What are the common causes of hematuria in children?

Causes of Hematuria in Children

The most common causes of hematuria in children are urinary tract infection, glomerulonephritis (particularly post-infectious and IgA nephropathy), and hypercalciuria, with malignancy being exceedingly rare compared to adults. 1, 2, 3

Primary Etiologic Categories

Infectious Causes

• Urinary tract infection is one of the most frequent causes of both microscopic and macroscopic hematuria in children, identified by white blood cells and microorganisms in urinalysis 1, 2
• Post-infectious glomerulonephritis occurs 7-21 days after streptococcal infection, presents with tea-colored urine, proteinuria, and low C3 levels that normalize by 8 weeks, and typically resolves over 6-12 months 4

Glomerular/Renal Parenchymal Causes

• IgA nephropathy (Berger disease) is the most common glomerular cause requiring renal biopsy for definitive diagnosis, often presenting with recurrent gross hematuria following upper respiratory infections 1, 5
• Alport syndrome (hereditary nephritis) should be suspected with family history of kidney disease or hearing loss, requiring audiogram and slit lamp examination 1, 2
• Thin basement membrane nephropathy is an autosomal dominant condition representing the most common cause of benign familial hematuria, diagnosed by screening family members' urine 1, 2
• Henoch-Schönlein purpura presents with hematuria accompanied by rash, arthritis, and soft-tissue edema 1, 6

Metabolic Causes

• Hypercalciuria is the most common identifiable cause in children with both microscopic (16%) and gross hematuria (22%), evaluated by spot urine calcium-to-creatinine ratio 2, 5
• Hyperuricosuria can cause microscopic hematuria and predispose to nephrolithiasis 1

Urologic/Structural Causes

• Congenital urologic anomalies occur in approximately 13% of children with gross hematuria, including vesicoureteral reflux, ureteropelvic junction obstruction, posterior urethral valves, and ureterocele 7
• Urolithiasis accounts for approximately 5% of cases, detected by renal ultrasound or plain radiography for radiopaque stones 1, 7
• Nutcracker syndrome (left renal vein compression) causes hematuria with variable proteinuria, diagnosed by ultrasound with Doppler 8

Trauma-Related Causes

• Blunt or penetrating trauma requires contrast-enhanced CT when macroscopic hematuria is present or when ≥50 RBCs are present on urinalysis with hypotension or concerning mechanism 1, 2
• Strenuous exercise can cause transient hematuria that resolves with rest 1, 2

Hematologic Causes

• Sickle cell disease causes hematuria through renal papillary necrosis 1, 8
• Coagulopathies (hemophilia, platelet disorders) can manifest with hematuria 1

Rare but Critical Causes

• Wilms tumor is exceedingly rare as a cause of isolated hematuria (occurring in <1% of cases), but any palpable abdominal mass with hematuria requires urgent ultrasound evaluation 1, 2, 4
• Bladder transitional cell carcinoma is extremely rare in children, with only 3 cases identified in one 10-year review of 342 children 7

Age-Specific Patterns

Infants and Toddlers (<3 years)

• Congenital anomalies and urinary tract infections predominate in this age group 7

School-Age Children (3-12 years)

• Post-infectious glomerulonephritis, IgA nephropathy, and hypercalciuria are most common 4, 7

Adolescents (13-20 years)

• Benign urethrorrhagia (19% of males), trauma, and urinary tract infections are frequent causes 7

Critical Diagnostic Distinctions

Glomerular vs. Non-Glomerular Sources

• Glomerular indicators include tea-colored urine, proteinuria (protein-to-creatinine ratio >0.2 g/g), dysmorphic RBCs (>80%), and red blood cell casts 6, 2
• Non-glomerular indicators include bright red blood, absence of significant proteinuria, and normal-appearing RBCs 2, 8

Common Pitfalls to Avoid

• Do not assume isolated microscopic hematuria requires extensive imaging—children without proteinuria or dysmorphic RBCs are unlikely to have clinically significant renal disease and do not need imaging 1, 2
• Do not delay evaluation of gross hematuria—unlike microscopic hematuria, gross hematuria warrants thorough diagnostic evaluation including renal and bladder ultrasound to exclude structural abnormalities 2, 5
• Do not overlook hypercalciuria—this treatable metabolic cause is frequently missed and should be evaluated with spot urine calcium-to-creatinine ratio in all children with persistent hematuria 2, 5
• Do not perform CT scans for isolated microscopic hematuria—CT is not appropriate in the initial evaluation of isolated nonpainful, nontraumatic hematuria without proteinuria in children 1, 2
• Do not ignore family history—screening family members' urine is useful for identifying benign familial hematuria and thin basement membrane nephropathy 1, 2

Benign vs. Serious Disease

• No cause is identified in 34-80% of children with microscopic hematuria after complete evaluation, and these children can be followed clinically without extensive workup 1, 5
• Gross hematuria has no identifiable cause in approximately 38% of cases after thorough evaluation, but the higher yield of clinically important findings (structural abnormalities in 10 patients per 228 cases) justifies comprehensive assessment 7, 5
• Long-term follow-up is mandatory even when no cause is found, as microscopic hematuria can rarely be the first sign of occult progressive renal disease 5, 9