Haemolytic Uraemic Syndrome and Thrombotic Thrombocytopaenic Purpura

Question 1

Define Haemolytic Uraemic Syndrome (HUS) and Thrombotic Thrombocytopaenic Purpura (TTP)?

Answer 1

A triad of:

• Microangiopathic Haemolytic Anaemia (MAHA)
• Acute Renal Failure
• Thrombocytopaenia

Question 2

What are the two forms of HUS?

Answer 2

D+ = Diarrhoea-associated form
D-  = No prodromal illness identified

Question 3

What are the additional features when HUS overlaps with TTP?

Answer 3

Fever

Fluctuating CNS signs

Question 4

What is the aetiology of HUS and TTP?

Answer 4

Endothelial injury results in platelet aggregation and the release of unusually large vWF multimers and activation of platelets and the clotting casade
This leads to small vessel thrombosis
The glomerular-afferent arteriole and capillaries are particularly vulnerable - they undergo fibrinoid necrosis
This leads to renal ischaemia and acute renal failure
The thrombi also promote intravascular haemolysis

Question 5

What are the infective causes of HUS and TTP?

Answer 5

Escherichia coli (O157)
Shigella
Neuraminidase-producing infections
HIV

Question 6

What drugs cause HUS and TTP?

Answer 6

COCP
Ciclosporin
Mitomicin
5-fluorouracil

Question 7

What are the other causes of HUS and TTP?

Answer 7

Malignant Hypertension
Malignancy 
Pregnancy 
SLE
Scleroderma

Question 8

What is the epidemiology of HUS and TTP?

Answer 8

Uncommon
D+ HUS often affects YOUNG CHILDREN
It is the most common cause of acute renal failure in children
TTP mainly affects ADULT FEMALES

Question 9

What are the GI presenting symptoms of HUS and TTP?

Answer 9

Severe abdominal colic

Watery diarrhoea that becomes bloodstained

Question 10

What are the general symptoms of HUS and TTP?

Answer 10

Malaise
Fatigue
Nausea
Fever < 38 degrees (D+)

Question 11

What are the renal symptoms of HUS and TTP?

Answer 11

Oliguria or anuria

Haematuria

Question 12

What are the General signs of HUS and TTP on physical examination?

Answer 12

Pallor
Slight Jaundice (due to haemolysis)
Bruising 
Generalise oedema
Hypertension
Retinopathy

Question 13

What is the GI sign of HUS and TTP?

Answer 13

Abdominal Tenderness

Question 14

What are the CNS signs of TTP?

Answer 14

Weakness
Reduced Vision
Fits
Reduced consiousness

Question 15

What investigations do you do for HUS and TTP?

Answer 15

FBC 
U&Es 
Clotting 
LFTs
Blood cultures 
ABG 
Blood film
Urine 
Stool samples
Renal biopsy

Question 16

What do we look for specifically on a FBC for HUS and TTP?

Answer 16

Normocytic anaemia
High neutrophils
Very low platelets

Question 17

What do we look for on U&Es for HUS and TTP?

Answer 17

High Urea
High Creatinine
High K+
Low Na+

Question 18

What do we look for on a Clotting Screen for HUS and TTP?

Answer 18

Normal APTT and fibrinogen levels (abnormality may indicate DIC)

Question 19

What do we look for on LFTs for HUS and TTP?

Answer 19

High unconjugated bilirubin

High LDH from haemolysis

Question 20

What do we look for on an ABG for HUS and TTP?

Answer 20

Low pH
Low bicarbonate
Low PaCO2
Normal anion gap

Question 21

What do we see on a Blood Film for HUS and TTP?

Answer 21

Schistocytes

High reticulocytes and spherocytes

Question 22

What do we see on an Urinalysis for HUS and TTP?

Answer 22

1 + g protein/24 hrs

Haematuria

Question 23

How do we use Stool Samples for HUS and TTP?

Answer 23

MC&S

Question 24

Why do we do a Renal Biopsy for HUS and TTP?

Answer 24

Can distinguish between D+ and D- HUS