Definition of Hemolytic uremic syndrome (HUS)
Hemolytic uremic syndrome (HUS) is a condition that results from the abnormal premature destruction of red blood cells. Once this process begins, the damaged red blood cells start to clog the filtering system in the kidneys, which may eventually cause the life-threatening kidney failure associated with hemolytic uremic syndrome.
Most cases of hemolytic uremic syndrome develop in children after two to 14 days of diarrhea — often bloody — due to infection with a certain strain of Escherichia coli (E. coli). Adults also may develop hemolytic uremic syndrome after an E. coli infection, but the cause also may be certain medications, other types of infections, pregnancy or it may be unknown.
Though hemolytic uremic syndrome is a serious condition, getting timely and appropriate treatment leads to a full recovery for most people — especially young children.
Symptoms of Hemolytic uremic syndrome (HUS)
Signs and symptoms of hemolytic uremic syndrome may include:
- Bloody diarrhea
- Abdominal pain
- Pale skin tone
- Fatigue and irritability
- Fever, usually not high and may not be present at all
- Blood in the urine
- Small, unexplained bruises or bleeding from the nose and mouth
- Decreased urination or blood in the urine
- Swelling of the face, hands, feet or entire body
Sometimes neurological symptoms, such as seizures, develop as well.
When to see a doctor
Call your doctor immediately if you or your child experiences unexplained bruises, bloody diarrhea, unusual bleeding, swollen limbs, extreme fatigue or decreased urine output after several days of diarrhea. Seek emergency care if you or your child doesn’t urinate for 12 hours or more.
A number of things can cause hemolytic uremic syndrome, but the most common cause — particularly in children — is an infection with a specific strain of E. coli, usually the strain known as O157:H7. However, other strains of E. coli have been linked to hemolytic uremic syndrome, too.
E. coli refers to a group of bacteria normally found in the intestines of healthy humans and animals. Of the hundreds of types of E. coli, most are harmless. But some strains of E. coli are responsible for serious foodborne infections, including those that can lead to hemolytic uremic syndrome. E. coli may be found in:
- Contaminated meat or produce
- Swimming pools or lakes contaminated with feces
Most people who are infected with E. coli, even the more dangerous strains, won’t develop hemolytic uremic syndrome. It’s also possible for hemolytic uremic syndrome to follow infection with other types of bacteria.
In adults, hemolytic uremic syndrome is more commonly caused by other factors, including:
- The use of certain medications, such as quinine (an over-the-counter muscle cramp remedy), some chemotherapy drugs, the immunosuppressant medication cyclosporine (Neoral, Sandimmune) and anti-platelet medications
- Certain infections, such as HIV/AIDS or an infection with the pneumococcal bacteria
- Genes, which can be a factor because a certain type of HUS — atypical hemolytic uremic syndrome — may be passed down from your parents
The cause of hemolytic uremic syndrome in adults is often unknown.
Those most at risk of developing hemolytic uremic syndrome are:
- Children under 5 years of age
- People who have certain genetic changes that make them more susceptible
Young children and elderly adults are the most likely to be seriously ill from hemolytic uremic syndrome.
Complications of Hemolytic uremic syndrome (HUS)
Hemolytic uremic syndrome can cause a number of serious, life-threatening complications, including:
- Sudden (acute) kidney failure
- High blood pressure
- Chronic kidney failure
- Heart problems
Preparing for your appointment
Because most people with hemolytic uremic syndrome are admitted to the hospital after a trip to the emergency room or following a brief phone call or visit with their doctors, it’s not likely that you or your child will have a routine office visit.
However, if you or your child is experiencing symptoms of hemolytic uremic syndrome after several days of diarrhea, call your doctor immediately and be prepared to answer these questions:
- Have you noticed blood in your or your child’s diarrhea?
- What other signs and symptoms — such as fever, swelling or decreased urine output — have you or your child experienced?
- How long have you or your child been experiencing these symptoms?
- How long has it been since you or your child urinated?
