Hemolytic-Uremic Syndrome

Aka: Hemolytic-Uremic Syndrome, Hemolytic Uremic Syndrome

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II. Epidemiology

  1. Age: Children ages 1 to 10 years old most commonly affected
    1. Contrast with Thrombotic Thrombocytopenic Purpura which is seen primarily in adults
  2. Incidence: 1-3 per 100,000
  3. Peak timing: June to September in United States

III. Pathophysiology

  1. Shiga-Toxin Producing Escherichia coli in 90% of cases (e.g. 0157:H7, STEC)
    1. See Diarrhea-positive Hemolytic Uremic Syndrome below
    2. Other uncommon causes include Shigella dysenteriae, Streptococcus Pneumoniae, HIV Infection, and Influenza
    3. Proinflammatory factors (IL-8, TNFa)
    4. Prothombotic Changes
      1. Fibrin deposited in renal microvasculature
    5. Verocytotoxin induces endothelial injury
      1. Red Blood Cell destruction
      2. Platelet destruction, consumption, sequestration
      3. Platelet thrombus formation
  2. Classic triad (follows Abdominal Pain and Diarrhea)
    1. Microangiopathic Hemolytic Anemia
    2. Acute Renal Failure
    3. Thrombocytopenia
  3. Predictors of HUS development (3-15% of STEC Diarrhea)
    1. Very young or elderly
    2. Close contact with farm animals
    3. Bloody Diarrhea
    4. Fever
    5. Increased White Blood Cell Count
    6. Increased C-Reactive Protein
    7. Early use of antibiotics in STEC Diarrhea
      1. Results in prolonged intestinal exposure to toxin

IV. Types

  1. Diarrhea-positive Hemolytic Uremic Syndrome
    1. Related to Shiga-toxin producing Escherichia coli
  2. Diarrhea-negative Hemolytic Uremic Syndrome
    1. Sporadic in adults
    2. Consider Thrombotic Thrombocytopenic Purpura

V. Risk Factors

  1. Familial risk (Factor H Deficiency)
  2. Precipitating Infection
    1. Escherichia coli
    2. Streptococcus Pneumoniae
  3. Predisposing Medications
    1. Cyclosporine
    2. Tacrolimus
    3. Radiation Therapy
  4. Predisposing Conditions
    1. Pregnancy
    2. Systemic Lupus Erythematosus
    3. Glomerulonephritis
    4. Cancer
  5. Escherichia coli 0157:H7 (Shiga-Toxin) exposures
    1. Vegetables: Alfalfa/radish sprouts, leaf lettuce
    2. Undercooked Meats: Deer, Ground beef, sausage, deli
    3. Unpasteurized drinks: Apple juice, Milks
    4. Contaminated lakes or municipal water supplies
    5. Petting farm animals

VI. Symptoms (symptomatic in all children)

  1. Follows 3-4 day Incubation Period of E. coli 0157:H7
  2. Diarrhea
    1. Bloody Diarrhea (precedes HUS by 3-14 days)
    2. Non-bloody in some cases
  3. Abdominal cramping
  4. Nausea or Vomiting
  5. Low-grade fever
  6. Petechiae and Purpura are rarely present
    1. Contrast with Thrombotic Thrombocytopenic Purpura

VII. Diagnosis

  1. Hemolysis
  2. Thrombocytopenia

VIII. Labs

  1. Complete Blood Count with Platelets
    1. Anemia with Hemoglobin 8-9 g/dl due to Hemolysis
    2. Thromboctopenia (Platelet Count <150,000)
    3. Leukocytosis
  2. Peripheral Smear
    1. Hemolysis (Burr cells, helmet cells)
  3. Stool Culture
    1. Escherichia coli 0157:H7 variably positive
    2. May have resolved by the time HUS presents
  4. Renal Function Tests
    1. Blood Urea Nitrogen increased
    2. Serum Creatinine increased
  5. Urinalysis
    1. Hematuria
    2. Proteinuria
  6. Other findings
    1. Increased Lactate Dehydrogenase
    2. Coombs negative
    3. Reticulocyte Count increased
    4. Decreased Haptoglobin

IX. Differential Diagnosis

  1. Thrombotic Thrombocytopenic Purpura
    1. Occurs more often in adults
    2. Neurologic sequelae more common than renal
    3. Bloody Diarrhea typically absent
  2. Appendicitis
  3. Inflammatory Bowel Disease
  4. Intussusception
  5. Systemic Lupus Erythematosus
  6. Disseminated Intravascular Coagulation
  7. Acute Gastroenteritis

X. Management

  1. Despite similarity to TTP, treatment is different
  2. Supportive Care
    1. Fluid and Electrolyte management
      1. Hydration prior to HUS decreases Renal Failure
    2. Monitor Hemoglobin, Hematocrit and Platelets
      1. Transfuse Red Blood Cells to keep Hemoglobin >6-7
      2. Platelet Transfusions are controversial
        1. May risk thrombosis
    3. Hemodialysis if Renal Failure occurs
  3. Ineffective or proovcative treatments to avoid
    1. Antibiotics are to be avoided
      1. Worsen complication rate
      2. Increase risk of HUS in STEC Diarrhea
    2. Plasmaphoresis
    3. Anti-thrombotic agents
    4. Corticosteroids
    5. Shiga toxin-binding agents

XI. Complications

  1. Gastrointestinal complications
    1. Rectal Prolapse and colitis (10% of cases)
    2. Intussusception
    3. Pancreatitis
    4. Intestinal perforation
  2. Neurologic complications (10%, higher mortality risk)
    1. Altered Mental Status (e.g. coma)
    2. Cerebrovascular Accident
    3. Seizure Disorder
  3. Renal complications
    1. Chronic Renal Failure (25% risk, 3% risk of ESRD)
    2. Hypertension

XII. Prognosis

  1. Hospital stay: 11 days on average
  2. Survival: 90-95%

XIII. References

  1. Merrill and Gillen (2016) Crit Dec Emerg Med 30(3): 3-8
  2. Baker (2000) Curr Opin Pediatr 12(1):23-8 [PubMed]
  3. Kakishita (2000) Int J Hematol 71(4):320-7 [PubMed]
  4. Razzaq (2006) Am Fam Physician 74:991-8 [PubMed]
  5. Robson (2000) Paediatr Drugs 2(4):243-52 [PubMed]
  6. Thorpe (2004) Clin Infect Dis 38:1298-303 [PubMed]
  7. Trachtman (1999) Curr Opin Pediatr 11(2):162-8 [PubMed]

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