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Hemolytic Uremic Syndrome

Hemolytic Uremic Syndrome, also called HUS, is a severe, life threatening condition that results in an abnormal destruction of red blood cells and can lead to kidney failure. It occurs in about 10% of those who become infected with Escherichia coli O157: H7 or any other Shiga toxin-producing E. coli, Shigella, Legionella pneumophila, and Campylobacter.

HUS Fast Facts

  • HUS is characterized by abnormal destruction of red blood cells. The damaged red blood cells can then clog the filtering system of the kidneys and result in life-threatening kidney failure.
  • HUS is the most common cause of acquired acute kidney failure in children and infants. Adolescents, adults and elderly are also susceptible to the disease.
  • The first symptoms of HUS include: vomiting, diarrhea, abdominal pain, lethargy, etc.
  • There is no one test that confirms the development of HUS. To confirm the disease, a combination of urine tests, blood tests, and stool samples are taken.
  • Treatment of HUS revolves around medical and family history, test results, and a kidney biopsy. Treatments may include: supportive care, blood transfusions, dialysis, plasma exchanges, etc.

What is HUS?

Hemolytic uremic syndrome, or HUS, is a potentially fatal form of kidney failure. HUS was first described in medical literature as a syndrome in 1955. But it was not until 1982 that doctors learned that HUS was a secondary complication of E. coli infections.

HUS involves 2 body systems – the kidneys and the blood stream. In foodborne-based HUS, blood within the body’s capillaries begins to clot abnormally from dead red blood cells killed by Shiga toxins. Capillaries are the smallest blood vessels in your body, so when the red blood cells pass through them, they are torn apart and broken. Once this happens, waste products in the bloodstream are not able to get filtered by the kidneys, which leads to buildup of urea and other waste products in the bloodstream. This can lead to blood stream infection and kidney failure.

HUS is related to yet another condition that leads to the same clotting process within the capillaries called thrombotic thrombocytic purpura (TTP). HUS is just more widely known because of its relation to E. coli strains and other Shiga toxin-producing (STEC) E. coli strains that lead to food poisoning.

HUS is classified into two types:

  • Typical HUS: This kind of HUS is preceded by foodborne illnesses and gastrointestinal symptoms such as vomiting, diarrhea, etc.
  • Atypical HUS: This kind of HUS is not associated with any gastro-intestinal symptoms.

What are the Causes of Hemolytic Uremic Syndrome?

  • E. coli/ ShigellaE. coli, Shigella, and other Shiga toxin producing bacteria cause food poisoning in individuals and result in symptoms such as vomiting, diarrhea (usually bloody), and abdominal cramps. These bacteria spread to humans through contaminated food (undercooked meat and seafood, improperly handled fruits and vegetables), contaminated water or by the feces of infected people. STEC E. coli accounts for around 36% of the total cases of E. coli.

HUS is generally preceded by bloody diarrhea. As the E. coli bacterium rapidly multiplies in the intestine and tightly binds to the cells in the large intestine, it emits a toxin called a Shiga toxin. This attachment makes it easier for the toxin to seep into the intestinal capillaries. It further attaches itself to the weak receptor on white blood cells, thus allowing the toxins to ride to the kidneys. The toxin then, moves into the interior of the cell, shuts down the protein machinery, and results in cellular destruction (or rather, cell death). This gives birth to coagulation and clots ultimately leading to kidney failure.

The body’s red blood cells are either destroyed by the Shiga toxin or become damaged as they try to pass through the partially obstructed microvessels.

  • Pregnancy– Sometimes pregnancy and use of birth control pills during early postpartum period could be associated with HUS.
  • Pneumoniathat is caused by Streptococcus pneumoniae. HUS is a very rare complication of this infection. It is the cause of 40% of atypical HUS.
  • Medications: Certain medications, such as birth control pills, chemotherapy, immunosuppression drugs, ticlopidine etc., can be associated with HUS.
  • AIDSis also sometimes associated with HUS.

What are the Signs and Symptoms of HUS?

Within a week after an infected person ingests Shiga-toxin producing E. coli, the bacteria will nest and severely inflame the colon – causing bloody diarrhea. These symptoms occur about a week prior to any potential onset of HUS. Other symptoms that occur, apart from bloody watery diarrhea, are vomiting and abdominal cramping. Other symptoms of HUS include:

  • abdominal pain
  • bloody diarrhea
  • fever
  • fatigue
  • decreased urination
  • dehydration
  • pale skin
  • unexplained bruises and bleeding

Since the pain of HUS occurs in the right lower part of the abdomen, it is often mistaken for appendicitis. But, once colonoscopy is conducted, severe inflammation, ulceration, and pseudomembranes (made of sloughed mucosal cells, white blood cells, and fibrin) can indicate HUS disease.

The symptoms can resolve before the kidney failure and anemia associated with HUS occurs.

How is HUS Diagnosed?

Depending upon the history and medical condition related to the symptoms of HUS expressed, a health care provider will typically look for some abnormal findings through the following tests:

  • Hemolytic Anemia: Red blood cell counts will come as low and in a peripheral blood smear, a test in which blood is examined through a microscope will show that red blood cells are damaged and destroyed.
  • Urine Tests: Blood and protein can be found in the urine.
  • Stool Cultures: A physician will search for culture strains of E. coli from stool samples. The body sheds the bacteria from the body in a week, so a negative test does not rule out the case for HUS.
  • Uremia: Functions of the kidneys are measured by testing the level of waste products. An increase in blood urea nitrogen and creatinine indicates kidneys are not functioning properly.

How is HUS Treated?

HUS is a severe condition requiring hospitalization. A person with HUS needs urgent medical attention and cannot be treated from home. Current treatments for HUS include:

  • Fluid Replacement: Fluids and electrolytes are replaced as kidneys are not moving the fluids and waste now.
  • Red Blood Cell Transfusions: An IV needle can transfuse red blood cells, thus, easing on the symptoms, such as chills, fatigue, yellow skin, dark urine, etc.
  • Plasma Exchange: Plasma helps in circulation of blood cells and platelets. Removing the plasma and replacing it with a donor plasma can help in circulation.
  • Kidney Dialysis: Dialysis can be done until the kidneys go on to work as normal.
  • In severe cases, a kidney transplant may be necessary.

What are the Long-Term Complications of HUS?

Scientific studies and medical analyses have shown the following complications related to HUS:

  • 3-5% of people with HUS die.
  • Apart from renal failure, potential brain damage and multi-organ damage is also one of the causes of death due to HUS as there is a lack of oxygenated blood circulating throughout the body.
  • There may be central nervous system issues, such as stroke or coma.
  • Majority of those affected recover completely, but around 30% may be left with a residual renal injury.
  • HUS patients can also develop future complications in other parts of their bodies, such as hypertension, proteinuria, and low glomerular filtration rate.

The early onset of medical intervention in someone with HUS is recommended to help reduce the risk of long-term complications.

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