Pediatric Hemolytic Uremic Syndrome Clinical Presentation

Updated: Nov 12, 2018
  • Author: Robert S Gillespie, MD, MPH; Chief Editor: Craig B Langman, MD  more...
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Presentation

History

Patients with Shiga toxin–producing E coli hemolytic-uremic syndrome (STEC-HUS) experience several days of diarrhea, with or without vomiting, followed by sudden onset of symptoms such as irritability and pallor. In more than 80% of patients, the diarrhea is visibly bloody. Other symptoms include restlessness, oliguria, edema, and macroscopic hematuria. In some patients, the prodrome may improve as hemolytic-uremic syndrome symptoms begin. The clinical picture may mimic that of an acute abdomen. In patients infected with a Shiga toxin (Stx)–producing strain of E coli, hemolytic-uremic syndrome occurs in 5-15%.

The risk of progression to hemolytic-uremic syndrome is increased in very young or elderly persons, in patients who have been treated with antimotility drugs or antibiotics, and in patients with a fever or a high leukocyte count.

The history should include inquiry about possible recent exposure to E coli, such as consuming undercooked meat, encounters with livestock or petting zoos, contacts with other persons with diarrhea, and attendance at daycare or school. However, most cases of STEC-HUS are sporadic, with no clearly identifiable source of infection, even when stool culture yields a toxigenic organism. Outbreaks involving multiple persons more commonly lead to a source.

Atypical hemolytic-uremic syndrome (aHUS) may follow a respiratory illness, especially when caused by S pneumoniae.

Features of all forms of hemolytic-uremic syndrome include the following:

  • Hematology: Hemolysis occurs in all patients with hemolytic-uremic syndrome. It can proceed rapidly, resulting in a rapid fall of the hematocrit. Platelet counts usually fall below 40,000/µL. However, the degree of thrombocytopenia does not correlate with the severity of hemolytic-uremic syndrome, and some children can maintain relatively normal kidney function despite severe hematologic abnormalities. Many patients have petechiae, purpura, and oozing from venipuncture sites. Overt bleeding is less common.

  • CNS: Patients often present with sudden onset of lethargy and irritability. Other findings may include ataxia, coma, seizures, cerebral swelling, hemiparesis, and other focal neurologic signs. CNS changes may be caused by cerebral ischemia from microthrombi, effects of hypertension, hyponatremia, or uremia. aHUS tends to be associated with a greater number of neurologic symptoms than STEC-HUS.

  • Renal system: Acute renal insufficiency usually begins with the onset of hemolysis. Although patients have decreased urine output, frequent diffuse watery stools may mask this sign. If renal insufficiency is not recognized and treated, hyponatremia, hyperkalemia, severe acidosis, ascites, edema, pulmonary edema, and hypertension ensue.

  • GI tract: STEC-HUS is usually preceded by 3-12 days of watery or bloody diarrhea. Vomiting and crampy abdominal pain are also common. Note that diarrhea may improve as the other hemolytic-uremic syndrome symptoms begin (eg, thrombocytopenia, renal insufficiency). Life-threatening complications include intestinal perforation or necrosis. Even without these complications, the colitis of hemolytic-uremic syndrome may cause severe abdominal pain, which may persist for several days into the illness.

  • Infectious signs: Fever is present in 5-20% of patients. The presence of fever, leukocytosis, or both is a prognostic indicator of the risk of developing more severe hemolytic-uremic syndrome.

  • Pancreas: Mild pancreatic involvement is common but can be severe on occasion, with necrosis, pseudocysts, or both, which can leave the patient with type 1 diabetes and, on rare occasion, exocrine dysfunction.

  • Cardiovascular: Congestive heart failure may occur.

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Physical

Blood pressure may be elevated unless the patient is volume depleted (eg, from diarrhea). The child appears ill and pale. Abdominal pain and tenderness may be present, possibly severe. Peripheral edema may be present. Petechiae, purpura, or oozing from venipuncture sites may be present.

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Causes

STEC-HUS

GI tract infection with Stx–producing E coli (STEC) precedes most cases of STEC-HUS. Stx1 is identical to the Stx produced by Shigella dysenteriae. Stx2 has a 55-60% amino acid homology with Stx. They injure the gut and lead to hemorrhagic colitis. Most cases worldwide are associated with STEC 0157:H7 infection. This organism is very resilient; viable bacteria have been reported in environments up to 10 months following initial contamination. Aside from Stx production, this bacteria produces virulence factors that mediate tight adherence to the host cell, facilitating transluminal transport of the toxins into the systemic circulation. Cattle are the major reservoir for human infection. The use of antimotility agents, antidiarrheal agents, and antibiotics has been reported to increase the risk of developing hemolytic-uremic syndrome. E coli O104:H4 was responsible for a large outbreak of hemolytic-uremic syndrome in Germany.

Other causes of hemolytic-uremic syndrome include infection by the following:

  • S dysenteriae (established as an etiologic agent)

  • Salmonella typhi (established as an etiologic agent)

  • Campylobacter jejuni (established as an etiologic agent)

  • Bacteroides species

  • Entamoeba histolytica

  • Aeromonas hydrophilia

  • Organisms of the class Microtatobiotes

aHUS

Causes of aHUS include the following:

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