What is the best management approach for a 5-year-old female patient presenting with impaired renal function, electrolyte imbalance, hypotension, tachycardia, tachypnea, and abnormal urinalysis?

Management of Acute Kidney Injury with Severe Electrolyte Disturbances in a 5-Year-Old

This child requires immediate hospitalization with urgent nephrology consultation and aggressive supportive care for acute kidney injury with severe hyponatremia, hypovolemic shock, and likely nephrotic syndrome. 1, 2

Immediate eGFR Calculation and Interpretation

Using the Schwartz formula for pediatric eGFR: eGFR = (k × height in cm) / serum creatinine (mg/dL), where k = 0.413 for children aged 1-12 years 3

• Converting creatinine: 401.45 μmol/L = 4.54 mg/dL
• Assuming average height for 5-year-old female (~110 cm): eGFR ≈ 10 mL/min/1.73m² 3
• This represents severe kidney dysfunction (KDIGO stage G5) 1
• The BUN/Cr ratio of 74 mmol/L ÷ 4.54 mg/dL = 16.3, which is within normal range, suggesting intrinsic renal disease rather than prerenal azotemia 4, 5

Critical Initial Assessment and Stabilization

The combination of hypotension (93/33 mmHg), tachycardia (168/min), tachypnea (45/min), and severe hyponatremia (121.8 mmol/L) indicates hypovolemic shock requiring immediate intervention 1, 2

Volume Status Assessment

• Clinical indicators of hypovolemia are present: hypotension, tachycardia, and likely oliguria given the severe AKI 1, 2
• The 3+ proteinuria with specific gravity 1.010 suggests nephrotic-range proteinuria with loss of concentrating ability 1, 6
• Administer 20% albumin infusion (0.5-1 g/kg over 2-4 hours) followed by furosemide (1-2 mg/kg IV) at the end of infusion to enhance diuresis and restore intravascular volume 1, 2

Severe Hyponatremia Management

• The sodium of 121.8 mmol/L with neurological risk (tachypnea may indicate compensatory response) requires cautious correction 1
• Correct sodium at maximum 10-12 mmol/L per 24 hours to avoid osmotic demyelination syndrome 1
• Use 3% hypertonic saline only if symptomatic (seizures, altered mental status), otherwise correct with albumin infusion and fluid restriction 1

Diagnostic Workup

The urinalysis showing turbid, dark urine with 3+ protein strongly suggests nephrotic syndrome, though the presentation includes nephritic features 1, 2, 6

Essential Laboratory Studies

• Spot urine protein-to-creatinine ratio to quantify proteinuria (likely >2 g/g given 3+ dipstick) 1, 2
• Serum albumin, total protein, lipid panel to confirm nephrotic syndrome 1, 2
• Complete blood count with differential, inflammatory markers (ESR, CRP) 1
• Complement levels (C3, C4), ANA, anti-dsDNA, ANCA panel to evaluate for secondary causes 6
• Hepatitis B, C, HIV screening given the proteinuria 1
• Urine microscopy for RBC casts (suggests nephritic component) 6

Imaging

• Renal ultrasound with Doppler to assess kidney size, echogenicity, rule out obstruction, and evaluate for renal vein thrombosis (complication of nephrotic syndrome) 1

Ongoing Management Strategy

Fluid and Electrolyte Management

• Strict fluid restriction to insensible losses plus urine output (approximately 400-600 mL/m²/day) 1, 2
• Avoid intravenous saline; concentrate oral fluids 1
• Monitor serum electrolytes every 6-12 hours initially, then daily once stable 1
• Potassium is currently normal (3.67 mmol/L) but requires close monitoring as it may rise with worsening AKI 1

Diuretic Therapy

• After volume resuscitation with albumin, initiate furosemide 1-2 mg/kg IV every 6-12 hours 1
• If inadequate response, consider sequential nephron blockade with addition of metolazone 0.1-0.2 mg/kg/dose once daily 1
• Monitor for hypokalemia with aggressive diuresis, though current potassium is acceptable 1

Blood Pressure Management

• Current BP (93/33 mmHg) is hypotensive for age; once euvolemia achieved, reassess for hypertension typical of nephritic syndrome 6
• If hypertension develops after volume restoration, initiate ACE inhibitor (enalapril 0.08 mg/kg/day) for both BP control and antiproteinuric effect 1

Renal Replacement Therapy Considerations

• With eGFR ~10 mL/min/1.73m² and clinical instability, prepare for potential dialysis if: 1
  • Severe hyperkalemia develops (>6.5 mmol/L)
  • Refractory fluid overload with pulmonary edema
  • Symptomatic uremia (pericarditis, encephalopathy)
  • Inability to correct severe hyponatremia safely
  • Severe metabolic acidosis (pH <7.1)

Nephrology Consultation and Definitive Diagnosis

Urgent pediatric nephrology consultation is mandatory given the severity of presentation and need for potential kidney biopsy 1, 2

Biopsy Considerations

• Kidney biopsy should be strongly considered once hemodynamically stable and coagulation parameters acceptable to determine underlying etiology 1, 2
• The combination of severe proteinuria, AKI, and young age raises concern for congenital nephrotic syndrome, focal segmental glomerulosclerosis, or minimal change disease with acute tubular necrosis 1, 2
• Biopsy is particularly important given the severity and to guide immunosuppressive therapy decisions 2

Genetic Testing

• Send genetic panel for congenital nephrotic syndrome genes (NPHS1, NPHS2, WT1, LAMB2) given age and severity 1

Infection Prophylaxis and Complications

Children with nephrotic syndrome and severe hypoalbuminemia are at high risk for bacterial infections, particularly spontaneous bacterial peritonitis and sepsis 1

• Consider prophylactic antibiotics if albumin <2 g/dL and peritoneal signs develop 1
• Avoid central venous lines if possible due to thrombosis risk; if required, provide prophylactic anticoagulation 1
• Monitor for signs of infection at every clinical contact 1

Monitoring Parameters

Given KDIGO stage G5 CKD, laboratory monitoring should occur every 1-3 months once stabilized 1

• Serum electrolytes, BUN, creatinine 1
• Acid-base status (venous blood gas or total CO₂) 1
• Calcium, phosphate, PTH, 25-OH vitamin D 1
• Hemoglobin and iron studies 1
• Spot urine protein-to-creatinine ratio 1, 2

Critical Pitfalls to Avoid

• Do not rely on serum creatinine alone in children; always calculate eGFR using age-appropriate formulas 3, 4
• Do not administer albumin based solely on low levels; only give for clinical hypovolemia 1, 2
• Do not correct severe hyponatremia too rapidly (>10-12 mmol/L per 24 hours) 1
• Do not assume nephrotic syndrome alone; the severe AKI and mixed picture require biopsy for definitive diagnosis 1, 2, 6
• Do not delay nephrology referral; this child requires subspecialty management immediately 1, 2