Hemolytic Uremic syndrome

Question 1

Definition of Hemolytic Uremic Syndrome (HUS)

Answer 1

Combination of hemolytic anemia, thrombocytopenia , and acute kidney injury.

Question 2

Causes of Hemolytic Uremic Syndrome (HUS)

Answer 2

The most common cause of HUS in children is an infection with certain strains of Escherichia coli (E. coli) bacteria, particularly a strain called Shiga toxin-producing E. coli (STEC).
The primary cause of HUS in children is infection with STEC, most commonly the serotype O157:H7. This type of E. coli infection is often associated with consuming contaminated food, such as undercooked ground beef, unpasteurized milk, or contaminated fruits and vegetables.
Other less common causes of HUS include other types of bacteria (such as Streptococcus pneumoniae), certain medications (such as chemotherapeutic agents), genetic mutations (such as mutations in complement regulatory proteins), and autoimmune conditions.

Question 3

Pathomechanism of Hemolytic Uremic Syndrome (HUS)

Answer 3

In the case of STEC-associated HUS, the bacteria produce toxins called Shiga toxins. These toxins enter the bloodstream and damage the lining of blood vessels, particularly the small blood vessels in the kidneys. The damaged blood vessels trigger a cascade of events leading to the destruction of red blood cells, platelet activation and consumption, and kidney injury. The exact mechanisms underlying non-STEC-associated HUS may differ depending on the specific cause.
Toxic damage to endothelium leads to intravascular thrombogenesis
■ Consumptive thrombocytopenia
■ Vascular occlusions lead to mechanical RBC damage
■ Decreased blood supply to the kidney leads to low GFR

Question 4

Symptoms of Hemolytic Uremic Syndrome (HUS)

Answer 4

Present with abdominal pain preceded by bloody diarrhea, vomiting, and fever.
Oliguria is an early sign.
Causes pallor, irritability, lethargy.
Neuro symptoms such as seizure/AMS can develop.

○ Most common cause of AKI in children, usually under 5 y/o. Relatively low mortality (3-5%) if diarrhea is present, but type without diarrhea is more severe (25% mortality)

○ HUS with diarrhea (D+): from E.coli O157:H7 or Shigella. Acquired from undercooked meat (especially hamburgers), unpasteurized milk, contact with
farm animals.
Antibiotics and antidiarrheal agents increase likelihood of HUS; avoid them.

○ HUS without diarrhea: from S. pneumoniae, certain drugs and toxins
(cyclosporine, tacrolimus), genetic causes (e.g. vWF deficiency).

Question 5

Diagnosis of Hemolytic Uremic Syndrome (HUS)

Answer 5

Thrombocytopenia, anemia, leukocytosis,.
High LDH
High indirect bilirubin
High Reticulocytes
Negative Coombs test
Check stool cultures
Peripheral blood smear shows schistocytes, Burr cells, helmet cells.
Renal panel : High Bun and High creatinine

Question 6

Treatment of Hemolytic Uremic Syndrome (HUS)

Answer 6

Supportive: fluid/electrolyte management.
Decrease HTN with ACE-inhibitors.
May need RBC transfusion if < 7 g/dL.
Do NOT transfuse platelets unless critically low with active bleeding; platelets can make it worse.

Question 7

Complications of Hemolytic Uremic Syndrome (HUS)

Answer 7

Chronic kidney disease
Hypertension
Acute respiratory distress syndrome (ARDS)
Neurologic complications
Pancreatitis
Heart-related issues.