haemolytic uraemic syndrome (HUS)
Hemolytic uremic syndrome (HUS) is a multisystem thrombotic microangiopathic disease characterized by the triad of renal failure, hemolytic anemia and thrombocytopenia. It is the most common cause of renal failure in infancy and childhood requiring dialysis.
There are two forms of this syndrome:
- typical or D+ HUS: corresponds to >90% of all instances, occurs in childhood, and is caused by Shiga toxin-producing Escherichia coli
- atypical or D- HUS: can occur after infections, use of certain drugs, following other pathologies (e.g. malignancy), or, rarely, due to defective vitamin B12 metabolism
This article is based on the features related to the typical hemolytic-uremic syndrome.
Epidemiology
Hemolytic-uremic syndrome affects ~ 2:100,000 people worldwide . It is most commonly seen in young children.
Clinical presentation
Usually, there is an interval of 2-12 days between the ingestion of contaminated food and the first day of diarrhea and abdominal pain. After 1-3 days the diarrhea becomes bloody (~90%). Fever is usually absent.
Pathology
In over 90% of cases, hemolytic-uremic syndrome occurs following a gastrointestinal infection with Shiga toxin-producing E. coli (STEC). Some cases are associated with medical conditions such as collagen vascular diseases, such as systemic lupus erythematosus, underlying malignancy, or medications such as cyclosporine, oral contraceptives, or 5-fluoro-uracyl.
Injury to the endothelium of the capillaries results in mechanical destruction of the erythrocytes. The kidneys can be the only organ involved; however, involvement of other organs, such as liver, pancreas, heart, intestine, and muscles, is also possible.
Radiographic features
MRI
Bilateral, often symmetric, basal ganglia (especially putamen) and centrum semiovale hyperintensity on T2/FLAIR images, usually due to vasogenic edema.
Foci of diffusion restriction may sometimes be found, especially in the acute phase.
History and etymology
The term was coined by Swiss physician Conrad von Gasser in 1955. E. coli as an etiological factor was proposed by Mohamed A. Karmali in 1985 .
Shiga toxin is named after Japanese physician and bacteriologist Kyoshi Shiga, as is the genus Shigella.
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