hemolytic-uremic syndrome

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Hemolytic-Uremic Syndrome

 

Definition

Hemolytic-uremic syndrome (HUS) is a rare condition that affects mostly children under the age of 10, but also may affect the elderly as well as persons with other illnesses. HUS, which most commonly develops after a severe bowel infection with certain toxic strains of a bacteria, is characterized by destruction of red blood cells, damage to the lining of blood vessel walls, and in severe cases, kidney failure.

Description

Most cases of HUS occur after an infection in the digestive system that has been caused by toxin-producing strains of the bacterium Escherichia coli. About 75% of HUS cases in the United States are caused by the strain referred to as E. coli O157:H7, which is found in the intestinal tract of cattle, while the remaining cases are caused by non-O157 strains. Some children infected with E. coli O157:H7 will develop HUS. HUS also can follow respiratory infection episodes in young children. In the United States, there are about 20,000 infections and 250 deaths annually that are caused by E. coli O157:H7. HUS has also been known to occur in persons using drugs such as oral contraceptives, immunosuppressors, and antineoplastics, and in women during the postpartum period.
E. coli. O157:H7, first identified in 1982, and isolated with increasing frequency since then, is found in contaminated foods such as meat, dairy products, and juices. Infection with E. coli. O157:H7 causes severe gastroenteritis, which can include abdominal pain, vomiting, and bloody diarrhea. For most children, the vomiting and diarrhea stop within two to three days. However, about 5 to 10% of the children will develop HUS and will become pale, tired, and irritable. Toxins produced by the bacteria enter the blood stream, where they destroy red blood cells and platelets, which contribute to the clotting of blood. The damaged red blood cells and platelets clog tiny blood vessels in the kidneys, or form lesions to occur in the kidneys, making it difficult for the kidneys to remove wastes and extra fluid from the body, resulting in hypertension, fluid accumulation, and reduced production of urine.

Causes and symptoms

The most common way an E. coli O157:H7 infection is contracted is through the consumption of undercooked ground beef (e.g., eating hamburgers that are still pink inside). Healthy cattle carry E. coli within their intestines. During the slaughtering process, the meat can become contaminated with the E. coli from the intestines. When contaminated beef is ground up, the E. coli are spread throughout the meat. Additional ways to contract an E. coli infection include drinking contaminated water and unpasteurized milk and juices, eating contaminated fruits and vegetables, and working with cattle. The infection is also easily transmitted from an infected person to others in settings such as day care centers and nursing homes when improper sanitary practices are used.
Symptoms of an E. coli O157:H7 infection start about seven days after infection with the bacteria. The first symptom is sudden onset of severe abdominal cramps. After a few hours, watery diarrhea starts, causing loss of fluids and electrolytes (dehydration), which causes the person to feel tired and ill. The watery diarrhea lasts for about a day, and then changes to bright red bloody stools, as the infection causes sores to form in the intestines. The bloody diarrhea lasts for two to five days, with as many as ten bowel movements a day. Additional symptoms may include nausea and vomiting, without a fever, or with only a mild fever. After about five to ten days, HUS can develop, which is characterized by paleness, irritability, and fatigue, as well as reduced urine production.

Diagnosis

The diagnosis of an E. 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. If a positive culture is obtained, the patient should be monitored for the development of HUS, with treatment initiated as required.
Children should not go to day care until they have had two negative stool cultures. Older people in nursing homes should stay in bed until two stool cultures are negative.

Treatment

Treatment of HUS is supportive, with particular attention to management of fluids and electrolytes. Treatment generally is provided in a hospital setting. Blood transfusions may be required. In about 50% of the cases, short term replacement of kidney function is required in the form of dialysis. Most patients will recover kidney function and be able to discontinue dialysis.
Some studies have shown that the use of antibiotics and antimotility agents during an E. coli infection may worsen the course of the infection and should be avoided. However, other studies have been less definitive. Physicians should stay informed so that clinical practices matches medical advances on this aspect of treatment.

