The triad to remember:
- Microangiopathic haemolytic anaemia
- Thrombocytopenia
- Acute Kidney Injury
Epidemiology: HUS is typically seen in children less than 5 years, and while rates vary with E. coli outbreaks, it is affects about 2-3 per 100,000 children <5 each year
Causes
- The enterohaemorrhagic E. coli O157 verotoxin acquired from undercooked meat or petting farms.
- The verotoxin causes endothelial cell damage and thrombus formation within the renal arteries.
Pathophysiology
Shigella toxin producing E coli (STEC)-related HUS occurs when the bacteria attach to the intestinal cell wall and begin releasing Shiga toxin into circulation.
- Shiga toxin attacks endothelial cells in blood vessels, leading to a bloody diarrhea prodrome.
- In some patients, Shiga toxin triggers platelet activation and the formation of small intravascular thrombi. The formation of these thrombi consumes platelets leading to thrombocytopenia.
- These thrombi begin to obstruct small vessels, such as those in the kidney, leading to acute kidney injury.
- Red blood cells passing through these obstructed blood vessels are sheared by the small thrombi, leading to a microangiopathic hemolysis.
Thus, the toxin produces bloody diarrhea, thrombocytopenia, acute kidney injury and a hemolytic anemia.
PC