What is the likely diagnosis and recommended work‑up and management for a 5‑year‑old presenting with nausea, abdominal pain, and leg swelling?

Likely Diagnosis and Management of a 5-Year-Old with Nausea, Abdominal Pain, and Leg Swelling

Most Likely Diagnosis

The most likely diagnosis is IgA vasculitis (Henoch-Schönlein purpura), which classically presents with abdominal pain and peripheral edema that can precede the characteristic purpuric rash by days to weeks. 1, 2

This diagnosis should be strongly considered even without visible purpura at initial presentation, as approximately 25% of patients do not have the cutaneous rash as their presenting sign 3. The combination of gastrointestinal symptoms and leg swelling in a 5-year-old child falls within the peak incidence age (4-7 years) for this condition 2.

Critical Initial Assessment

Immediate Physical Examination Focus

• Examine all skin surfaces carefully for palpable purpura, particularly on lower extremities, buttocks, and dependent areas—this is the mandatory diagnostic criterion 1, 2
• Assess the character of leg swelling: subcutaneous edema in ankles and feet is common at HSP onset, though can occur in other locations 3
• Evaluate for joint involvement: check for arthritis or arthralgia, present in 75% of cases 1
• Assess hydration status and perfusion: look for signs of hypovolemia (prolonged capillary refill >2 seconds, tachycardia, altered mental status) versus hypervolemia 4
• Blood pressure measurement is essential to evaluate for hypertension suggesting renal involvement 5

Key Historical Elements

• Recent upper respiratory infection (present in most HSP cases) 1, 6
• Fever episodes, character of abdominal pain (diffuse pain occurs in 60-65% of HSP) 1
• Stool characteristics: ask specifically about melena, hematochezia, or occult blood 7
• Urinary symptoms: reduced volume, hematuria, or tea-colored urine 5
• Family history: consanguinity, ethnicity, early infantile deaths, or kidney disease 5
• Prenatal history: if available, ask about enlarged nuchal translucency, increased amniotic fluid alpha-fetoprotein, or large placenta (>25% birth weight), which suggest congenital nephrotic syndrome 5

Diagnostic Work-Up

First-Line Laboratory Evaluation

Obtain the following tests immediately to differentiate between IgA vasculitis and nephrotic syndrome:

• Urinalysis with microscopy: look for hematuria and/or proteinuria (present in 40-50% of HSP; mandatory for nephrotic syndrome diagnosis) 1, 2, 5
• Complete blood count: assess for thrombocytopenia (absent in HSP, may be present in nephrotic syndrome) 1, 5
• Comprehensive metabolic panel: sodium, chloride, ionized calcium, phosphate, magnesium, creatinine, urea, albumin, cholesterol, triglycerides, glucose 5
• Serum albumin level: critical for diagnosing nephrotic syndrome 5
• Serum IgG level: to assess for urinary losses in nephrotic syndrome 5
• Stool guaiac test: positive fecal occult blood significantly increases risk of renal involvement in HSP 7

Additional Testing Based on Initial Results

• If proteinuria is present: calculate protein-to-creatinine ratio; obtain serum cholesterol and triglycerides 5
• If hypoalbuminemia (<2.5 g/dL) with significant proteinuria: consider congenital nephrotic syndrome and proceed with genetic testing 5
• Abdominal ultrasound: evaluate kidney echogenicity and size, assess for ascites, pleural effusions, and thrombosis 5
• Infection screening: if febrile or toxic-appearing, obtain blood cultures; screen for syphilis, toxoplasmosis, CMV, rubella, HBV, HCV, HSV if nephrotic syndrome suspected 5

When to Consider Renal Biopsy

Kidney biopsy is indicated if comprehensive genetic testing and screening for secondary causes are negative, suggesting non-infectious, non-genetic congenital nephrotic syndrome 5. However, biopsy is not routinely needed for HSP diagnosis unless there is severe or progressive renal involvement 1, 2.

