Hemolytic-Uremic Syndrome Workup

Updated: Nov 16, 2017
  • Author: Malvinder S Parmar, MBBS, MS, FRCPC, FACP, FASN; Chief Editor: Srikanth Nagalla, MBBS, MS, FACP  more...
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Workup

Laboratory Studies

Laboratory studies for hemolytic-uremic syndrome (HUS) may include the following:

  • Urinalysis: Benign mild proteinuria is frequently present; red blood cells (RBCs) and RBC casts may be present

  • Measurement of blood urea nitrogen (BUN), serum creatinine, and serum electrolyte levels

  • Hematologic determination: Severe anemia may be present. Perform peripheral smear for schistocytes (count >1% or two or more schistocytes in a 100× magnification field strongly suggests microangiopathic hemolysis). [21] The degree of thrombocytopenia does not correlate with the severity or the length of illness in HUS. The platelet count usually returns to normal within 2 weeks. Determine activated partial thromboplastin time (aPTT), fibrinogen degradation product (FDP), and D-dimer values.

  • Hemolytic workup: Results may show anemia. Bilirubin levels may be elevated. Lactate dehydrogenase (LDH) levels may be elevated. Haptoglobin levels may be decreased.

  • Stool culture: Obtain a sample for stool culture. Evaluate especially for E coli 0157:H7 and Shigella bacteria.

  • ADAMTS-13 activity: ADAMTS-13 activity is often severely deficient (<10% of normal) in patients with classic thrombotic thrombocytopenic purpura (TTP), but can be seen in patients with severe sepsis (especially in association with disseminated intravascular coagulation or multiorgan failure) and in patients with severe liver disease.

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Imaging Studies

Perform renal ultrasonography in patients with renal failure to rule out obstruction.

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Procedures

Biopsy findings pathologically establish the diagnosis of hemolytic-uremic syndrome (HUS). However, kidney biopsy is not required in children. In adults, kidney biopsy is rarely required.

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Histologic Findings

The characteristic pathologic findings of hemolytic-uremic syndrome (HUS) are occlusive lesions of the arterioles and small arteries and consequent tissue microinfarctions. In HUS, the lesions are usually limited to the kidneys, whereas the lesions are more widespread in thrombotic thrombocytopenic purpura (TTP). Renal lesions are primarily focal and involve both the glomerular capillaries and the afferent arterioles. The venous side of the circulation is usually spared.

A fully developed vascular lesion consists of amorphous-appearing, hyalinelike, thrombi-containing platelet aggregates and a small amount of fibrin that partially or fully occludes the involved small vessels (see images below). Despite extensive arterial changes, no perivascular cellular infiltration or evidence of associated vasculitis is present. Subendothelial deposits with overlying endothelial proliferation may be present.

Photomicrograph (hematoxylin and eosin, original m Photomicrograph (hematoxylin and eosin, original magnification ×25) shows diffuse thickening of the glomerular capillary wall with double contouring (arrow) and swelling of endothelial cells. Fibrin thrombi and packed red blood cells are visible in the lumina (arrowhead). Courtesy of Madeleine Moussa, MD, FRCPC, Department of Pathology, London Health Sciences Centre, London, Ontario, Canada.
Photomicrograph (periodic acid-Schiff, original ma Photomicrograph (periodic acid-Schiff, original magnification ×40) shows diffuse thickening of the glomerular capillary wall with double contouring (arrow) and swelling of endothelial cells. Courtesy of Madeleine Moussa, MD, FRCPC, Department of Pathology, London Health Sciences Centre, London, Ontario, Canada.

As a rule, changes in renal function and the course of renal failure are well correlated with the pathologic findings in the kidney. Obliterative arteriolar lesions are correlated with hypertension and progressive loss of renal function. Glomerular thrombotic microangiopathic lesions and cortical necrosis are the most frequent histologic findings in Stx-HUS, whereas arterial thrombotic microangiopathic lesions are the most frequent features in non – Stx-HUS.

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