HUS

Alternative names
Hemolytic-uremic syndrome

Definition
HUS is a disorder marked by kidney failure, hemolytic anemia, thrombocytopenia (platelet deficiency), coagulation defects, and variable nervous system signs.

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.

HUS, once relatively rare, is increasing in children. It is the most common cause of acute kidney failure in children. Several large outbreaks in 1992 and 1993 were attributed to undercooked hamburger contaminated with E. coli. Because of this association, supermarket hamburger has new labeling, and there are new temperature guidelines for hamburger cooked 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. HUS occasionally occurs in association with a variety of other diseases and infections. About 1 in 10,000 people get it.

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:

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

     
  • A complete blood count (CBC) might show:       o Decreased platelet count (thrombocytopenia)       o Rupture of red blood cells       o Anemia from loss of red blood cells (hemolytic anemia)       o Elevated white blood count  
  • Coagulation studies such as PT and PTT may be normal or abnormal.  
  • Blood chemistry such as a chem-20 shows abnormalities, such as:       o BUN is elevated       o Creatinine is elevated       o Free hemoglobin is elevated  
  • A urinalysis demonstrates:       o Blood in the urine       o 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 specific type of E. coli.  
  • Kidney 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 filter) may be performed, although its role is not completely clear.

In plasmapharesis, 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.

Johns Hopkins patient information

Last revised: December 6, 2012
by Dave R. Roger, M.D.

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