Glomerulonephritis refers to inflammation of the glomeruli in the kidneys. The glomerulus is the first part of the nephron. It filters fluid out of the capillaries and into the renal tubule.
Glomerulonephritis describes the pathology that occurs in various diseases rather than being a disease. Treatment is targeted at the underlying cause and often involves supportive care and immunosuppression (e.g., corticosteroids).
Nephritic Syndrome
Nephritis is a very generic term for inflammation in the kidneys. It is a descriptive term and is not a diagnosis.
Nephritic syndrome refers to a group of features that occur with nephritis:
- Haematuria (blood in the urine), which can be microscopic (not visible) or macroscopic (visible)
- Oliguria (significantly reduced urine output)
- Proteinuria (protein in the urine), but less than 3g per 24 hours (higher protein suggests nephrotic syndrome)
- Fluid retention
Nephrotic Syndrome
Nephrotic syndrome occurs when the basement membrane in the glomerulus becomes highly permeable, resulting in significant proteinuria. It refers to a group of features without specifying the underlying cause. It involves:
- Proteinuria (more than 3g per 24 hours)
- Low serum albumin (less than 25g per litre)
- Peripheral oedema
- Hypercholesterolaemia
Nephrotic syndrome presents with oedema. Patients might notice frothy urine due to the high protein content. Nephrotic syndrome predisposes patients to thrombosis, hypertension and high cholesterol.
The most common cause of nephrotic syndrome in children is minimal change disease. This is usually:
- Idiopathic (no identified cause)
- Treated successfully with steroids
The top causes of nephrotic syndrome in adults are:
- Membranous nephropathy
- Focal segmental glomerulosclerosis
Other causes of nephrotic syndrome include:
- Membranoproliferative glomerulonephritis
- Henoch-Schönlein purpura (HSP)
- Diabetes
- Infection (e.g., HIV)
TOM TIP: Minimal change disease comes up fairly frequently in exams as the most common cause of nephrotic syndrome in children. If you spot a 2 – 5 year old child with oedema, proteinuria and low albumin, you may be asked about the underlying cause. The answer is likely to be nephrotic syndrome.
Types of Glomerulonephritis
IgA nephropathy (or Berger’s disease) is the most common cause of primary glomerulonephritis. The exact cause is unclear. The typical patient is in their 20s presenting with haematuria. Histology shows IgA deposits and mesangial proliferation. The mesangial cells are found in the centre of the glomerulus and help support the capillaries (as well as performing other functions).
Membranous nephropathy involves deposits of immune complexes in the glomerular basement membrane, causing thickening and malfunctioning of the membrane and proteinuria. Histology shows IgG and complement deposits on the basement membrane. It is a key cause of nephrotic syndrome in adults. The majority (around 70%) are idiopathic. It can be secondary to malignancy, systemic lupus erythematosus or drugs (e.g. NSAIDs).
Membranoproliferative glomerulonephritis (or mesangiocapillary glomerulonephritis) typically affects patients under 30. It involves immune complex deposits and mesangial proliferation.
Post-streptococcal glomerulonephritis tends to affect patients under 30. It presents 1-3 weeks after a streptococcal infection (e.g., tonsillitis or impetigo). Patients usually make a full recovery.
Rapidly progressive glomerulonephritis (or crescentic glomerulonephritis) presents with an acute severe illness but tends to respond well to treatment. Histology shows glomerular crescents.
Goodpasture syndrome is also known as anti-glomerular basement membrane (anti-GBM) disease. Anti-GBM (glomerular basement membrane) antibodies attack the glomerulus and pulmonary basement membranes. It causes glomerulonephritis and pulmonary haemorrhage. The typical presentation is a patient in their 20s or 60s with acute kidney failure and haemoptysis (coughing up blood).
Systemic diseases that can cause glomerulonephritis include:
- Henoch-Schönlein purpura (HSP)
- Vasculitis (e.g., microscopic polyangiitis or granulomatosis with polyangiitis)
- Lupus nephritis (associated with systemic lupus erythematosus)
TOM TIP: If you come across a patient in your exams with significant acute kidney injury and haemoptysis, the top conditions to consider can be differentiated based on the antibodies:
- Anti-GBM antibodies – Goodpasture syndrome
- p-ANCA (or MPO antibodies) – microscopic polyangiitis
- c-ANCA (or PR3 antibodies) – granulomatosis with polyangiitis
Management
Diagnosis may require a renal biopsy for histology.
A renal specialist will guide treatment, which depends on the underlying cause. It may involve:
- Supportive care (e.g., hypertension management and dialysis in severe disease)
- Immunosuppression (e.g., corticosteroids)
Last updated September 2023