The terminology around intrinsic kidney diseases gets very confusing, so it is really important to thoroughly understand the fundamentals or you risk getting very confused later.
Nephritis is a very generic term that means inflammation of the kidneys. It is a very non-specific descriptive term and is not a diagnosis or syndrome that has any criteria. It is easy to get confused and think that when a patient is described as having “nephritis” this is a diagnosis. It is not, they are simply saying that the patient has inflammation of the kidney.
Nephritic syndrome or acute nephritic syndrome refers to a group of symptoms, not a diagnosis. When we say a patient has “nephritic syndrome” it simply means they fit a clinical picture of having inflammation of their kidney and it does not represent a specific diagnosis or give the underlying cause. Unlike nephrotic syndrome, there are no set criteria. However, there are the following features in nephritic syndrome:
- Haematuria means blood in the urine. This can be microscopic (not visible) or macroscopic (visible).
- Oliguria means there is a significantly reduced urine output.
- Proteinuria is protein in the urine. In nephritic syndrome, there is less than 3g / 24 hours. Any more and it starts being classified as nephrotic syndrome.
- Fluid retention
Nephrotic syndrome refers to a group of symptoms without specifying the underlying cause. Therefore, nephrotic syndrome is not a disease, but is a way of saying “the patient has these symptoms”, which indicates there is an underlying disease present but doesn’t specify the disease. To have nephrotic syndrome a patient must fulfil the following criteria:
- Peripheral oedema
- Proteinuria more than 3g / 24 hours
- Serum albumin less than 25g / L
Glomerulonephritis is an umbrella term applied to conditions that cause inflammation of or around the glomerulus and nephron. There are many conditions that can be described as glomerulonephritis. Below there is a list of the types of glomerulonephritis. These are specific diseases and diagnoses that have their own pathophysiology.
Interstitial nephritis is a term to describe a situation where there is inflammation of the space between cells and tubules (the interstitium) within the kidney. It is important not to confuse this with glomerulonephritis. Under the umbrella term of interstitial nephritis, there are two key specific diagnoses: acute interstitial nephritis and chronic tubulointerstitial nephritis. These are discussed in a later section.
Glomerulosclerosis is a term to describe the pathological process of scarring of the tissue in the glomerulus. It is not a diagnosis in itself and is more a term used to describe the damage and scarring done by other diagnoses. Glomerulosclerosis can be caused by any type of glomerulonephritis or obstructive uropathy (blockage of urine outflow), and by a specific disease called focal segmental glomerulosclerosis.
Specific Types of Glomerulonephritis
Each disease listed has its own epidemiology, causes and treatments. It is easy to get overwhelmed and confused since they are very similar names. I would suggest not trying to learn every detail until you really understand the basics. If you understand the basics you will be ahead of most of your colleagues.
- Minimal change disease
- Focal segmental glomerulosclerosis
- Membranous glomerulonephritis
- IgA nephropathy (AKA mesangioproliferative glomerulonephritis or Berger’s disease)
- Post streptococcal glomerulonephritis (AKA diffuse proliferative glomerulonephritis)
- Mesangiocapillary glomerulonephritis
- Rapidly progressive glomerulonephritis
- Goodpasture Syndrome
Here are some key facts that will allow you to answer almost all exam questions on glomerulonephritis without getting overwhelmed and confused trying to learn everything about kidneys.
Most types of glomerulonephritis are treated with:
- Immunosuppression (e.g. steroids)
- Blood pressure control by blocking the renin-angiotensin system (i.e. ACE inhibitors or angiotensin-II receptor blockers)
Nephrotic syndrome usually presents with oedema. Patients might notice frothy urine (proteinuria). 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 most common cause of nephrotic syndrome in adults is focal segmental glomerulosclerosis.
IgA nephropathy (AKA Berger’s disease)
IgA nephropathy is the most common cause of primary glomerulonephritis (not caused by another disease). The peak age at presentation is in the 20s. Histology shows “IgA deposits and glomerular mesangial proliferation”.
- Most common type of glomerulonephritis overall
- There is a bimodal peak in age in the 20s and 60s
- Histology shows “IgG and complement deposits on the basement membrane”
- The majority (~70%) are idiopathic
- Can be secondary to malignancy, rheumatoid disorders and drugs (e.g. NSAIDS)
Post streptococcal glomerulonephritis (AKA diffuse proliferative glomerulonephritis)
Patients are typically under 30 years. It presents as:
- 1-3 weeks after a streptococcal infection (e.g. tonsillitis or impetigo)
- They develop a nephritic syndrome
- There is usually a full recovery
Anti-GBM (glomerular basement membrane) antibodies attack glomerulus and pulmonary basement membranes. This causes glomerulonephritis and pulmonary haemorrhage. In your exam, there may be a patient that presents with acute kidney failure and haemoptysis (coughing up blood).
TOM TIP: If you come across a patient in your exam with the combination of acute renal failure and haemoptysis, think of two conditions: Goodpasture syndrome and granulomatosis with polyangiitis (AKA Wegener’s granulomatosis). Goodpasture syndrome is associated with anti-GBM antibodies, whereas Wegener’s granulomatosis is a type of vasculitis associated with anti-neutrophil cytoplasmic antibodies (ANCA). Patients with Wegener’s granulomatosis may also have a wheeze, sinusitis and a saddle-shaped nose.
Rapidly progressive glomerulonephritis
- Histology shows “crescentic glomerulonephritis”
- It presents with a very acute illness with sick patients but it responds well to treatment
- Often secondary to Goodpasture syndrome
Last updated April 2019