Learning objectives

• Describe the etiology of hemolytic uremic syndrome
• Management of hemolytic uremic syndrome

Definition and mechanisms

• Hemolytic uremic syndrome (HUS) is a triad of renal failure, hemolytic anemia, and thrombocytopenia and is the most common cause of renal failure in infancy and childhood
• HUS can lead to widespread inflammation and thrombotic microangiopathy, the formation of platelet microthrombi in the walls of small blood vessels
• Most cases occur after infectious diarrhea due to a specific type of E. coli 
• Other causes include S. pneumonia, Shigella, Salmonella, and certain medications
• Two predominant types:
  • Typical HUS
    • Preceded by 4-6 days of diarrhea
    • Most commonly caused by infection with Shiga toxin-producing E. coli (O157:H7)
    • The mortality rate is 3%-5%
    • Approximately two-thirds of children require dialysis although 85% regain normal renal function
  • Atypical HUS
    • 60-50% can be attributed to dysregulation of the alternative complement pathway
    • Involves mutations in factor H, factor I, CD46/MCP, factor B, and C3 components
    • A mortality rate of up to 25% in the acute phase
    • 50% of patients require renal replacement therapy at some point
• The first symptoms of infection can emerge between 1 to 10 days later, but usually after 3 to 4 days
• Affects about 1.5 per 100,000 people each year
• A multisystemic disease affecting:

Signs and symptoms

• Abdominal pain, cramping, or bloating
• Bloody diarrhea
• Fever
• Vomiting
• Pale coloring, including loss of pink color in cheeks and inside the lower eyelids
• Extreme fatigue
• Shortness of breath
• Easy bruising or unexplained bruises
• Unusual bleeding
• Decreased urination or blood in the urine
• Edema
• Confusion, seizures, or stroke
• High blood pressure
• Low platelets

Complications

• Kidney failure
• Hypertension
• Stroke or seizures
• Coma
• Clotting problems
• Heart problems
• Digestive tract problems

Diagnosis

• Travel and dietary history
• Complete blood count: anemia (Hb < 10 g/dl) and thrombocytopenia
• Comprehensive metabolic panel (elevated creatinine, elevated indirect bilirubin, and elevated lactate dehydrogenase)
• Urinalysis
• Peripheral smear

Treatment

• Fluid resuscitation
• Treat hyperkalemia
• Dialysis
• Control hypertension with standard antihypertensive agents
• Steroids
• Blood transfusion
• Plasmapheresis

Management

Suggested reading

• Pollard BJ, Kitchen, G. Handbook of Clinical Anaesthesia. Fourth Edition. CRC Press. 2018. 978-1-4987-6289-2.
• Noris M, Remuzzi G. Hemolytic uremic syndrome. J Am Soc Nephrol. 2005;16(4):1035-1050.