Hemolytic-uremic syndrome

Synonyms

2

Overview

Hemolytic uremic syndrome HUS  is a condition caused by the abnormal destruction of red blood cells. The damaged red blood cells clog the filtering system in the kidneys, which can lead to life-threatening kidney failure.

HUS usually develops in children after five to 10 days of diarrhea, often bloody, caused by infection with certain strains of Escherichia coli (E. coli) bacteria. Adults also can develop HUS due to E. coli or other types of infection, certain medications, or pregnancy. HUS is a serious condition. But timely and appropriate treatment leads to a full recovery for most people, especially young children.

Hemolytic uremic syndrome should be distinguished from atypical hemolytic uremic syndrome (aHUS). The two conditions have different causes and different signs and symptoms.

Symptoms

Signs and symptoms of HUS can include:

• Bloody diarrhea
• Decreased urination or blood in the urine
• Abdominal pain, vomiting and occasionally fever
• Pallor
• Small, unexplained bruises or bleeding from the nose and mouth
• Fatigue and irritability
• Confusion or seizures

• High blood pressure
• Swelling of the face, hands, feet or entire body

See your doctor immediately if you or your child experiences bloody diarrhea or several days of diarrhea followed by:

• Decreased urine output
• Unexplained bruises
• Unusual bleeding
• Extreme fatigue

Seek emergency care if you or your child doesn't urinate for 12 hours or more.

Causes

The most common cause of HUS, particularly in children under the age of 5, is infection with E. coli bacteria that produce the toxin called  "Shiga toxin". E. coli refers to a group of bacteria normally found in the intestines of healthy humans and animals. Most of the hundreds of types of E. coli are normal and harmless. But some strains of E. coli, including those that cause HUS, are responsible for serious foodborne infections.

E. coli can be found in:

• Contaminated meat or produce
• Swimming pools or lakes contaminated with feces

Sometimes, E. coli infection is spread through close contact with an infected person, such as within a family or at a day care center. Most people who are infected with E. coli, even the more dangerous strains, don't develop HUS. Other causes of HUS can include:

• The use of certain medications, such as quinine sulfate (Qualaquin), some chemotherapy medications, medications containing the immunosuppressant cyclosporine (Neoral, Sandimmune, Gengraf) and anti-platelet medications
• Certain infections, such as HIV/AIDS or an infection with the pneumococcal bacteria
• Rarely, pregnancy

Susceptibility to an uncommon type of HUS, known as atypical HUS, primary HUS or complement-mediated HUS, can be passed down genetically to children. People who have inherited the mutated gene that causes atypical HUS won't necessarily develop the condition. The mutated gene might be activated after an upper respiratory or abdominal infection.

Prevention

Prophylactic eculizumab treatment maintained chronic suppression of complement activity and reduced graft failure in a patient with CFH mutation and recurrent HUS.

The risk of developing HUS  is highest for:

• Children under 5 years of age
• People over 75
• People with certain genetic changes that make them more susceptible

Diagnosis

To confirm a diagnosis of HUS, your doctor is likely to recommend lab tests, including:

• Blood tests. These tests can determine if your red blood cells are damaged. Blood tests can also reveal a low platelet count, low red blood cell count or a higher than normal level of creatinine, a waste product normally removed by your kidneys.
• Urine test. This test can detect abnormal levels of protein, blood and signs of infection in your urine.
• Stool sample. This test might detect toxin-producing E. coli and other bacteria that can cause HUS

Prognosis

With proper management, most children who develop hemolytic uremic syndrome and its complications recover without permanent damage to their health. However, children with hemolytic uremic syndrome may have serious and sometimes life-threatening complications, including:

• acute kidney injury
• high blood pressure
• blood-clotting problems that can lead to bleeding
• seizures
• heart problems
• chronic, or long lasting, kidney disease
• stroke
• coma

Some children may sustain significant kidney damage that slowly develops into chronic kidney disease (CKD). Children who develop CKD must receive treatment to replace the work the kidneys do, either through dialysis or kidney transplantation

Treatment

HUS requires treatment in the hospital. To ease signs and symptoms and to prevent further problems, treatment might include:

• Fluid replacement. Lost fluid and electrolytes must be carefully replaced because the kidneys aren't removing fluids and waste as efficiently as normal.
• Red blood cell transfusions. Red blood cells, transfused through an intravenous (IV) needle, can help reverse signs and symptoms of HUS including chills, fatigue, shortness of breath, rapid heart rate, yellow skin and dark urine.
• Platelet transfusions. IV transfusions of platelets can help your blood clot more normally if you're bleeding or bruising easily.
• 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.
• 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. But if you have significant kidney damage, you might need long-term dialysis. Your doctor might also recommend follow-up visits to evaluate your kidney function every year for five years.