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Kawasaki Disease: Laboratory Evaluation and Cardiac Imaging

King, Brent R. MD

Pediatric Rounds: Part 2 in a Series

Dr. King is an associate professor of emergency medicine and pediatrics, and the chairman of the department of emergency medicine at the University of Texas Houston Medical School.



Although Kawasaki disease by definition requires a patient to have experienced five days of fever, a recent paper from the American Academy of Pediatrics and the American Heart Association allows us to make the diagnosis on day four provided the child meets other criteria. That's a relief! Who knows how many children with classical Kawasaki disease I might have sent home on day four if not for these recommendations?

Seriously, though, this is a potential problem, and I'm not certain the committee went far enough in its recommendations. Even if the patient comes to the ED on day two or day three but otherwise meets the criteria for Kawasaki disease, I suspect that most of us would at least consider the diagnosis, and at the very least, ensure the child is carefully observed.

Things become much more difficult in babies because they may have Kawasaki disease without manifesting the typical clinical signs. They may, in fact, have only prolonged fever. The diagnosis also is difficult when the child has some but not all of the required diagnostic features, what the authors call “incomplete Kawasaki disease,” to distinguish these children from those who probably have the disease but present atypically. Only the latter group should be said to have atypical Kawasaki disease.

Patients lacking lab criteria might have incomplete Kawasaki disease and should be referred for an echocardiograM

In all of these cases, the diagnosis rests on a combination of laboratory evaluation and cardiac imaging. When evaluating an infant with four or five days of fever without another focus or an older child with five days of fever but only two or three of the diagnostic criteria, the authors suggest that we begin by looking for symptoms and signs associated with Kawasaki disease. I mentioned these in the last column, and the list is long. But I encourage you to find the paper and look at the table, which includes congestive heart failure and other cardiac symptoms, arthritis/arthralgia, diarrhea, vomiting, abdominal pain, aseptic meningitis, and urethritis. The list does not, however, include exudative pharyngitis, oral ulcerations, pneumonia and other pulmonary diseases, vesicular rash, and diffuse adenopathy.

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Lacking Symptoms

For patients who lack associated features or who have additional signs not usually seen in Kawasaki disease, the authors recommend watchful waiting. These patients should be followed closely for additional symptoms. On the other hand, those who have symptoms consistent with Kawasaki disease should undergo further diagnostic testing starting with a C-Reactive Protein (CRP) and an Erythrocyte Sedimentation Rate (ESR). If the CRP is greater than or equal to 3 mg/DL or the ESR is greater than or equal to 40 mm/hr, further testing is warranted. This testing includes a complete blood count, a urinalysis, a serum alanine aminotransferase (ALT) level, and a serum albumin level. Three or more of these results essentially confirm the diagnosis: anemia for age, elevation in serum ALT, albumin less than or equal to 3 g/dL, a white blood cell count of greater than or equal to 15,000, greater than or equal to 10 white blood cells per high-powered field on the urinalysis, or a platelet count of greater than or equal to 450,000, after seven days of symptoms.

Patients who lack at least three of the supplemental laboratory criteria still might have incomplete Kawasaki disease, and they should be referred for an echocardiogram. Because treatment should begin as soon as possible (preferably within 10 days from the onset of fever), the echocardiogram should be performed promptly. And what about those who do not have an elevated CRP or ESR? The authors recommend that these children be evaluated daily for two more days. If the fever has not abated by then, the assessment should start over by first evaluating the patient for new clinical features and then repeating the laboratory testing.

When the diagnosis is confirmed or strongly suspected based on these criteria, treatment is indicated but in most cases can be deferred until the child reaches an inpatient unit. Nonetheless, emergency physicians should have a basic understanding of the treatment protocol. All children should receive aspirin and intravenous immunoglobulin therapy. A clinical trial to ascertain whether treatment with steroids might provide additional benefit is ongoing. Pentoxifylline, a methyl xanthine that specifically inhibits TNF-alpha messenger RNA transcription, reduced the incidence of aneurysms in one small study, but is not yet considered standard therapy.

Because Kawasaki disease remains incompletely understood, there are probably children with atypical presentations who go undiagnosed only to develop acute coronary syndromes later in life. Until we know more about this unusual disease, emergency physicians should keep the diagnosis in mind when treating children with prolonged fever and two or more of the usual clinical signs.

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Suggested Reading:

Newburger JW, et al. Diagnosis, treatment, and long-term management of Kawasaki disease: A statement for health professionals from the Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease, Council on Cardiovascular Disease in the Young, American Heart Association. Pediatrics 2004;114:1708.
© 2006 Lippincott Williams & Wilkins, Inc.