Haemolytic uraemic syndrome

Question 1

What is the triad of haemolytic uraemic syndrome (HUS)?

Answer 1

1. Acute kidney injury
2. Microangiopathic haemolytic anaemia
3. Thrombocytopenia

Seen in very young children; very rare

Question 2

Most cases are secondary (termed typical haemolytic uraemic syndrome).

What are the causes of secondary haemolytic uraemic syndrome?

Answer 2

1. SHIGA toxic producing Ecoli (STEC) 0157:H7 (verotoxigenic / enterohaemorrhagic)
   => most common cause in children >90% of cases
   => acquired from undercooked meat / petting farms
   => verotoxin causes endothelial cell damage to glomerular capillaries & thrombus formation within renal arteries
2. Pneumococcal infection
3. HIV
   * more common in summer and in children <3yrs
4. Rare: systemic lupus erythematousus, drugs, cancer

Question 3

Primary (atypical) haemolytic uraemic syndrome is due complement dysregulation.

Answer 3

INFO CARD

Question 4

What are the signs & symptoms of haemolytic uraemic syndrome?

Answer 4

Symptoms:

1. Bloody diarrhoea
2. Vomiting
3. Abdominal pain
4. Low-grade pyrexia
5. Oliguria / anuria
6. Haematuria
7. Important to ask for risk factors e.g. recent farm visits

Signs:
1. Pale (secondary anaemia)

2. Jaundiced (secondary to haemolysis)
3. Bruising (secondary to thrombocytopenia)
4. Abdominal tenderness
5. Colitis - haemoglobinuria - oliguria - CNS signs - encephalopathy - coma
   * Typical HUS assoc. with diarrhoea, Atypical HUS is not.

Question 5

What are the investigations for haemolytic uraemic syndrome?

Answer 5

1. Bedside: urine dipstick
   => may show haematuria / proteinuria (non-nephrotic ranges)
2. Bloods:
   => FBC shows normocytic anaemia (secondary to haemolysis), thrombocytopenia and possibly raised neutrophil (WCC) count

=> U&E shows raised urea and creatinine (shows AKI)

=> Raised LDH

=> Normal clotting screen

=> Blood film shows reticulocytes (secondary to haemolysis) and schistocytes (fragmented red cells)

3. Stool culture for E.coli
   => PCR for Shiga toxin
4. Coombs test -ve

Question 6

How is haemolytic uraemic syndrome managed?

Answer 6

1. Managed conservatively with supportive measures e.g. fluid for hypovolaemia; blood transfusions; dialysis if severe renal impairment
2. Important to NOT administer antibiotics (this can induce expression and increase release of verotoxin)
3. Treat renal failure
4. Relapses in
   thrombotic thrombocytopenic purpura (TTP) may require steroids, splenectomy, vincristine

Question 6

How is haemolytic uraemic syndrome managed?

Answer 6

1. Managed conservatively with supportive measures e.g. fluid for hypovolaemia, blood transfusions, dialysis if required
2. Important to NOT administer antibiotics (this can induce expression and increase release of verotoxin)