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Hemolytic-uremic syndrome

Definition

Hemolytic-uremic syndrome (HUS) is a disorder that occurs when an infection in the digestive system produces toxic substances that destroy red blood cells. It often affects the kidneys.

Alternative Names

HUS

Causes, incidence, and risk factors

This disorder is most common in children. It often occurs after a gastrointestinal (enteric) infection, caused by a type of E. coli bacteria (Escherichia coli O157:H7). It has also been associated with other enteric infections, including Shigella and Salmonella, and some non-enteric infections.

HUS was once very rare, but it is increasing in children. It is the most common cause of acute kidney failure in children. Several large outbreaks in 1992 and 1993 were linked to undercooked hamburger meat contaminated with E. coli. Because of these outbreaks, supermarket hamburger meat now has new labeling, and there are new temperature guidelines for hamburgers cooked at fast-food chains and restaurants.

HUS is more complicated in adults. It is similar to another disease called thrombotic thrombocytopenic purpura (TTP).

Other risk factors for HUS are unknown. HUS may occur with a variety of other diseases and infections.

Symptoms

HUS often begins with vomiting and diarrhea (which may be bloody). Within a week, the person may become weak and iritable. People with HUS may urinate far less than normal. Urine output may almost stop. Because red blood cells are being destroyed (a process called hemolysis), the person quickly becomes anemic and pale.

Early symptoms:

• Fever
• Vomiting and diarrhea
• Blood in the stools
• Irritability
• Weakness
• Lethargy

Later developing symptoms:

• Low urine output
• No urine output
• Paleness
• Bruising
• Skin rash that looks like fine red spots (petechiae)
• Yellowish coloration to the skin (jaundice)
• Decreased consciousness
• Seizures -- rare

Signs and tests

A physical exam may show an enlarged liver or spleen. There may be abnormal changes to the nervous system. Lab tests will show signs of hemolytic anemia and acute renal failure.

• A complete blood count (CBC) might show:
  • Lower platelet count (thrombocytopenia)
  • Rupture of red blood cells
  • Anemia from loss of red blood cells (hemolytic anemia)
  • Raised white blood count
• Coagulation studies such as PT and PTT may be normal or abnormal.
• Blood chemistry such as a chem-20 shows abnormalities, including:
  • High BUN level
  • High creatinine level
  • High free hemoglobin level
• A urinalysis shows:
  • Blood in the urine
  • Protein in the urine
• A urine protein test can be used to show the amount of protein in the urine.

Other tests:

• Stool culture may be positive for a certain type of E. coli bacteria
• Kidney biopsy shows changes

Treatment

This is a serious illness in both children and adults, and it can cause death.

People with this condition receive transfusions of packed red cells and platelets as needed. Some people may need kidney dialysis. Doctors may prescribe medications such as corticosteroids.

Some people may have the liquid portion of their blood (plasma) treated with plasmapheresis or plasma exchange. The plasma is removed and replaced with fresh (donated) plasma or filtered to remove antibodies from the blood.

Expectations (prognosis)

More than half of people who get treatment will recover, and the outcome is better in children.

Complications

• Chronic or relapsing HUS
• Acute kidney failure
• Chronic kidney failure
• Uremia (symptoms caused by the build-up of nitrogen-containing wastes in the body)
• Hemolytic anemia
• Thrombocytopenia (lack of enough platelets)
• Problems with blood coagulation
• Problems with the nervous system

Calling your health care provider

Call your health care provider if you develop symptoms of HUS. If you have reduced consciousness, blood in the stool, or a lack of urination, it is an emergency situation.

Call your health care provider if you have had an episode of HUS, and your urine output decreases or you develop other new symptoms.

Prevention

You can prevent the known cause, E. coli, by cooking hamburger and ground meats well. It is not possible to prevent other, unrecognized causes at this time.

Review Date:4/27/2007
Reviewed By:Rita Nanda, M.D., Department of Medicine, Section of Hematology/Oncology, University of Chicago Medical Center, Chicago, IL. Review provided by VeriMed Healthcare Network.

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