Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sogand Goudarzi, MD [2] Anila Hussain, MD [3] OverviewIn medicine, hemolytic-uremic syndrome (or haemolytic-uraemic syndrome, abbreviated HUS) is a disease characterized by microangiopathic hemolytic anemia, acute renal failure and a low platelet count (thrombocytopenia). It is due to the abnormal blood clotting within the capillaries leading to RBC shearing and destruction while passing through clogged capillaries and obstruction of kidney filtration system by damaged RBC's lead to acute kidney injury and is one of the leading causes of acute renal failure in children. The two main types are typical and atypical Hemolytic uremic syndrome(HUS). Typical HUS is caused following a diarrheal infection by E.coli OH157: H7 and is responsible for 90 percent of HUS cases in Children. Atypical HUS is not associated with gastrointestinal symptoms and also has a less favorable outcome. Historical PerspectiveIn 1955, Gasser et al first described hemolytic-uremic syndrome (HUS). There have been several outbreaks of HUS all over the world over past years. ClassificationHUS may be classified as typical (Caused by Shiga-toxin producing E.coli/ Shigella Infection) or atypical (caused by complement factor abnormalities, other viral or bacterial infections, HIV, malignancy, organ transplantation, and rarely SLE and pregnancy related). PathophysiologyIt is understood that hemolytic uremic syndrome is the result of microvascular endothelial cell damage characterized by thrombotic microangiopathy (TMA) in renal glomeruli, gastrointestinal tract, brain and pancreas in all of which the main lesion is the thickening of vessel wall (mainly in capillaries and arterioles), microthrombi in platelets and obstruction of vessel lumen( partial or complete). Loss of physiological resistance to thrombus formation, complement consumption, leukocyte adhesion to damaged endothelium, the abnormal release of Von Willibrand Factor (vWF) and fragmentation, and increased vascular shear stress lead to further amplification of microangiopathy. Typical/ Shiga-toxin-associated hemolytic uremic syndrome (HUS) is usually caused by E.Coli and serotype O157: H7 is most common while congenital predisposing conditions like complement factor abnormalities may play a role in recurrent and familial forms[1]. CausesCommon causes of HUS may include:[2][3][4][5]
Less common causes include:
Differentiating [Disease] from Other DiseasesEpidemiology and DemographicsThe highest proportion of HUS cases (15.3%) occurred among children aged <5 years. HUS affects female more than male and white race more than other races. Mortality is more commonly seen in elderly patients in which disease is less common but more dangerous Risk FactorsThe most potent risk factor in the development of Hemolytic Uremic Syndrome in childhood is infection with Verocytotoxin (Shiga-like toxin)-producing bacteria, usually Enterohemorrhagic Escherichia coli (VTEC/STEC),and in some tropical regions Shigella dysenteriae type I[6] . Other risk factors include genetic mutations in Complement factors, Pneumococcal infections, autoimmune diseases like SLE and antiphospholipid Syndrome, pregnancy, antineoplastic and immunosuppressive drugs, HIV infection and organ transplantation. ScreeningThere is insufficient evidence to recommend screening for Hemolytic-Uremic Syndrome Natural History, Complications, and Prognosis5 percent of patients with EHEC or Shiga toxin-producing E.coli infection will develop HUS presenting with bloody diarrhea, nausea, vomiting, and decreased urination. Common complications of HUS include renal failure which can be acute (AKI) or develop over time(chronic renal failure), hypertension, neurological problems like stroke, seizure, coma and eventually death. Prognosis depends on the associated complications and about 12% of patients with diarrhea-associated HUS progress to end-stage renal failure within 4 years and about 25% have long-term renal impairment leading to 9% renal transplants in children and adolescents. DiagnosisHistory and SymptomsIt usually starts with gastrointestinal prodrome including bloody diarrhea and fever that may occur 2-7 days before the onset of renal failure. Other symptoms include nausea, vomiting, abdominal pain and swelling, decreased urination, fatigue, irritability, and swelling of the body. Physical ExaminationCommon physical examination findings of Hemolytic Uremic Syndrome include edema and fluid overload, high blood pressure and often severe pallor. Gastrointestinal findings may include abdominal tenderness, distension and guarding. Bruising, purpura, petechiae or oozing from the site of venipuncture may b seen sometimes. Laboratory FindingsThe classic laboratory findings in HUS include anemia, thrombocytopenia, and acute renal damage. Anemia is microangiopathic hemolytic anemia which low hemoglobin often < 8g/dl, high reticulocyte count and LDH, low Haptoglobin level as well as fragmented RBC's and Schistiocytes on the peripheral blood smear. Platelets are frequently less than 60,000 without active bleeding usually and renal damage is seen in form of high creatinine, BUN, and electrolyte abnormalities. Imaging FindingsX-ray: The classic laboratory findings in HUS include anemia, thrombocytopenia, and acute renal damage. Anemia is microangiopathic hemolytic anemia which low hemoglobin often < 8g/dl, high reticulocyte count and LDH, low Haptoglobin level as well as fragmented RBC's and Schistiocytes on the peripheral blood smear. Platelets are frequently less than 60,000 without active bleeding usually and renal damage is seen in form of high creatinine, BUN, and electrolyte abnormalities. USG abdomen: Abdominal ultrasound findings seen in HUS may include Increased parenchymal density/echogenicity in kidneys, hepatomegaly, splenomegaly, ascites, and pleural effusions. MRI Brain: BrainMRI may be helpful in the diagnosis of pathological changes in patients with CNS manifestations/ complications like seizures, AMS, visual changes or others in patients of HUS. Findings on MRI may include basal ganglia, brainstem, cerebellar or thalamic lesions. Other Diagnostic StudiesOther important diagnostic tests include
TreatmentMedical Therapy
Surgery
PreventionReferences
Template:WH Template:WS What are the 5 symptoms of hemolytic uremic syndrome?What are the symptoms of hemolytic uremic syndrome? Symptoms of HUS include vomiting, bloody diarrhea (loose stool/poop), stomach pain, fever, chills, and headache. As infection progresses, persons may experience fatigue, weakness, fainting, bruising, and paleness.
What are the features of HUS?Easy bruising or unexplained bruises. Unusual bleeding, such as bleeding from the nose and mouth. Decreased urination or blood in the urine. Swelling (edema) of the legs, feet or ankles, and less often in the face, hands, feet or entire body.
What does it mean if a patient has hemolytic uremic syndrome HUS )?Hemolytic uremic syndrome (HUS) is a condition that affects the blood and blood vessels. It results in: the destruction of blood platelets (cells involved in clotting) a low red blood cell count (anemia) kidney failure due to damage to the tiny blood vessels of the kidneys.
Which findings indicate hemolytic uremic syndrome?The characteristic pathologic findings of hemolytic-uremic syndrome (HUS) are occlusive lesions of the arterioles and small arteries and consequent tissue microinfarctions. In HUS, the lesions are usually limited to the kidneys, whereas the lesions are more widespread in thrombotic thrombocytopenic purpura (TTP).
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