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Hemolytic Uremic Syndrome, Post-diarrheal (HUS)
1995 Case Definition
Clinical description
Hemolytic uremic syndrome (HUS) is characterized by
the acute onset of microangiopathic hemolytic anemia, renal injury,
and low platelet count. Thrombotic thrombocytopenic purpura (TTP)
is also characterized by these features but also can include central
nervous system involvement and fever, and may have a more gradual
onset. Most cases of HUS (but few cases of TTP) occur after an acute
gastrointestinal illness (usually diarrheal). Only HUS or TTP occurring
after an acute diarrheal illness is reportable.
Laboratory criteria for diagnosis
The following are present at some time during the illness:
-
Anemia (acute onset) with microangiopathic changes
(i.e., schistocytes, burr cells, or helmet cells) on peripheral
blood smear
-
Renal injury (acute onset), evidenced by either
- Hematuria, or
- Proteinuria, or
- Elevated creatinine level (i.e., greater than or equal to
1.0 mg/dl in a child less than 13 years of age or greater than
or equal to 1.5 mg/dl in an adult, or greater than or equal to
50% increase over baseline)
Note: A low platelet count can usually, but not always,
be detected early in the illness, but it may then become normal or
even high. If a platelet count obtained within 7 days after onset
of the acute gastrointestinal illness is not less than 150,000/mm 3,
other diagnoses should be considered.
Case classification
Probable:
- An acute illness diagnosed as HUS or TTP that meets
the laboratory criteria, but for which circumstances of onset (within
three weeks after onset of acute diarrhea or bloody diarrhea) have
not been determined, or
- An acute illness diagnosed as HUS or TTP, with
onset within 3 weeks of onset of an acute or bloody diarrhea, that
meets the laboratory criteria except that microangiopathic changes
are not confirmed
Confirmed: An acute illness diagnosed as HUS
or TTP, that both meets the laboratory criteria and began within
3 weeks of onset of an acute or bloody diarrhea
Comment
Some investigators consider HUS and TTP to be part
of a continuum of disease. Therefore, criteria for diagnosing TTP
on the basis of central nervous system involvement and fever are
not provided because cases diagnosed clinically as postdiarrheal
TTP should also meet the criteria for HUS. These cases are reported
as postdiarrheal HUS.
See also:
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