Diagnosing Pediatric Nephritis: Key Tests and Clinical Insights

Accurate diagnosis of nephritis in children requires a comprehensive evaluation by a pediatric nephrologist, combining clinical symptoms with laboratory and imaging studies. Early detection is crucial to prevent complications and ensure effective treatment. Pediatric nephritis often presents with changes in urinary patterns, including reduced urine output (oliguria), altered urine color, visible blood in the urine (gross hematuria), foamy urine indicating protein loss, as well as systemic signs such as edema and hypertension. To confirm the diagnosis and determine the underlying cause, several diagnostic tests are essential.

Essential Diagnostic Tests for Childhood Nephritis

1. Urinalysis: Detecting Early Kidney Damage

Urinalysis is one of the first-line diagnostic tools used to evaluate kidney function and detect abnormalities. It helps identify the presence of hematuria (blood in urine) and proteinuria (excess protein in urine), both of which are hallmark signs of glomerular injury. Dipstick testing provides rapid results, while microscopic examination of urine sediment can reveal red blood cell casts, further supporting a diagnosis of glomerulonephritis.

2. Blood Tests: Assessing Systemic Involvement and Organ Function

Blood work plays a critical role in evaluating the extent of kidney impairment and identifying potential triggers. Key blood tests include:

• Serum creatinine and blood urea nitrogen (BUN) – to assess renal function
• Liver function tests – to rule out hepatic involvement
• Complement levels (especially C3) – low C3 is commonly seen in post-streptococcal glomerulonephritis
• Antistreptolysin O (ASO) titer – to detect recent streptococcal infection, often preceding acute glomerulonephritis
• Erythrocyte sedimentation rate (ESR) – an indicator of inflammation

In many cases of pediatric nephritis, particularly post-streptococcal glomerulonephritis, there is a history of upper respiratory or skin infection caused by group A streptococcus 1–2 weeks prior to symptom onset. Monitoring complement levels over time helps track disease progression and recovery.

3. Blood Pressure and Urine Output Monitoring

During the acute phase of nephritis, close monitoring of blood pressure and daily urine volume is vital. Hypertension is common due to fluid retention and activation of the renin-angiotensin system. Uncontrolled high blood pressure can lead to serious complications such as seizures or acute heart failure. Similarly, tracking urine output helps assess kidney perfusion and detect oliguria or anuria early, allowing timely intervention.

4. Specialized Testing for Secondary Glomerular Diseases

Not all cases of pediatric nephritis are primary. Some are secondary to autoimmune or infectious conditions. Additional targeted testing may be required to rule out these causes:

• ANCA (anti-neutrophil cytoplasmic antibodies) panel – to screen for ANCA-associated vasculitis like granulomatosis with polyangiitis
• Hepatitis B surface antigen (HBsAg) and serology – to exclude hepatitis B virus-related nephropathy
• Antinuclear antibody (ANA) profile and anti-dsDNA – to evaluate for systemic lupus erythematosus (lupus nephritis)

These tests help differentiate between various types of secondary glomerulonephritis and guide long-term management strategies.

5. Renal Biopsy: Defining the Pathological Diagnosis

When the diagnosis remains unclear or the clinical course is atypical, a renal biopsy may be necessary. This procedure involves taking a small sample of kidney tissue for histopathological analysis. It allows physicians to determine the exact type and severity of kidney damage, such as minimal change disease, focal segmental glomerulosclerosis (FSGS), or membranoproliferative glomerulonephritis. Based on the biopsy findings, a tailored treatment plan—including corticosteroids, immunosuppressants, or other targeted therapies—can be implemented.

Early and accurate diagnosis through a combination of clinical assessment and advanced diagnostics significantly improves outcomes in children with nephritis. Parents should seek prompt medical attention if they notice persistent swelling, dark or foamy urine, or unexplained fatigue in their child. With proper care, most children recover fully from acute forms of nephritis, though ongoing follow-up is recommended to monitor kidney health.