Hemolytic Uremic Syndrome in a Female Toddler

A 2-year-old girl who has had diarrhea and vomiting for about 5 days was brought back to the emergency department for a second visit by her father because he was told that if the frequency of the child’s urination decreased, it could signal severe dehydration. The child has not had any significant pain but did have a low-grade fever and some blood in the stool earlier in the illness, both of which resolved about two days ago. The vomiting has also resolved.

Physical examination: Vital signs are normal except for mild tachycardia. Mucous membranes are moist. The abdomen is soft and non-tender. A rectal exam is deferred. Her skin appears a bit pale. The rest of the physical exam is normal.

Testing     Blood chemistry results:  

Sodium              120 mEq/L

Bicarbonate         18 mEq/L

BUN                    102 mg/dL

Creatinine             4.4 mg/dL 

CBC                      platelets 42 x 10⁹/L;  Hgb 9.2 g/dL

WBC                     normal but smear shows both schistocytes and burr cells

What do you think is causing these crazy lab results?

Answer: Hemolytic uremic syndrome (HUS)

Hemolytic uremic syndrome (HUS) is a rare condition that has multiple similarities to thrombotic thrombocytopenic purpura (TTP), but typically occurs only in children, whereas TTP occurs primarily in adults. HUS is a form of microangiopathic hemolytic anemia (MAHA) and is the number-one cause of renal failure in children.

The classic clinical presentation includes a gastroenteritis that often becomes bloody before eventually improving spontaneously. Around the time of initial clinical improvement, the child develops a hemolytic anemia associated with acute renal failure. Clinical findings can include lethargy, pallor, tachycardia, volume overload, oliguria and/or hematuria.

Testing usually reveals thrombocytopenia and hemolytic anemia that result in a drop in hemoglobin and a rise in bilirubin and lactate dehydrongenase. Schistocytes should be present on the smear. Renal failure causes a rise in both BUN and creatinine and often a dilutional hyponatremia as well. Coagulation parameters should all be within normal limits

Treatment of HUS is primarily supportive, at least initially in the hospital. Dialysis is required in the majority of patients acutely (~80%) and about 15% chronically. RBC transfusion may also be required, but platelets should not be transfused unless there is clinically significant ongoing bleeding.

Excerpt on HEMOLYTIC UREMIC SYNDROME (HUS) from The Emergency Medicine 1-Minute Consult pocketbook

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