What you can do in the meantime
If you or your child has an illness that causes vomiting or diarrhea, it’s a good idea to try to replace the fluids that have been lost with an oral rehydrating solution, such as CeraLyte, Pedialyte or Oralyte. Don’t give yourself or your child any medication to stop diarrhea if you see any evidence of blood in the stool. These medications, such as bismuth subsalicylate (Kaopectate, Pepto-Bismol) and loperamide (Immodium), may increase the risk of hemolytic uremic syndrome.
Tests and diagnosis
If your doctor suspects hemolytic uremic syndrome, various lab tests may be done to confirm the diagnosis.
- Blood tests. Blood tests may reveal a low platelet count, low red blood cell count or a higher than normal level of creatinine — a breakdown product of creatine, an important part of muscle — in your blood. A blood sample can also be used to determine if your red blood cells are damaged.
- Urine test. Your doctor may also collect a urine sample to test for blood in your urine.
- Stool sample. Additionally, your doctor may take a stool sample to test for the presence of bacteria.
Treatments and drugs
Hemolytic uremic syndrome requires treatment in the hospital. To ease immediate signs and symptoms and prevent further problems, hemolytic uremic syndrome treatment may include:
- Fluid replacement. Lost fluid and electrolytes need to be carefully replaced because the kidneys aren’t removing fluids and waste as efficiently as normal.
- Red blood cell transfusions. If you don’t have enough red blood cells, you may feel chilled, fatigued and short of breath. You may have a rapid heart rate, yellow skin and dark urine. Red blood cell transfusions, given through an intravenous (IV) needle, may help reverse these signs and symptoms.
- Platelet transfusions. If you’re bleeding or bruising easily, platelet transfusions can help your blood clot more normally. Like red blood cell transfusions, platelet transfusions are given through an IV needle.
- Plasma exchange. Plasma is the part of blood that supports the circulation of blood cells and platelets. Sometimes a machine is used to clear the blood of its own plasma and replace it with fresh or frozen donor plasma. This process is called plasmapheresis.
- Kidney dialysis. Sometimes dialysis is needed to filter waste and excess fluid from the blood. Dialysis is usually a temporary treatment until the kidneys begin functioning adequately again. If the kidney damage is significant, however, permanent kidney failure — requiring long-term dialysis or a kidney transplant — is possible.
Despite the severity of the condition, appropriate treatment leads to a full recovery for most people with hemolytic uremic syndrome — especially young children.
In those who have some lasting kidney damage, following a low-protein diet and taking the blood pressure lowering medications known as angiotensin-converting enzyme (ACE) inhibitors if blood pressure is high may prevent or delay further kidney damage.
A less common type of hemolytic uremic syndrome called atypical hemolytic uremic syndrome also is treated with plasma exchange. The Food and Drug Administration has approved the use of a medication called eculizumab (Soliris) for the treatment of atypical hemolytic uremic syndrome. Eculizumab is a type of medication known as a monoclonal antibody. It prevents the continued destruction of healthy cells. However, this medication has a significant risk of serious infection. If possible, you or your child may receive the meningococcal vaccine before receiving this medication.
Specific preventive measures for hemolytic uremic syndrome aren’t clear. However, it’s always a good idea to take precautions against E. coli and other foodborne illnesses. It’s important to note that meat or produce contaminated with E. coli won’t necessarily look, feel or smell bad. Things you can do that will help reduce your risk of foodborne illness:
- Wash your hands, utensils and food surfaces often.
- Keep raw foods separate from ready-to-eat foods.
- Defrost raw meat in your microwave or refrigerator. (Don’t leave meat on the counter to thaw.)
- Thoroughly cook ground beef to at least 160 F (71 C) throughout. Check the temperature of the meat with a thermometer. When reheating already cooked burger patties, make sure the internal temperature reaches 165 F (74 C).
- Wash fruits and vegetables under running water.
- Avoid unpasteurized milk, juice and cider.
- Avoid swimming in water potentially contaminated with feces, and don’t swim if you have diarrhea.
Also make sure that everyone in your family — including children — washes his or her hands after using the toilet or changing diapers and before eating. In child care facilities, diapers shouldn’t be changed or disposed of in the same room where food is prepared or eaten.