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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
Key points
- Minimal change disease is the most common cause of nephrotic syndrome in children
- Classic features: periorbital/dependent edema, nephrotic-range proteinuria, hypoalbuminemia, and hyperlipidemia
- Urinalysis shows heavy protein with bland sediment; gross hematuria, hypertension, low complement, or renal dysfunction suggests another diagnosis
- Most children respond to corticosteroids; steroid resistance requires nephrology evaluation and often kidney biopsy
- Complications include infection, thrombosis, hypovolemia/AKI, and relapse
Overview
Childhood nephrotic syndrome is a glomerular permeability disorder causing massive urinary protein loss. In children, minimal change disease is the classic and most common cause and usually responds to corticosteroids. The key exam distinction is nephrotic syndrome (edema and heavy proteinuria) versus nephritic syndrome (hematuria, hypertension, reduced kidney function, RBC casts).
Epidemiology
Minimal change disease typically presents between ages 2 and 6 years and is more common in boys. It may follow viral infection, immunization, or allergic trigger. Most children achieve remission with steroids, but relapses are common.
Clinical Features
Symptoms
Periorbital swelling, especially in morning
Dependent edema, abdominal distension, scrotal/labial edema
Frothy urine or decreased urine output
Fever, abdominal pain, or spontaneous bacterial peritonitis symptoms
Dyspnea or unilateral limb swelling suggesting effusion or thrombosis
Signs
Pitting edema and ascites
Normal or mildly elevated blood pressure in typical minimal change disease
No gross hematuria or systemic rash in typical disease
Hypovolemia: tachycardia, abdominal pain, delayed capillary refill despite edema
Hypertension, gross hematuria, low complement, or renal impairment are atypical red flags
Investigations
First-line
Urinalysis and urine protein/creatinine ratioHeavy proteinuria with bland sediment; quantify protein loss
Serum albumin and lipid panelHypoalbuminemia and hyperlipidemia support nephrotic syndrome
BMP/creatinine and electrolytesAssess kidney function and complications
Second-line
Complement C3/C4, ANA, hepatitis testingIf atypical features suggest nephritic/systemic disease
Renal ultrasoundSelected cases with atypical presentation or renal dysfunction
Tuberculosis/varicella statusImportant before prolonged corticosteroid therapy in selected patients
Specialist
Pediatric nephrologyAge <1 or >12 years, steroid resistance, frequent relapses, gross hematuria, hypertension, low complement, renal dysfunction, or systemic features
Kidney biopsyUsually not needed for typical steroid-sensitive minimal change disease; indicated for atypical or steroid-resistant cases
1
Initial management
- Salt restriction and edema management; diuretics cautiously if significant edema and intravascular volume adequate
- Corticosteroids are first-line for typical minimal change nephrotic syndrome
- Vaccination review and infection precautions; avoid live vaccines during high-dose immunosuppression
2
Monitoring response
- Track urine protein at home with dipsticks when instructed
- Remission usually occurs with steroid therapy in minimal change disease
- Relapse is recurrence of proteinuria after remission and is common
3
Complication management
- Evaluate fever/abdominal pain promptly for peritonitis or sepsis
- Consider thrombosis with unilateral swelling, respiratory symptoms, severe hypoalbuminemia, or hematuria/flank pain
- Albumin plus diuretic may be used in severe edema/hypovolemia under specialist care
Complications
- Infection: Loss of immunoglobulins and complement factors increases risk, including spontaneous bacterial peritonitis
- Thrombosis: Urinary loss of antithrombin III and hemoconcentration increase risk
- Hypovolemia and AKI: Edema can coexist with low effective circulating volume
- Relapse and steroid toxicity: Growth effects, hypertension, hyperglycemia, mood changes, and infection risk
- Alternative glomerular disease: Steroid resistance may reflect FSGS or another pathology
USMLE Step 2 CK Exam Tips
- 1Child with periorbital edema + 3-4+ proteinuria = nephrotic syndrome
- 2Minimal change disease is the most common pediatric nephrotic syndrome
- 3Heavy proteinuria, hypoalbuminemia, hyperlipidemia, edema = nephrotic
- 4Hematuria, hypertension, RBC casts, low complement = not typical minimal change; think nephritic process
- 5Most children respond to steroids, so biopsy is not first step in classic presentation
- 6Fever and abdominal pain in nephrotic syndrome = spontaneous bacterial peritonitis until proven otherwise
- 7Thrombosis risk is increased from urinary antithrombin loss
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