Question

Diarrhea-related hemolytic uremic syndrome is characterized by all of the following, EXCEPT

• A. Acute renal failure
• B. Coombs' positive hemolytic anemia
• C. Thrombocytopenia
• D. Neutrophilic leukocytosis

Hint:

Ask whether the red cell breakdown in HUS is antibody driven or purely mechanical.

Answer 1

The Correct Option is B

Step 1: Understanding the Question.
The question wants the one finding that is NOT part of diarrhea associated hemolytic uremic syndrome (HUS), the type that follows infection with Shiga toxin producing E. coli.

Step 2: Key Concept.
HUS has a classic triad: microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. A neutrophilic leukocytosis is also a common lab finding during the acute illness. The red cells break down because they get sheared while passing through small vessels blocked with platelet and fibrin clots. This is a mechanical injury, not an antibody attack.

Step 3: Detailed Explanation.
Option (A), acute renal failure, is a core part of HUS. The tiny clots block the glomerular capillaries and cut down kidney function.
Option (B), Coombs' positive hemolytic anemia, does not fit. The direct Coombs test looks for antibody stuck on the red cell surface, which is what happens in autoimmune hemolytic anemia. In HUS the red cells are torn apart by physical shearing, so the Coombs test stays negative.
Option (C), thrombocytopenia, happens because platelets get used up forming the small clots in damaged vessels. It is part of the triad.
Option (D), neutrophilic leukocytosis, is commonly seen during the acute phase of the illness.

Step 4: Final Answer.
The feature that does not belong is Coombs' positive hemolytic anemia, since HUS causes a Coombs negative, microangiopathic hemolysis. \[ \boxed{\text{Coombs' positive hemolytic anemia}} \]