Management Algorithm

If IgA Vasculitis (HSP) is Diagnosed

Supportive treatment is the primary intervention, as HSP spontaneously resolves in 94% of children 1:

• For mild abdominal pain and arthralgia: supportive care with adequate hydration and analgesics (avoid NSAIDs if renal involvement present) 1, 2
• For severe abdominal pain or GI hemorrhage: oral prednisone 1-2 mg/kg/day for two weeks reduces mean time to resolution of abdominal symptoms 1, 2
• Monitor for renal involvement: check urinalysis weekly for first month, then monthly for 6 months, as 40-50% develop renal disease 1, 2
• If hematuria/proteinuria develops and persists >3 months: consider ACE inhibitor or ARB to prevent secondary glomerular injury 2
• If severe nephritis develops: early aggressive therapy with high-dose steroids plus immunosuppressants 1

If Congenital Nephrotic Syndrome is Suspected

Rapid referral to a specialized pediatric nephrology unit is essential 5:

• Avoid routine IV fluids and saline; use concentrated oral intake to prevent worsening edema 4
• Administer albumin infusions (1-4 g/kg/day) only for clinical indicators of hypovolemia (prolonged capillary refill, tachycardia, hypotension, oliguria), not based on serum albumin levels alone 4
• Use diuretics with extreme caution and only when intravascular fluid overload is confirmed, as these patients often have intravascular volume depletion despite peripheral edema 4
• Optimize nutrition: provide concentrated high-calorie formulas to meet age-related energy needs while minimizing fluid volume 4
• Restrict dietary sodium to <2 g/day (<90 mmol/day) to maximize diuretic effectiveness if used 4
• Monitor for infections closely: patients have low IgG from urinary losses and are at high risk for bacterial sepsis 5
• Consider IVIG infusions if recurrent/severe infections occur with documented low plasma IgG levels 5

If Acute Gastroenteritis with Dehydration

If vomiting and diarrhea are prominent with signs of dehydration:

• Initiate oral rehydration solution (ORS) using small volumes (5-10 mL every 1-2 minutes) via spoon or syringe 8
• For moderate dehydration (6-9% deficit): administer 100 mL/kg ORS over 2-4 hours 8
• Replace ongoing losses: 10 mL/kg ORS for each watery stool, 2 mL/kg for each vomiting episode 8
• Reserve IV rehydration for severe dehydration (≥10% deficit), shock, altered mental status, or failure of oral rehydration 8
• Rule out urinary tract infection/pyelonephritis given urinary symptoms and abdominal pain 8

Common Pitfalls to Avoid

• Do not dismiss the diagnosis of HSP because purpura is absent—the rash may appear days after GI or joint symptoms begin 3
• Do not assume all leg swelling in children is benign—subcutaneous edema can be an early sign of HSP or nephrotic syndrome 3, 5
• Do not give aggressive IV fluids to a child with nephrotic syndrome—this worsens peripheral edema without improving intravascular volume 4
• Do not use diuretics empirically for edema without confirming intravascular volume status—many nephrotic patients are intravascularly depleted despite appearing edematous 4
• Do not delay renal function monitoring in HSP—renal involvement determines long-term prognosis, and end-stage renal disease occurs in 1-5% of patients 1
• Do not use antimotility agents (loperamide) in children under 18 years if gastroenteritis is suspected 8

Disposition and Follow-Up

• Admit if: severe dehydration, intractable vomiting, severe abdominal pain suggesting intussusception or bowel ischemia, significant renal impairment, or age <3 months 8
• Outpatient management acceptable if: mild symptoms, tolerating oral intake, normal renal function, reliable family for close follow-up 1, 2
• Close renal monitoring required: weekly urinalysis for first month, then monthly for 6 months in all HSP cases 1, 2
• Long-term nephrology follow-up essential if proteinuria or hematuria persists beyond 3 months 2