Hemolytic–uremic syndrome
Hemolytic–uremic syndrome (HUS) is a group of blood disorders characterized by low red blood cells, acute kidney injury (previously called acute renal failure), and low platelets. Initial symptoms typically include bloody diarrhea, fever, vomiting, and weakness. Kidney problems and low platelets then occur as the diarrhea progresses. Children are more commonly affected, but most children recover without permanent damage to their health, although some children may have serious and sometimes life-threatening complications. Adults, especially the elderly, may present a more complicated presentation. Complications may include neurological problems and heart failure.
| Hemolytic–uremic syndrome | |
|---|---|
| Other names | Haemolytic–uraemic syndrome |
| Schistocytes as seen in a person with hemolytic–uremic syndrome | |
| Specialty | Pediatrics, nephrology |
| Symptoms | Early: Bloody diarrhea, vomiting, fever Later: Low platelets, low red blood cells, kidney failure |
| Complications | Neurological problems, heart failure |
| Types | Shiga toxin–producing E. coli HUS (STEC HUS), S. pneumoniae-associated HUS (SP-HUS), Atypical hemolytic uremic syndrome (aHUS), Cobalamin C HUS |
| Causes | Infection by E coli O157:H7, shigella, salmonella |
| Risk factors | Younger age, female, immunocompromised, or existing renal, urinary, or lower GI disease (because these are the systems involved in the disease) |
| Diagnostic method | Blood tests (to monitor levels of platelets, red blood cells, and white blood cells), stool tests (especially to check for microscopic or macroscopic levels of fresh or old blood), urinalysis (to help monitor kidney function, like blood urea nitrogen, or BUN, levels, pH, and for blood in the urine- hematuria) |
| Differential diagnosis | Thrombotic thrombocytopenic purpura (TTP), disseminated intravascular coagulation (DIC), certain problems with an artificial heart valve |
| Treatment | Supportive care, dialysis, steroids, blood transfusions, plasmapheresis |
| Prognosis | <25% long-term kidney problems, which for some of these, could include chronic kidney dysfunction or even failure (which could ultimately need dialysis or transplantation to treat); 5% risk of death during the illness in developed countries with treatment |
| Frequency | 1.5 per 100,000 per year |
| Deaths | <5% risk of death |
Most cases occur after infectious diarrhea due to a specific type of E. coli called O157:H7. Other causes include S. pneumoniae, Shigella, Salmonella, and certain medications. The underlying mechanism typically involves the production of Shiga toxin by the bacteria. Atypical hemolytic uremic syndrome (aHUS) is often due to a genetic mutation and presents differently. However, both can lead to widespread inflammation and multiple blood clots in small blood vessels, a condition known as thrombotic microangiopathy.
Treatment involves supportive care and may include dialysis, steroids, blood transfusions, or plasmapheresis. About 1.5 per 100,000 people are affected per year. Less than 5% of those with the condition die. Of the remainder, up to 25% have ongoing kidney problems. HUS was first defined as a syndrome in 1955.