Diagnosis
Hemolytic anemia and renal failure following bloody diarrhea.
Epidemiologic Risks
Diarrhea from E. coli O157:H7 a common strain in the colon of cows and other herbivores. When slaughtered they get covered in their stool, which is mixed into the meat that you eat, especially hamburger.
Other E. coli strains can lead to HUS, including 06 (PubMed) and O104:H4 (PubMed).
Microbiology
Enterohemorrhagic Escherichia coli; diagnosis of O157:H7 EHEC infection is made on the basis that these strains ferment sorbitol slowly and form white, rather than red, colonies on sorbitol-MacConkey agar plates.
It can also be caused from bacteremic Streptococcus pneumoniae (PubMed)(PubMed). The mechanism is here "These clinical isolates of HUS pneumococci efficiently bound human plasminogen via the bacterial surface proteins Tuf and PspC. When activated to plasmin at the bacterial surface, the active protease degraded fibrinogen and cleaved C3b. Here, we show that PspC is a pneumococcal plasminogen receptor and that plasmin generated on the surface of HUS pneumococci damages endothelial cells, causing endothelial retraction and exposure of the underlying matrix (PubMed)."
Empiric Therapy
Supportive. Antibiotics only serve to increase the risk of HUS from E. coli. Azithromycin will decrease shedding, but whether to treat is uncertain (PubMed) and I would not.
And the disease may be preventable with daily intestinal lavage with polyethylene glycol (PubMed).
Eculizumab, an inhibitor of terminal complement, is effective in atypical HUS (PubMed) but is very expensive and as infectious complications.
Pearls
Antibiotics only serve to increase the risk of HUS from E. coli, especially quinolones which can cause an increase in shiga toxin production. Beta lactams, probably not, but you wanna bet your patients life (PubMed)?
Rants
Treatment of O157:H7 diarrhea may help precipitate HUS. Long term O157:H7 associated with an increased risk for hypertension, renal impairment, and self-reported cardiovascular disease (PubMed).