Hemolytic-uremic syndrome (HUS)

Hemolytic-uremic syndrome (HUS)

Definition:

HUS is a disorder marked by renal failure, hemolytic anemia, thrombocytopenia (platelet deficiency), coagulation defects, and variable neurologic signs.

Alternative Names:

HUS

Causes, incidence, and risk factors:

This disorder is most common in children. It frequently occurs after a gastrointestinal (enteric) infection, often one caused by a specific 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.

The incidence of HUS, once relatively rare, is increasing in children. It is the most common cause of acute renal failure in children. Several large outbreaks in 1992 and 1993 were attributed to undercooked hamburger contaminated with E. coli. Because of this association new labeling will appear on supermarket hamburger and temperature guidelines have been published for cooked hamburger at fast food chains and restaurants.

HUS is less common in adults. Most adult cases have been reported in patients with cancer who have received the chemotherapy drug 5-FU.

Predisposing risk factors are not known. It has been occasionally reported in association with a variety of other diseases and infections. The incidence is 1 out of 10,000 people.

HUS often begins with vomiting and diarrhea (which may be bloody). Within a week the patient develops weakness and irritability. Urine output decreases dramatically and may almost cease. Because red blood cells are being destroyed (a process called hemolysis) the patient rapidly becomes anemic and pale.

Symptoms:

Early symptoms:

Later developing symptoms:

Low urine output (oliguria)
No urine output (anuria)
Pallor
Bruising
Skin rash that looks like fine red spots (petechiae)
Yellowish coloration to the skin (jaundice)
Consciousness - decreased
Seizures -- rare

Signs and tests:

Physical examination may show an enlarged liver or spleen. There may be variable, abnormal neurological changes. There is laboratory evidence of hemolytic anemia and acute renal failure.

A CBC demonstrates:
- Decreased platelets (thrombocytopenia).
- Rupture of red blood cells (hemolysis).
- Anemia from loss of red blood cells (hemolytic anemia).
- Elevated white blood count.
The platelet count may be decreased.
Coagulation studies such as PT and PTT may be normal or abnormal.
Blood chemistry such as a chem-20 shows abnormalities.
- The BUN is elevated.
- The creatinine is elevated.
- Free hemoglobin is elevated.
A urinalysis demonstrates:
- Blood in the urine (hematuria).
- Protein in the urine (proteinuria).
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 specific type of E. coli.
Kidney biopsy (renal biopsy) shows diagnostic changes.

Treatment:

This is a serious complicating illness in both children and adults, and death may occur. The treatment is supportive.

Transfusions of packed red cells and platelets are given as needed. Kidney dialysis may be indicated. Medications prescribed include corticosteroids and aspirin.

Plasmapheresis, also called plasma exchange (or passage of the plasma through a Protein A filter) may be performed, although its role is much less well documented than in TTP (thrombotic thrombocytopenic purpura).

The blood plasma (the portion that does not contain cells, but does contain antibodies) is removed and replaced with fresh (donated) plasma or filtered to remove antibodies from the circulation.

Expectations (prognosis):

About 60% of individuals receiving treatment will recover, and the outcome is better in children.

Complications:

Chronic or relapsing HUS
Acute renal failure
Chronic renal failure
Uremia (symptoms caused by accumulation of nitrogen-containing wastes in the body)

Calling your health care provider:

Call your health care provider if symptoms of HUS develop. Decreased consciousness, blood in the stool, and absent urine output indicate an emergency situation.

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

Prevention:

The known cause, E. coli in hamburger and ground meats, can be prevented by adequate cooking. Other unrecognized causes may not be preventable at this time.

Review Date: 11/4/2001
Reviewed By: Rebecca Elstrom, M.D., Division of Hematology-Oncology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.

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