Haemolytic Uraemic syndrome

Question 1

What is haemolytic uraemic syndrome?

Answer 1

thrombotic microangiopathy in which microthrombi, consisting primarily of platelets, form + occlude arterioles + capillaries.

Question 2

What is the most common cause of HUS?

Answer 2

EHEC O157:H7 E Coli infection

Usually transmitted via contaminated foods (e.g. undercooked beef or raw leafy vegetables)

Question 3

Describe the typical presentation of a patient with HUS

Answer 3

Preschooler
Diarrheal illness for 5–10 days
Petechiae, jaundice, + oliguria.

Question 4

List 2 GI symptoms of HUS

Answer 4

Abdominal pain

Bloody diarrhoea

Question 5

What are the 2 forms of HUS?

Answer 5

D+ = diarrhoea-associated form  
D- = no prodromal illness identified

Question 6

Describe the aetiology of HUS

Answer 6

Toxins cause endothelial damage, stimulating cytokine release
This promotes vasoconstriction + platelet microthrombus formation at the site of damage (thrombocytopenia)
RBCs are mechanically destroyed as they pass through the platelet microthrombi occluding small blood vessels (Haemolysis)
This results in end-organ ischemia + damage, esp in the kidneys (decreased GFR)

Question 7

What triad of pathologies arise in HUS? What symptoms do these give rise to?

Answer 7

Thrombocytopenia: Petechiae, purpura, Mucosal bleeding, Prolonged bleeding after minor cuts
MAHA: Fatigue, dyspnea, pallor, Jaundice
AKI: Hematuria, proteinuria, Oliguria, anuria

Question 8

What haemolytic measurements would be seen in HUS?

Answer 8

Low Hb 
Low Haptoglobin
High BR 
High Reticulocytes
High LDH

Question 9

What is found on the blood film in HUS?

Answer 9

Schistocytes

Question 10

Describe the coagulation profile in HUS

Answer 10

Low Platelets
Normal/ slightly elevated PT + aPTT
High Fibrin degradation products
High D-dimer levels

Question 11

What other blood parameters are seen in HUS?

Answer 11

High WBC count

Negative Coombs test