Nephrotic Syndrome in Children
Nephrotic syndrome is a common renal disease in children, characterised by a triad of significant proteinuria, hypoalbuminaemia, and oedema. It’s more prevalent in preschool and school-aged children, and the most common cause is minimal change disease, which responds well to steroids.
Pathophysiology
Nephrotic syndrome results from an increased permeability of the glomerular basement membrane in the kidneys, which allows large proteins, particularly albumin, to leak into the urine. The loss of albumin leads to hypoalbuminaemia, which in turn causes a reduction in plasma oncotic pressure, leading to fluid shifting from the intravascular space into the interstitial space and causing oedema.
Clinical Presentation
Oedema: This is the cardinal sign. It is typically pitting and often starts around the eyes (periorbital) before progressing to the legs, feet, and scrotum. Severe cases can lead to ascites (fluid in the abdomen) and pleural effusions (fluid around the lungs).
Other symptoms: Children may have a reduced urine output and may present with lethargy and abdominal pain.
Investigations
Urine Analysis:
A urine dipstick will show significant proteinuria (3+ or more).
A spot urine albumin:creatinine ratio of >200 mg/mmol confirms significant proteinuria.
Bloods:
Low serum albumin ( g/L).
Elevated cholesterol and triglycerides due to the liver’s compensatory increase in protein and lipid production.
Normal complement levels (C3 and C4) are a key finding in minimal change disease. Low C3 may suggest another cause, such as post-streptococcal glomerulonephritis.
Raised haematocrit suggests intravascular hypovolaemia.
Management
Management is a balance between supportive care, treating the underlying disease, and managing complications.
Supportive Care:
Admission: All children with a new diagnosis should be admitted for a period of observation and to confirm the diagnosis.
Fluid and Salt Restriction: Restrict fluid intake to 800-1000 ml per day and avoid excess salt.
Corticosteroids:
High-dose oral prednisolone is the first-line treatment for minimal change disease. The usual UK regimen is 60 mg/m² per day for 4 weeks, followed by a slower taper.
Complications:
Infection: The low IgG levels in nephrotic syndrome increase the risk of infection, especially spontaneous bacterial peritonitis. Prophylactic penicillin V may be used while the child has significant oedema.
Thrombosis: The hypercoagulable state puts children at a risk of thrombosis, particularly in the renal veins or cerebral venous sinuses.
Intravascular Hypovolaemia: In severe oedema, there is a risk of intravascular hypovolaemia. If suspected, a fluid challenge with 20% albumin may be needed to draw fluid from the interstitial space back into the circulation, followed by a diuretic like furosemide.
Prognosis
The prognosis is generally good, with most children having steroid-sensitive nephrotic syndrome. A relapse is defined as proteinuria of 3+ on three consecutive mornings, at which point the steroid regimen is restarted. Children who do not respond to steroids after 4 weeks of treatment are considered steroid-resistant and require a referral for a renal biopsy to identify the cause and guide further management.