Definitions

• Nephritis essentially means inflammation of the kidney. Nephritis may involve the glomerulus, tubule, or the interstitial renal tissue.
• When inflammation involves the glomeruli it is called glomerulonephritis.
• When kidney disease involves structures in the kidney outside the glomerulus, it is broadly referred to as tubulointerstitial disease. This disease generally involves the tubules and/or the interstitium of the kidney and spares the glomeruli.
• When inflammation affects the area of the kidney between the nephrons (the renal interstitium) it is known as interstitial nephritis, or sometimes tubulo-interstitial nephritis.¹
• Nephrosis is a descriptive histopathological term for renal disease without an inflammatory component.

Renal disease can present in a number of different ways, including as:

• Nephritic syndrome (nephritis)
• Nephrotic syndrome (nephrosis)
• Acute renal failure
• Chronic renal failure
• Hypertension
• Renal pain and dysuria

• Nephrotic Syndrome
• Acute Renal Failure
• Chronic Kidney Disease
• Renal Tubular Disease
• Goodpasture's syndrome
• IgA Nephropathy (Berger's Disease)

Acute nephritic syndrome

Acute nephritic syndrome is the most serious and potentially devastating form of the various renal syndromes.²

Clinical features

The key clinical features of acute nephritic syndrome are:

• Haematuria
• Reduced urine output
• Fluid retention and oedema (including periorbital, pedal and pulmonary oedema)
• Proteinuria
• Hypertension
• Uraemic symptoms (including anorexia, pruritus, lethargy, nausea)
• Deteriorating renal function

Causes²

• Post-infection with nephritogenic strains of group A beta-haemolytic streptococcus (typically occurs in children)
• Any of the other causes of glomerulonephritis
  • Other bacterial infections - e.g. typhoid, secondary syphilis, MRSA infection, pneumococcal pneumonia, infective endocarditis
  • Viral infections - e.g. hepatitis B, mumps, measles, infectious mononucleosis, varicella, coxsackievirus
  • Parasitic infections - e.g. malaria, toxoplasmosis
  • Multisystem systemic diseases - e.g. systemic lupus erythematosus, vasculitis, Henoch-Schönlein purpura, Goodpasture syndrome, Wegener granulomatosis
  • Primary glomerular diseases - e.g. Berger disease (IgA nephropathy), membranoproliferative glomerulonephritis
  • Guillain-Barré syndrome
  • Diphtheria-pertussis-tetanus vaccine

Management

In primary care:

• Take a history - ask about onset of symptoms, uraemic symptoms, look for a clue to underlying cause e.g. recent streptococcal infection, other infection, multisystem disease.
• Measure blood pressure.
• Assess for peripheral, periorbital and pulmonary oedema.
• Perform urine dipstick for protein and blood.
• If acute nephritic syndrome is suspected, patients should be referred to secondary care. Acute admission may be required.

In secondary care:

• Investigations are focused on assessing severity of renal injury and looking for the underlying cause. They are discussed in detail in the article entitled Glomerulonephritis.
• Management depends on the underlying cause and is also discussed in the same article.

Prognosis

• This depends on the underlying cause.
• Nephritic syndrome caused by acute post-streptococcal glomerulonephritis in children is generally excellent.²

Nephrotic syndrome

Clinical features

The key clinical features of nephrotic syndrome are:

• Proteinuria (formerly defined as >3.5 g/day but there appears to be individual variation around this cut-off figure)
• Hypoalbuminaemia as a result of urinary protein loss (albumin levels usually in range <25–30 g/l)
• Peripheral oedema due to hypoalbuminaemia
• Hypercholesterolaemia/dyslipidaemia

Causes

• Primary renal diseases
  • Minimal-change nephrotic syndrome (~85% of childhood cases)
  • Focal segmental glomerulosclerosis (~9% of childhood cases)
  • Mesangial proliferative glomerulonephritis (~2% of childhood cases)
  • Membranous nephropathy (~3% of childhood cases)
  • Membranoproliferative glomerulonephritis
• Secondary renal diseases
  • Postinfectious causes, e.g. Group-A beta-haemolytic streptococci, TB, malaria, syphilis, viruses such as VZV, HBV, HIV, infectious mononucleosis
  • Collagen vascular diseases, e.g. SLE, rheumatoid arthritis, polyarteritis nodosa, Henoch-Schönlein purpura, vasculitides
  • Metabolic diseases, e.g. diabetes mellitus, amyloidosis
  • Inherited disease, e.g. Alport's syndrome, hereditary nephritis, sickle cell disease
  • Malignant disease, e.g. multiple myeloma, leukaemia, lymphoma, carcinoma of breast/lung/colon/stomach
  • Medications, e.g. NSAIDs, captopril, lithium, gold, diamorphine, interferon-alpha, penicillamine, probenecid and many others
  • Toxins, e.g. bee sting, snake bites, phytotoxins
  • Pregnancy, e.g. pre-eclampsia
  • Transplant rejection

Management

In primary care:

• Take a history - onset of symptoms may be gradual over a few weeks, look for a clue to underlying cause, some patients describe their urine as frothy, there may be associated lethargy and anorexia.
• Measure blood pressure (although hypertension is not usually found).
• Assess for peripheral, periorbital and pulmonary oedema and ascites.
• Look for deep vein thrombosis can occur due to a hypercoagulable state.³
• Perform urinalysis which will show gross proteinuria.
• If nephrotic syndrome is suspected, patients should be referred to secondary care. However, most do not require acute admission.
• The separate article on Nephrotic Syndrome (click here) discusses investigations and management in more detail.

Document references

1. Alper Jr AB; Nephritis, Interstitial, eMedicine, Nov 2009
2. Parmar MS; Acute Glomerulonephritis. eMedicine, July 2008.
3. Cohen EP; Nephrotic Syndrome, eMedicine, Mar 2010

Acknowledgements