Chapter 31 Hemolytic-Uremic Syndrome
PATHOPHYSIOLOGY
Hemolytic-uremic syndrome (HUS) is the leading cause of acute renal failure in infants and young children. HUS is a systemic disease that consists of the following symptomatology: (1) renal failure, (2) hemolytic anemia with fragmented red blood cells and platelets, and (3) thrombocytopenia. Although the exact cause is not known, HUS generally follows an episode of gastroenteritis caused by a strain of Escherichia coli O157:H7, or other enteric pathogens such as Shigella, Salmonella, and Campylobacter. Less commonly, the disease follows an upper respiratory tract infection. The clinical manifestations result from changes in the capillary endothelium caused by the etiologic agent. The endothelial changes result in the following pathologic responses: (1) mechanical trauma to erythrocytes and platelets, which shortens their life span and results in anemia and thrombocytopenia; and (2) decreased renal blood flow and glomerular filtration rate, which results in cortical necrosis and consequent renal failure and acquired hemolytic anemia in infants and children. The severity of the condition varies. The prognosis is related to the efficacy, aggressiveness, and promptness of treatment.
INCIDENCE
1. Most commonly seen in children under the age of 4 years
2. Can occur in geographic outbreaks
3. A seasonal variation exists, with an increased incidence during spring and fall
4. The incidence of hypertension as a long-term complication varies from 10% to 50%.
5. Hemolytic-uremic syndrome affects males and females equally.
CLINICAL MANIFESTATIONS
Prodromal Phase
1. Episodes of diarrhea (may be bloody), vomiting, fever, and abdominal pain
2. In older children, may resemble an upper respiratory tract illness
3. Prodromal symptoms may last 1 to 2 weeks, whereas other symptoms may recur in children who appear to have recovered; severity varies. (See Box 31-1 for three types of clinical manifestation.)
Acute Phase
2. Oliguria or anuria for longer than 1 week, then diuresis
3. Renal failure (metabolic disturbance or acidosis; hypocalcemia or hyperkalemia)
4. Abdominal pain (caused by splenic enlargement or gastrointestinal [GI] involvement)
