Hemolytic Uremic Syndrome
Alternate Names : HUS
Hemolytic uremic syndrome is a poorly understood condition that affects the blood and kidneys. It usually follows an infection that has caused diarrhea.
What is going on in the body?
There are many causes for HUS. By far, the most common cause is an episode of diarrhea caused by infection with a special strain of the bacterium, E. coli. There have been a number of epidemics of HUS in recent years linked to eating undercooked beef containing this strain of bacterium. This bacterium produces a toxin that is very harmful to cells, particularly those of the kidneys, blood vessels, and intestinal lining. There are other less common causes of HUS in which the exact cause is not as clear.
HUS is thought to develop when the lining of small blood vessels become damaged. This most commonly occurs in the blood vessels that supply blood to the kidney. The damage causes the blood vessels to swell. Tiny blood clots can form in affected blood vessels, narrowing the vessels or blocking them completely. Because blood cannot pass through these blocked or narrowed vessels, the kidneys are less able to filter waste products from the body and may become damaged. Certain cells in the blood, such as red blood cells that carry oxygen and platelets that help clot the blood, are damaged as they try to pass the narrowed vessels. This leads to anemia, or low blood counts, and poor clotting ability.
Most cases of HUS affect infants and young children between the ages of 7 months and 4 to 6 years. Between 0.3 and 10 per 100,000 children develop HUS in the U.S. each year. The condition tends to occur in epidemics.
What are the causes and risks of the condition?
The most common cause of HUS is the special strain of E. coli bacteria, called E. coli 0157:H7.
Less common causes of this condition include:
other bacteria and viruses
inherited factors
pregnancy
certain medications
organ transplants, such as heart transplant, liver transplant, pancreas transplant, or lung transplant
certain types of cancer
In some cases, there is no obvious cause for the illness.
Several factors put a person at risk for acquiring the diarrhea-related form of HUS. These cases are due to contamination of the substance with the special strain of E. coli bacteria. Examples of substances that may be contaminated include:
raw or undercooked beef
unpasteurized milk or fruit juice, especially apple juice
contaminated water. This is common in underdeveloped countries without proper water treatment, or lakes and ponds near farms that either have cattle or use manure.
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