Hemolytic-uremic syndrome

Overview

Hemolytic-uremic syndrome (HUS) is a serious medical condition that primarily affects the blood and kidneys. It is characterized by a triad of symptoms: microangiopathic hemolytic anemia, thrombocytopenia (low platelet count), and acute kidney injury. HUS is most commonly seen in children and often follows a gastrointestinal infection caused by certain strains of Escherichia coli (E. coli), particularly E. coli O157:H7. While many cases resolve with supportive care, severe or untreated cases can lead to life-threatening complications.

Causes

The most common cause of HUS is an infection with Shiga toxin-producing E. coli (STEC), which leads to damage of the small blood vessels, especially in the kidneys. Other, less common causes include:

• Infections: Shigella and other bacterial infections producing similar toxins

• Atypical HUS (aHUS): Caused by genetic mutations affecting the complement system

• Medications: Certain chemotherapy agents or immunosuppressants

• Autoimmune diseases: Such as systemic lupus erythematosus

• Pregnancy: Rarely, HUS can occur in the postpartum period

In most pediatric cases, HUS is associated with STEC infections acquired through contaminated food or water.

Symptoms

Symptoms of HUS typically begin a few days after a diarrheal illness, particularly bloody diarrhea. The main symptoms include:

• Gastrointestinal symptoms: Abdominal pain, vomiting, and bloody diarrhea (especially in STEC-HUS)

• Hemolytic anemia: Fatigue, pallor, and rapid heart rate due to red blood cell destruction

• Thrombocytopenia: Easy bruising, petechiae, and prolonged bleeding

• Acute kidney injury: Decreased urine output, swelling (edema), and high blood pressure

• Neurological symptoms: Irritability, confusion, or seizures in severe cases

The onset is often sudden and progresses quickly, requiring immediate medical attention.

Diagnosis

Diagnosis of hemolytic-uremic syndrome involves clinical evaluation, history of recent diarrheal illness, and laboratory tests. Key investigations include:

• Complete blood count (CBC): Shows anemia and low platelet count

• Peripheral blood smear: Reveals fragmented red blood cells (schistocytes)

• Kidney function tests: Elevated blood urea nitrogen (BUN) and creatinine

• Urinalysis: May show proteinuria, hematuria, and reduced output

• Stool culture: Detects E. coli O157:H7 or Shiga toxin

• Complement studies and genetic testing: For atypical HUS or recurrent cases

Early diagnosis is critical to prevent complications and begin supportive care promptly.

Treatment

Treatment for HUS depends on the severity and underlying cause. Supportive care is the cornerstone of management, particularly in typical (STEC-related) cases. Treatment options include:

• Hospitalization: Required for close monitoring and supportive care

• Intravenous fluids: To maintain hydration and kidney perfusion

• Blood transfusions: For severe anemia or low platelet counts

• Dialysis: Temporary support for kidney function in severe cases

• Antibiotics: Generally avoided in STEC-HUS, as they may increase toxin release

• Eculizumab: A monoclonal antibody used in atypical HUS to inhibit complement activation

Early treatment significantly improves outcomes, especially when complications are promptly managed.

Prognosis

The prognosis of HUS depends on the type and severity of the condition. In typical, STEC-associated HUS, especially in children - the prognosis is generally good with appropriate supportive care, and most patients recover fully. However, complications such as chronic kidney disease, hypertension, and neurological deficits can occur in some cases. Atypical HUS carries a higher risk of recurrence and long-term kidney damage, requiring ongoing follow-up and, in some cases, lifelong therapy. Early diagnosis and multidisciplinary care are key to improving long-term outcomes.