Haemolytic Uraemic Syndrome

Question 1

Define HUS

Answer 1

Characterised by microangiopathic haemolytic anaemia, thrombocytopenia and AKI

Question 2

What are the two forms of HUS

Answer 2

D+ Diarrhoea associated

D- no prodromal illness identified

Question 3

Aetiology of HUS

Answer 3

Infection with STEC (Shiga-toxin producing E. coli), specifically EHEC 0157:H7 from contaminated water, meat, dairy etc. (-> bloody diarrhoea, abdominal pain)

Other causes: strep, shigella, HIV, OCP, cyclosporin, chemo, Malignancy, SLE, familial HUS

Question 4

Pathophysiology of HUS

Answer 4

Endothelial injury -> platelet aggregation, release of large vWF multimers + clotting
Small vessel thrombosis
Damage to the endothelium of the glomerular capillary bed -> fibrinoid necrosis -> renal ischaemia and failure

Question 5

Epidemiology of HUS

Answer 5

STEC HUS common in young children <5yrs - Mostly seen in small clusters or sporadically
Overlap with TTP

Question 6

Presenting symptoms of HUS

Answer 6

Anaemia: Fatigue, malaise, SOB
Nausea
Fever <38
GI: severe colic, watery diarrhoea (bloodstained)
Renal: oliguria, anuria, haematuria

Question 7

Signs of HUS

Answer 7

Pallor
Jaundice
Bruising 
Generalised oedema
HTN
Retinopathy 
Abdominal tenderness

Question 8

Investigations for HUS

Answer 8

FBC: macrocytic anaemia, thrombocytopenia
Blood film: schistocytes
U+Es: Raised Ur, Cr, Urate. HyperK, HypoNa
Clotting: Normal
LFTs: UC bilirubin, LDH raised
ABG: met. acidosis
Blood cultures: E. coli

Urinalysis: haematuria, proteinuria
Stool sample: E. coli

Renal biopsy - arteriolar necrosis, glomerular capillary thrombosis if D+