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are often well publicized. HUS is most commonly seen in the summer
months (see Chapter 94 Infectious Disease Emergencies ).
Although children of all ages can develop typical HUS, it most
commonly affects children younger than 5 years. Approximately 5% to
15% of children who develop culture-confirmed STEC gastroenteritis
progress to HUS. The use of antibiotics and antimotility agents appear to
increase the risk of developing HUS with this infection. Early hydration
with IV fluids, especially during the diarrheal phase of illness appears to
decrease the risk for subsequently requiring RRT secondary to HUS.
In the majority of patients with STEC enterocolitis, the illness begins
with watery diarrhea and evolves to hemorrhagic colitis. Vomiting and
severe abdominal pain may occur. Gastrointestinal complications include
bowel wall necrosis, toxic megacolon, peritonitis, intussusception, and
rectal prolapse. The clinical manifestations of HUS generally present 5 to
10 days after the onset of colitis. They may become apparent as the diarrhea
is resolving, and the evolution of the clinical signs may be rapid.
Microangiopathic injury of organs other than the kidneys and intestine
may occur. Pancreatic involvement can be associated with transient or,
rarely, permanent diabetes mellitus. Liver injury may manifest as
hepatomegaly and elevated transaminases. Myocardial ischemia or fluid
overload may lead to cardiac dysfunction. Approximately one-quarter of
children demonstrate some degree of encephalopathy manifested as
irritability and/or somnolence. Some may experience more severe
consequences of CNS involvement including seizures, coma, stroke,
hemiparesis, and cortical blindness.
Clinical assessment. The patient may present pale and lethargic. Jaundice
is present in approximately one-third of patients. Given symptoms of severe
diarrhea and vomiting, the child may present with evidence of hypovolemia
including hypotension and signs of decreased perfusion. Alternatively, if
oral intake has been maintained in the face of oliguric renal failure, signs of
volume excess, including edema and hypertension, may be apparent.

A CBC will show microangiopathic anemia and thrombocytopenia.
Assessment of the blood smear demonstrates fragmented erythrocytes,
schistocytes, and helmet cells. Other studies may include increased
reticulocyte count, elevated indirect bilirubin, increased lactate
dehydrogenase, and decreased haptoglobin. Coagulation studies are