Also known as “typical HUS” or “Diarrhoea-associated HUS” or “D+HUS”
The most common cause of an episode of HUS is following infection with Shiga-toxin producing E coli (STEC). In the UK this is most commonly due to 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% of cases, 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.
Thrombus formation in STEC HUS
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.
- Stool PCR for stx1 and stx2 genes – this can be performed at one of the reference laboratories either the UK Health Security Agency (GBRU) Colindale or Scottish E.coli O157 / STEC Reference Laboratory Edinburgh. Although some local microbiology laboratories can perform this test, we recommend that samples that have yielded negative results should still be forwarded to the reference laboratory.
It is therefore vital that a stool sample or rectal swab is sent on all patients with HUS to the relevant reference laboratory as soon as possible. This often requires the clinician to liaise with the local microbiology department to ensure samples are sent urgently.
In England – samples should be sent to UK Health Security Agency (GBRU) Colindale
In Scotland – samples should be sent to Scottish E.coli o157 / STEC Reference Laboratory Edinburgh
Forms for sending stool or rectal swab samples to the reference laboratories are below.
In addition, it is appropriate to notify the local health protection team cases of suspected STEC – a diagnosis of HUS without positive microbiological confirmation is sufficient to warrant notification. To notify – in England – Find your local health protection team in England – GOV.UK (www.gov.uk)