What are the possible causes of hematuria on urinalysis in a 13‑year‑old female?

Possible Causes of Hematuria in a 13-Year-Old Female

In a 13-year-old female with blood on urinalysis, the most likely causes are urinary tract infection, glomerulonephritis (especially post-infectious or IgA nephropathy), hypercalciuria, exercise-induced hematuria, or menstrual contamination—while malignancy is exceedingly rare in this age group. 1

Most Common Etiologies in Adolescent Females

Infectious Causes

• Urinary tract infection is the leading cause of both microscopic and macroscopic hematuria in children and adolescents, identified by leukocytes and microorganisms on urinalysis 1
• If infection is suspected, obtain urine culture before antibiotics and treat appropriately; if hematuria resolves after infection treatment, no additional evaluation is necessary 2

Glomerular/Renal Causes

• Post-infectious glomerulonephritis commonly follows streptococcal throat or skin infections by 1-3 weeks and presents with tea-colored urine, proteinuria, and sometimes hypertension 1
• IgA nephropathy (Berger disease) is the most common glomerular disorder in children, typically presenting with recurrent gross hematuria following upper respiratory infections and requiring renal biopsy for definitive diagnosis 1
• Alport syndrome should be considered if there is family history of kidney disease or hearing loss; work-up includes audiometry and slit-lamp examination 1
• Thin basement membrane nephropathy is the most common cause of benign familial hematuria; screening urine from family members aids diagnosis 1

Metabolic Causes

• Hypercalciuria is a frequent cause of microscopic hematuria in children and may predispose to nephrolithiasis; evaluate with spot urine calcium-to-creatinine ratio 1
• Hyperuricosuria can produce microscopic hematuria and increase nephrolithiasis risk 1

Urologic/Structural Causes

• Urolithiasis accounts for approximately 5% of pediatric hematuria cases 1
• Congenital renal anomalies occur in 1-4% of the population and may present with hematuria, especially after minor trauma 1

Benign/Transient Causes

• Menstrual contamination is a common cause of false-positive hematuria in adolescent females; obtain a catheterized specimen if clean-catch is unreliable 2
• Strenuous exercise can cause transient, self-limited hematuria that resolves with rest 1
• Viral illness may be associated with transient microscopic hematuria that resolves after the illness 3

Systemic/Hematologic Causes

• Henoch-Schönlein purpura presents with hematuria accompanied by palpable purpuric rash, arthritis, and peripheral edema 1
• Sickle cell disease may cause hematuria through renal papillary necrosis 1
• Coagulopathies (hemophilia, platelet disorders) can manifest as hematuria 1

Rare but Serious Causes

• Wilms tumor is an extremely rare cause of isolated hematuria (<1%); any child with a palpable abdominal mass plus hematuria requires urgent renal ultrasound 1
• Bladder or renal malignancy is exceedingly rare in children compared to adults 1

Critical Diagnostic Approach

Initial Urinalysis Interpretation

• Confirm true hematuria with microscopic examination showing ≥3 red blood cells per high-power field on a properly collected clean-catch specimen 2
• Differentiate glomerular from non-glomerular sources by examining for dysmorphic RBCs (>80% suggests glomerular), red cell casts (pathognomonic for glomerulonephritis), and degree of proteinuria 1
• Tea-colored or cola-colored urine with proteinuria strongly suggests glomerular disease 1

When Imaging Is NOT Needed

• Isolated microscopic hematuria in an otherwise well child without proteinuria or dysmorphic RBCs requires no imaging, as clinically significant renal disease is unlikely 1
• A large study of 325 pediatric patients with microscopic hematuria found no clinically significant findings on imaging, supporting conservative management 1

When Imaging IS Indicated

• Gross (visible) hematuria warrants renal and bladder ultrasound to evaluate for structural abnormalities, stones, or rarely tumors 1
• Painful hematuria suspected to be urolithiasis should be evaluated with ultrasound first-line, though CT may be needed if ultrasound is negative and clinical suspicion remains high 1
• Hematuria with palpable abdominal mass requires urgent ultrasound to evaluate for Wilms tumor or other renal masses 1
• Traumatic hematuria (macroscopic or ≥50 RBCs/HPF with hypotension or concerning mechanism) necessitates contrast-enhanced CT of abdomen and pelvis 1

Key Clinical Pitfalls to Avoid

• Do not order advanced imaging (CT, MRI, VCUG) for isolated, transient microscopic hematuria in an otherwise well child—this exposes the patient to unnecessary radiation and risk without diagnostic benefit 1
• Do not assume menstrual contamination without obtaining a properly collected specimen; if clean-catch is unreliable, obtain catheterized urine 2
• Do not dismiss family history—screening urine of relatives helps identify benign familial hematuria and thin basement membrane nephropathy 1
• Do not delay evaluation if concerning features develop, including proteinuria, tea-colored urine, red cell casts, hypertension, or systemic symptoms 1
• Remember that 34-80% of children with microscopic hematuria have no identifiable cause after complete work-up and can be managed with clinical observation 1