STEC-HUS (Shiga-toxin producing E. coli – HUS)
Also known as “typical HUS” or “Diarrhoea-associated HUS” or “D+HUS”
The commonest cause of an episode of HUS is following infection with Shiga-toxin producing E coli (STEC) – in the UK this is most commonly E.coli O157:H7 (over 80% of cases) however other shiga-toxin producing E.coli serotypes (O111, O26, O145, O103, O104) and Shigella dysentriae have also been implicated, which occur endemically in parts of the world. The peak incidence of STEC infection is in pre-school children, although infection can occur at all ages with another peak in older people.
Following infection with STEC the majority of children develop diarrhoea, which is often bloody in nature. In 85 – 90% this resolves with no further problems, however in 10-15% HUS develops typically occurring one week after the diarrhoea. Renal replacement becomes necessary in 50-60% of cases and extra-renal manifestations occur in approximately 20% and are associated with increased risk of mortality. Following resolution of the acute phase of HUS, approximately 30% of children show evidence of long-term renal complications including hypertension, proteinuria and decreased glomerular filtration rate.
Differentiating between STEC-HUS and aHUS is not always possible at presentation. Diarrhoea is not always a feature of STEC infection. Similarly, a number of patients with HUS subsequently found to be secondary to complement abnormalities present with non-bloody diarrhoea.
Following diagnosis of HUS, (even in the absence of diarrhoea or if diarrhoea has resolved) urgent attention should be paid to finding evidence of STEC infection.
In ALL cases this must include::
- Clinical assessment including a careful history (family members with bloody diarrhoea, local outbreak of STEC, recent travel) and examination (evidence of colitis).
- Stool culture with the use of selective and differential media such as sorbitol MacConkey agar can detect STEC O157, but no selective and differential media exist for the detection of non-O157 STEC strains. A rectal swab should be performed if there is no stool.
- Serology for non-O157 STEC – this is performed at the Public Health England Reference Laboratory
- Stool PCR for stx1 and stx2 genes – this is also performed at the Public Health England Reference Laboratory, although some local microbiology laboratories can perform this test.
It is therefore vital that both stool and serology samples are sent on all patients with HUS to the Public Health England Reference Laboratory as soon as possible. This often requires the clinician to liaise with the local microbiology department to ensure samples are sent urgently.
There is no clear evidence that eculizumab is effective in STEC-HUS, however this intervention will be examined in the ECUSTEC trial in children under 18 years in the UK, commencing 2017.