Nephritic Syndrome

Overview – Nephritic Syndrome

Nephritic syndrome is a constellation of clinical findings that arise from inflammatory damage to the glomeruli, resulting in red blood cell leakage into the urine and decreased glomerular filtration. It is most often associated with autoimmune or post-infectious processes and is a key cause of acute kidney injury (AKI), especially in children and young adults. Recognising the classical signs—haematuria, oliguria, hypertension, and oedema—is crucial for early diagnosis and targeted treatment. This overview sets the stage before exploring specific nephritic conditions in more detail.

Definition

Nephritic syndrome refers to a group of disorders characterised by:

• Glomerular inflammation and damage, leading to:
  • ↓ Glomerular Filtration Rate (GFR)
  • RBCs leaking into urine → Haematuria
  • Mild to moderate proteinuria (usually <3.5 g/day)
  • Oliguria (low urine output)
  • Hypertension (from fluid retention and activation of RAAS)
  • Azotaemia and elevated serum creatinine

Clinical Features

• Acute kidney injury (AKI) → ↓GFR
• Oliguria
  • → Renal hypertension (via JG cell hypoperfusion)
  • → Fluid overload → oedema
• Haematuria (++++)
  • → RBC (cellular) casts in urine
  • → Anaemia
• Microalbuminuria
• Elevated urea and creatinine
• Note: Patients are fluid overloaded due to oliguria and oedematous due to that overload

Investigations

• Urinalysis:
  • RBC casts
  • Haematuria
  • Mild proteinuria
• Bloods:
  • ↑ Creatinine
  • ↑ Urea
  • ↓ Haemoglobin (anaemia)
• Serologies:
  • ANA, anti-dsDNA, ANCA, anti-GBM (if autoimmune suspected)
• Renal biopsy:
  • Definitive diagnosis, shows glomerular inflammation and potential crescent formation

Management

• Diuretics (e.g. frusemide): Reduce fluid overload
• ACE inhibitors: Manage hypertension and reduce intraglomerular pressure
• Fluid restriction: If overloaded
• Dietary control:
  • Low sodium
  • Low potassium
• Immunosuppressive therapy: If autoimmune cause (covered in disease-specific pages)
• Dialysis: If severe or unresponsive AKI

Complications

• Progression to chronic kidney disease (CKD)
• Hypertensive crisis
• Volume overload complications: Pulmonary oedema, pleural effusions
• End-stage renal failure (if untreated or rapidly progressive)

Causes of Nephritic Syndrome

Nephritic syndrome may be triggered by a variety of immune and infectious processes. It is not a single disease but rather a pattern of injury.

Common Causes:

• Post-Streptococcal Glomerulonephritis (PSGN) – classically post-infectious in children
• IgA Nephropathy (Berger’s Disease) – most common adult cause
• Lupus Nephritis – due to SLE
• Hemolytic-Uremic Syndrome (HUS) – often in children post-E. coli infection
• Rapidly Progressive Glomerulonephritis (RPGN) – any severe glomerulonephritis can evolve into RPGN
• Anti-GBM disease (Goodpasture’s syndrome)
• ANCA-associated vasculitis (e.g. Wegener’s, Microscopic Polyangiitis)

Each cause is covered in its own dedicated article. Visit the disease-specific pages linked from this overview.

Summary – Nephritic Syndrome

Nephritic syndrome is a glomerular disease pattern defined by haematuria, oliguria, hypertension, and often AKI, resulting from inflammation-driven damage to the kidney’s filtration system. It is crucial for clinicians to distinguish it from nephrotic syndromes, as the underlying causes and treatments differ significantly. For more renal topics, visit our Renal Overview page.