Hemolytic uremic syndrome (HUS) is a blood disorder caused by a toxin of Escherichia coli bacterium that affects mostly children under the age of 5.
The hemolytic uremic syndrome is denoted by the destruction of red blood cells, damage to the lining of blood vessel walls, and in severe cases, kidney failure.
Clinically is characterized by the triad of non-immune microangiopathic hemolytic anemia (destruction of red blood cells), thrombocytopenia (a low number of platelets) and acute renal failure.
Hemolytic uremic syndrome usually occurs after an infection in the digestive system caused by a toxin produced by Escherichia coli serotype O157:H7.
The bacteria produce a Shiga toxin (verotoxin) generating an inflammatory response. It causes the formation of clots in the small blood vessels and the RBCs (red blood cells) to break down. The clots clog the filtering system in the kidneys and lead to kidney failure.
The E. coli bacteria is usually transmitted through the consumption of contaminated food, such as undercooked ground beef (for example eating undercooked hamburgers) and other cattle products.
Additional ways to contract the infection include eating contaminated fruits and vegetables, drinking contaminated water and unpasteurized juices and dairy products or from an infected person to others in day care centers or nursing homes.
More than 90% of the cases are due to Escherichia coli, but other infectious agents may cause HUS in children and adults, such as other bacterial pathogen (Shigella dysenteriae), viruses, genetic conditions or some drugs.
Hemolytic uremic syndrome is a disease primarily of infancy and early childhood, generally occurring in children under 10 years old. It may affect also elderly people or people suffering from other diseases.
Hemolytic uremic syndrome occurs with an average annual incidence of 1–3 cases per 100,000 children.
The incubation period for E. coli O157:H7 is usually three to four days; however, the incubation also can range from just one day to eight days.
Symptoms usually begin with abdominal cramps and watery diarrhea. The watery diarrhea lasts for about a day and may cause dehydration. Then, the diarrhea becomes bloody with bright red stools. The bloody diarrhea lasts for two to five days, with as many as ten bowel movements a day.
Additional symptoms may include:
The diagnosis of an Escherichia coli infection is made through a stool culture. The culture must be taken within the first 48 hours after the start of the bloody diarrhea.
Children should not go to day care until they have had two negative stool cultures. Elderly people in nursing homes should stay in bed until two stool cultures are negative.
Because hemolytic uremic syndrome has a wide spectrum of presentation, supportive therapy and close monitoring of fluid and electrolyte status are crucial for a good outcome.
Treatment generally is provided in a hospital and may include:
The use of antibiotics or antimotility drugs may worsen the course of the infection and should be avoided.
The 90% of children who receive treatment in the initial stages of the disease recover with no long-term effects.
The other 10% will have kidney damage that will lead to kidney failure immediately or within several years. These children may require on-going dialysis or a kidney transplant in the future.