Hemolytic Uremic Syndrome in Emergency Medicine Workup

  • Author: Audrey J Tan, DO; Chief Editor: Steven C Dronen, MD, FAAEM   more...
 
Updated: Sep 26, 2011
 

Laboratory Studies

  • Hemolytic uremic syndrome (HUS) is primarily a clinical diagnosis coupled with consistent laboratory findings.
  • Hemolytic uremic syndrome produces a microangiopathic hemolytic anemia with a hemoglobin level that is typically less than 8 g/dL. This is a consistent finding and is necessary to establish the diagnosis.
    • The hallmark of hemolytic uremic syndrome in the peripheral smear is the presence of schistocytes. These consist of fragmented, deformed, irregular, or helmet-shaped RBCs, as shown in the image below. They reflect the partial destruction of RBCs that occurs as they traverse vessels partially occluded by platelet and hyaline microthrombi. The peripheral smear may also contain giant platelets. This is due to the reduced platelet survival time resulting from the peripheral consumption/destruction. Peripheral smear in hemolytic uremic syndrome (HUSPeripheral smear in hemolytic uremic syndrome (HUS), with findings of microangiopathic hemolytic anemia. Note schistocytes/helmet cells as well as decrease in platelets. Image courtesy of Emma Z. Du, MD.
    • A consumptive coagulopathy is typically not present.
  • Thrombocytopenia is noted and is typically mild to moderate in severity with platelet counts of less than 60,000 per mL. In spite of this finding, neither purpura nor active bleeding is typically seen.
  • Prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen are within the reference ranges, thus differentiating hemolytic uremic syndrome and thrombotic thrombocytopenic purpura from disseminated intravascular coagulation (DIC).
  • Elevation of lactate dehydrogenase (LDH) and indirect bilirubin levels reflects intravascular hemolysis. Bilirubin rarely exceeds 2-3 mg/dL. Haptoglobin is very low, as it is consumed by free hemoglobin released by the destroyed RBC’.
  • Blood urea nitrogen (BUN) and creatinine measurements are markedly elevated. However, there is no correlation between the severity of anemia and the severity of the renal disease.
  • Urine, if present, may contain protein and RBCs.
  • D-dimer and fibrinogen levels are usually within the reference range.
  • The reticulocyte count should be elevated.
  • Coombs test results are negative, indicating that the anemia is not immunologically mediated.
  • A moderate leukocytosis may be present but rarely more than 20,000 per mL.
  • Plasma contains free hemoglobin that can often be observed with the naked eye. The degree correlates with the severity of the anemia.
  • Bone marrow reveals erythroid hyperplasia and increased megakaryocytes.
  • Blood cultures are negative in E coli –mediated disease since only the shiga-like toxin is circulating in the blood while the organisms remain in the GI lumen.
  • Stool cultures typically detect shiga toxin-producing E coli.
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Imaging Studies

Imaging studies are not indicated for the diagnosis of hemolytic uremic syndrome unless a viscus perforation is suspected. At that point, plain films or CT will aid in the diagnosis.

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Contributor Information and Disclosures
Author

Audrey J Tan, DO  Staff Physician, Department of Emergency Medicine, State University of New York Downstate Medical Center, Kings County Hospital Center

Audrey J Tan, DO is a member of the following medical societies: American College of Emergency Physicians and American Medical Association

Disclosure: Nothing to disclose.

Coauthor(s)

Mark A Silverberg, MD, MMB, FACEP  Assistant Professor, Associate Residency Director, Department of Emergency Medicine, State University of New York Downstate College of Medicine; Consulting Staff, Department of Emergency Medicine, Staten Island University Hospital, Kings County Hospital, University Hospital, State University of New York Downstate Medical Center

Mark A Silverberg, MD, MMB, FACEP is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, Council of Emergency Medicine Residency Directors, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Specialty Editor Board

William G Gossman, MD  Associate Clinical Professor of Emergency Medicine, Creighton University School of Medicine; Consulting Staff, Department of Emergency Medicine, Creighton University Medical Center

William G Gossman, MD is a member of the following medical societies: American Academy of Emergency Medicine

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Jeffrey L Arnold, MD, FACEP  Chairman, Department of Emergency Medicine, Santa Clara Valley Medical Center

Jeffrey L Arnold, MD, FACEP is a member of the following medical societies: American Academy of Emergency Medicine and American College of Physicians

Disclosure: Nothing to disclose.

John D Halamka, MD, MS  Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center

John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Steven C Dronen, MD, FAAEM  Chair, Department of Emergency Medicine, LeConte Medical Center

Steven C Dronen, MD, FAAEM is a member of the following medical societies: American Academy of Emergency Medicine and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Additional Contributors

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous author, William Shapiro, MD, to the development and writing of this article.

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Peripheral smear in hemolytic uremic syndrome (HUS), with findings of microangiopathic hemolytic anemia. Note schistocytes/helmet cells as well as decrease in platelets. Image courtesy of Emma Z. Du, MD.
 
 
 
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