A 14-year-old boy is evaluated for a 1-week history of fever, abdominal pain, and bloody diarrhea. He reports no recent travel or medication use but did go to a barbeque 1 week ago and ate hamburgers. His medical history is otherwise unremarkable.
On physical examination, temperature is 38.4°C (101.2°F), blood pressure is 150/96 mm Hg, pulse rate is 100/min, and respiration rate is 14/min. He has petechiae on his legs. The abdomen is diffusely tender. The remainder of the examination is normal.
||7.6 g/dL (76 g/L)
||15,000/μL (15 x 109/L)
||46,000/μL (24 x 109/L)
|Blood urea nitrogen
||36 mg/dL (12.8 mmol/L)
||2.8 mg/dL (247.5 mmol/L)
Urinalysis is positive for many erythrocytes per high-power field.
The most appropriate next management step is a peripheral blood smear. This patient likely has hemolytic uremic syndrome (HUS), which is characterized by thrombocytopenia and thrombotic microangiopathy. Thrombotic microangiopathy is a clinical syndrome that affects multiple organ systems but is always characterized by thrombocytopenia and microangiopathic hemolytic anemia (schistocytes on the peripheral blood smear, elevated reticulocyte count, and elevated lactate dehydrogenase level). Thrombotic microangiopathy may manifest as thrombotic thrombocytopenic purpura or HUS. HUS is usually caused by infection with Shiga toxin–producing Escherichia coli (O157:H7), often related to ingestion of contaminated, under-cooked beef, or by complement dysregulation caused by genetic mutations. Additional manifestations of HUS may include acute kidney injury and neurologic findings (for example, headache, confusion) but the only diagnostic criteria are thrombocytopenia and microangiopathic hemolytic anemia in the absence of any other potential cause.
Antibiotics are not recommended in the treatment of HUS. Studies in children have shown either no benefit or increased complications when antibiotics are used. The mainstay of treatment is supportive, with adequate fluids and close monitoring of electrolytes and blood counts; dialysis may be required for acute renal failure. Transfusion of packed red blood cells may be indicated if anemia worsens, but platelet transfusion is controversial, because it may worsen the thrombotic process and is typically used only when bleeding is significant.
Routine stool cultures only test for salmonella, shigella, and campylobacter. Therefore, in patients with bloody diarrhea, stool should also be sent specifically for E. coli O157:H7 testing. Fecal leukocyte testing has poor sensitivity and specificity in the diagnosis of infectious diarrhea, will not specifically diagnose HUS, and will not add useful diagnostic information.
- Hemolytic uremic syndrome diagnosis is based on the presence of microangiopathic hemolytic anemia and thrombocytopenia.