Haemolytic uraemic syndrome

Question 1

What is HUS and its cause?

Answer 1

HUS involves thrombosis in small blood vessels throughout the body, usually triggered by shiga toxins from either e.coli or shigella.

Question 2

Who does HUS affect?

Answer 2

HUS most often affects children after an episode of gastroenteritis. Antibiotics and antimotility medications (e.g., loperamide) used to treat gastroenteritis caused by e.coli 0157 or shigella increase the risk of HUS.

Question 3

What does HUS lead to? (triad)

Answer 3

• microangiopathic haemolytic anaemia
• acute kidney injury
• thrombocytopenia (low platelets)

Question 4

Why does HUS lead to these conditions?

Answer 4

• the formation of blood clots consumes platelets, leading to thrombocytopenia
• the blood flow through the kidney is affected by thrombi and damaged RBCs ⇒ AKI
• MAHA involves the destruction of RBCs (haemolysis) due to pathology in the small vessels (microangiopathy)
• tiny blood clots (thrombi) partially obstruct the small blood vessels and churn the red blood cells as they pass through → causing them to rupture

Question 5

What is the presentation of HUS?

Answer 5

• diarrhoea - turns bloody within 3 days & around a week after the onset of diarrhoea, the features of HUS develop:
  
  • fever
  • abdominal pain
  • lethargy
  • pallor
  • oliguria
  • haematuria
  • hypertension
  • bruising
  • jaundice (due to haemolysis)
  • confusion

Question 6

What investigations are done for HUS?

Answer 6

• blood film: schistocytes
• bloods: anaemia: Hb <8 g/dL, thrombocytopenia, U&Es (AKI)
• stool culture is used to establish the causative organism, PCR for Shiga toxins

Question 7

What is the management for HUS?

Answer 7

• HUS is a medical emergency and needs hospital admission and supportive management with treatment of:
  
  • hypovolaemia (eg. IV fluids)
  • hypertension
  • severe anaemia (eg. blood transfusion)
  • severe renal failure (eg. haemodialysis)
• it’s self limiting and patients usually fully recover