Definition of Hemolytic uremic syndrome

Hemolytic uremic syndrome: A condition characterized by the breakup of red blood cells (hemolysis) and kidney failure. There is clumping of platelets (the blood cells responsible for clotting) within the kidney's small blood vessels with resultant ischemia (reduced blood flow) leading to the kidney failure. The partial blockage of the blood vessels also leads to the destruction of red blood cells (hemolysis). Platelets are also decreased which can cause bleeding problems.

There are many causes for the hemolytic uremic syndrome (HUS) including shigella bacteria, drugs, tumors, pregnancy, and systemic lupus erythematosus. One of the most prominent causes today of HUS is a strain of the E. coli bacteria called E. coli O157:H7.

"Hemolytic" refers to the breakup of red blood cells. This leads to anemia and a shortage of platelets (thrombocytopenia) which causes abnormal bleeding. "Uremic" refers to the acute kidney failure. Central nervous system problems with seizures and coma can also occur.

HUS is the most common cause of acute kidney failure in infants and young children. Cases typically begin with severe abdominal cramps and diarrhea which may become bloody by the second or third day. Nausea and vomiting is present in approximately half of the patients. Most patients recover in 7-10 days, but some (6%) go on to have HUS. This is most likely to happen in children and the elderly. Some patients develop neurological problems such as seizures. Many patients require dialysis and blood transfusions. The mortality rate is 3 to 5%.

The E. coli usually are acquired from eating raw or undercooked ground beef (hamburger) or from drinking raw milk or contaminated water. Less commonly, E coli O157:H7 is transmitted from one person to another.

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