Alternative treatment

Persons with HUS must be under the care of health care professionals skilled in the treatment of HUS.

Prognosis

Ninety percent of children with HUS who receive careful supportive care survive the initial acute stages of the condition, with most having no long-term effects. However, between 10 and 30 percent of the survivors will have kidney damage that will lead to kidney failure immediately or within several years. These children with kidney failure require on-going dialysis to remove wastes and extra fluids from their bodies, or may require a kidney transplant.

Key terms

Antineoplastics — Agents that inhibit or prevent the development, maturation, and proliferation of malignant cells.
Gastroenteritis — An acute inflammation of the lining of the stomach and intestines, characterized by nausea, diarrhea, abdominal pain and weakness, which has various causes, including food poisoning due to infection with such organisms as Escherichia coli, Staphylococcus aureus and Salmonella species, consumption of irritating food or drink, or psychological factors such as anger, stress and fear.

Prevention

Prevention of HUS caused by ingestion of foods contaminated with E. coli O157:H7 and other toxin-producing bacteria is accomplished through practicing hygienic food preparation techniques, including adequate handwashing, cooking of meat thoroughly, defrosting meats safely, vigorous washing of fruits and vegetables, and handling leftovers properly. Irradiation of meat has been approved by the United States Food and Drug Administration and the United States Department of Agriculture in order to decrease bacterial contamination of consumer meat supplies.

Resources

Other

National Kidney and Urologic Diseases Information Clearinghouse. Fact Sheet: Hemolytic Uremic Syndrome. NIH Publication No. 99-4570. March 2000. 〈http://www.niddk.nih.gov/health/kidney/summary/hus/〉.

hemolytic-uremic syndrome

Internal medicine A condition often accompanied by a prodrome of bloody diarrhea, more common in summer and microangiopathic hemolytic anemia, thrombocytopenia and platelet defects, not uncommon in infants < age 2 Lab Impaired aggregation, depleted platelet serotonin, ADP, β-thromboglobulin. See TTP-HUS.
hemolytic-uremic syndrome etiology
•  Prototypic or 'classic' form
•  Post-infectious, eg Shigella dysenteriae-1, S pneumoniae, Salmonella typhi, occasionally viruses
•  Hereditary forms: AD or AR associated with HTN
•  Immune-mediated forms
•  Associated with other diseases, eg HTN, connective tissue disease, immunosuppression, RT to kidneys
•  Related to pregnancy and oral contraceptives

hemolytic

pertaining to, characterized by, or producing hemolysis.

hemolytic anemia
anemia caused by the increased destruction of erythrocytes which may occur in the vascular system—intravascular hemolysis, or due to phagocytosis by the monocyte-macrophage system—extravascular or intracellular hemolysis. It may result from incompatibility (see alloimmune hemolytic anemia of the newborn), from mismatched blood transfusions, from poisons such as copper, organic agents in plants such as kale, from nutritional deficiencies such as phosphorus and from protozoan infections such as babesiosis. Hemolytic anemia may also occur as a result of a disorder of the immune response in which B cell-produced antibodies fail to recognize erythrocytes that are 'self' and directly attack and destroy them. In addition to the usual signs of anemia, the patient may also exhibit jaundice.
hemolytic component
a degree of extravascular hemolysis in association with other types of anemia.
hemolytic disease of the newborn
see alloimmune hemolytic anemia of the newborn.
hemolytic enterotoxemia
a little reported disease recorded mostly in Australia in sheep, cattle and foals; a highly fatal hemolytic anemia associated with a heavy population of Clostridium perfringens type A in the intestines.
hemolytic plaque assay
see plaque assay.
hemolytic-uremic syndrome
a microangiopathic hemolytic anemia with thrombocytopenia and severe involvement of renal vasculature which leads to acute renal failure. In humans associated with verocytoxin-producing bacteria such as Escherichia coli, Shigella and some Salmonella; usually associated with the ingestion of poorly cooked meat. A similar clinical syndrome has been reported in cows, horses and dogs.