleeding, and apply evidence-based evaluation strategies across the lifespan.

## Definitions and Classification

**Gross (macroscopic) hematuria**: Visible red, brown, or tea-colored urine. **Microscopic hematuria**: >=3 RBCs per high-power field on microscopic examination of centrifuged urine sediment on 2-3 separate specimens. **Transient hematuria**: Single episode; often benign (exercise, fever, dehydration) **Persistent hematuria**: Present on >=2 of 3 specimens over 2-4 weeks; warrants further evaluation.

### Non-Hematuria Causes of Red Urine

**Hemoglobinuria**: Dipstick positive for blood, but no RBCs on microscopy (hemolysis) **Myoglobinuria**: Rhabdomyolysis; dipstick positive, no RBCs, elevated CK. **Medications**: Rifampin, phenazopyridine, nitrofurantoin, doxorubicin. **Foods**: Beets (beeturia), blackberries, rhubarb. **Metabolic**: Porphyria, alkaptonuria. **Menses contamination**: Important to exclude in menstruating females.

## Glomerular vs. Non-Glomerular Hematuria

| Feature | Glomerular | Non-Glomerular |
|---------|-----------|----------------|
| Urine color | Brown, tea, or cola-colored | Bright red or pink |
| Clots | Absent | May be present |
| RBC morphology | Dysmorphic, acanthocytes | Isomorphic (normal) |
| Proteinuria | Often present | Usually absent |
| RBC casts | Present (pathognomonic) | Absent |

![Urinalysis findings distinguishing glomerular from non-glomerular hematuria](illustration-glomerular-vs-nonglomerular-hematuria.jpg)

## Pediatric Differential Diagnosis

### Glomerular Causes

**Post-infectious glomerulonephritis (PIGN)**: Most common glomerulonephritis in children; follows group A strep infection by 1-3 weeks; low C3, elevated ASO/anti-DNase B; self-limited. **IgA nephropathy**: Episodic gross hematuria during or shortly after URI ("synpharyngitic hematuria"); most common glomerulonephritis worldwide. **Alport syndrome**: X-linked or autosomal; progressive hematuria, sensorineural hearing loss, and lenticular changes; positive family history. **Henoch-Schonlein purpura (IgA vasculitis) nephritis**: Hematuria and proteinuria with palpable purpura, arthritis, abdominal pain. **Lupus nephritis**: Consider in adolescent females with multi-system involvement.

### Non-Glomerular Causes

**Urinary tract infection**: Most common cause of hematuria in children; pyuria and bacteriuria present. **Hypercalciuria**: Idiopathic; elevated urine calcium-to-creatinine ratio; may cause hematuria without stones. **Nephrolithiasis**: Less common in children than adults; evaluate for metabolic causes. **Trauma**: Renal contusion or laceration; consider non-accidental trauma in young children. **Congenital anomalies**: UPJ obstruction, polycystic kidney disease, posterior urethral valves (males) **Exercise-induced hematuria**: Benign; resolves within 48-72 hours of rest. **Wilms tumor**: Rare but important; typically presents in children aged 1-5 with abdominal mass.

## Adult Differential Diagnosis

### Glomerular Causes

**IgA nephropathy**: Most common glomerulonephritis; episodic hematuria with URI. **Membranoproliferative glomerulonephritis**: Associated with hepatitis C, cryoglobulinemia. **Anti-GBM disease (Goodpasture syndrome)**: Pulmonary hemorrhage and rapidly progressive glomerulonephritis. **ANCA-associated vasculitis**: Granulomatosis with polyangiitis, microscopic polyangiitis.

### Non-Glomerular Causes

**Urinary tract malignancy**: **Bladder cancer** is the most important cause to exclude in adults over 35 with hematuria; risk factors include smoking, occupational exposures. **Nephrolithiasis**: Common in adults aged 20-50; flank pain, colicky nature. **UTI/pyelonephritis**: Dysuria, frequency, and pyuria. **BPH**: Prostatic enlargement causing hematuria in older men. **Renal cell carcinoma**: Classic triad of hematuria, flank pain, and palpable mass (present in <10%) **Anticoagulation**: Does not cause hematuria de novo; unmasks underlying pathology that requires evaluation. **Polycystic kidney disease**: Autosomal dominant; cyst rupture or infection.

## Evaluation Approach

### Pediatric Evaluation

**Urinalysis with microscopy**: Confirm true hematuria; assess for casts, dysmorphic RBCs, proteinuria. **Urine culture**: Exclude infection. **Serum creatinine, BUN, albumin**: Assess renal function. **Complement levels (C3, C4)**: Low C3 in PIGN, MPGN, lupus nephritis. **Urine calcium-to-creatinine ratio**: Screen for hypercalciuria (>0.2 in children >2 years) **Renal ultrasound**: Evaluate anatomy, stones, masses, cystic disease. **Referral to pediatric nephrology**: For persistent hematuria with proteinuria, dysmorphic RBCs, or abnormal renal function.

### Adult Evaluation

**Urinalysis with microscopy**: Characterize hematuria type. **Urine cytology**: For patients at risk for urothelial carcinoma. **CT urogram**: Preferred imaging for adults with unexplained hematuria; evaluates upper tracts. **Cystoscopy**: Recommended for all adults >=35 years with unexplained microscopic or gross hematuria (AUA guidelines) **Renal function tests**: Creatinine, eGFR. **Nephrology referral**: For glomerular hematuria (dysmorphic RBCs, RBC casts, proteinuria) **Urology referral**: For non-glomerular hematuria in adults, especially >=35 years, for cystoscopy and upper tract imaging.

![Age-appropriate evaluation algorithm for hematuria](illustration-hematuria-evaluation-algorithm.jpg)

## Special Considerations

**Sickle cell trait and disease**: Common cause of hematuria in Black patients; papillary necrosis and renal medullary carcinoma are serious complications. **Thin basement membrane nephropathy**: Benign familial hematuria with excellent prognosis; distinguished from early Alport syndrome by genetic testing. **Nutcracker syndrome**: Compression of left renal vein between aorta and SMA; causes left-sided hematuria, more common in thin individuals.

![Causes of hematuria organized by anatomic location](illustration-hematuria-anatomic-causes.jpg)

## Clinical Pearls

Always confirm hematuria with microscopy; dipstick-positive results may reflect hemoglobinuria or myoglobinuria rather than true hematuria. RBC casts are pathognomonic for glomerulonephritis; dysmorphic RBCs suggest glomerular origin. In adults over 35, unexplained hematuria requires cystoscopy and upper tract imaging to exclude malignancy regardless of anticoagulation status. Post-infectious glomerulonephritis is the most common glomerulonephritis in children and typically resolves spontaneously with normalization of C3 within 6-8 weeks. Hematuria in a patient on anticoagulation still requires full evaluation; anticoagulation unmasks but does not cause urinary tract pathology.

## References

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3. Yuste C, Gutierrez E, Sevillano AM, et al. Pathogenesis of glomerular haematuria. *World J Nephrol*. 2015;4(2):185-195.
4. Massengill SF. Hematuria. *Pediatr Rev*. 2008;29(10):342-348.