Residency · Residency · Medicine-Pediatrics

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

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.

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.

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

1. Ingelfinger JR, Davis AE, Bhatt K. Evaluation of hematuria in children. N Engl J Med. 2021;385(27):2559-2565.
2. Barocas DA, Boorjian SA, Alvarez RD, et al. Microhematuria: AUA/SUFU guideline. J Urol. 2020;204(4):778-786.
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.

For the intern

At 3am, confirm true hematuria with urinalysis microscopy and urine culture. If the patient is unstable with AKI, oliguria, or hypertensive emergency, call your senior immediately for possible acute glomerulonephritis or rapidly progressive disease. Check basic labs (CBC, BMP, albumin) and obtain renal ultrasound if available. Stable patients with isolated microscopic hematuria can have outpatient workup arranged in the morning—this includes cystoscopy referral for adults over 35 and nephrology referral for suspected glomerular disease (proteinuria, RBC casts, dysmorphic RBCs). For gross hematuria with clots, ensure adequate hydration and monitor for urinary retention. Don't forget to exclude non-hematuria red urine causes (medications, foods, menses).

Common pitfalls

• Accepting dipstick alone: Positive dipstick without RBCs on microscopy means hemoglobinuria (hemolysis) or myoglobinuria (rhabdomyolysis), not hematuria. Always confirm with microscopy.
• Missing cancer in anticoagulated patients: "The warfarin made them bleed" is dangerous thinking. Anticoagulation unmasks underlying pathology—all patients require full anatomic evaluation regardless of INR.
• Age-inappropriate workup: Don't order cystoscopy on a 6-year-old with post-strep glomerulonephritis, and don't skip malignancy evaluation in a 50-year-old smoker just because C3 is slightly low.
• Ignoring RBC casts: These are pathognomonic for glomerulonephritis and demand immediate nephrology involvement, especially with rising creatinine.

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