The most important complication of Kawasaki disease is the development of coronary artery abnormalities. Echocardiography is the investigation of choice to evaluate for aneurysms, myocarditis, valvulitis, thrombus or pericardial effusion. Coronary artery dilation can be observed in up to 50% of untreated patients by the tenth day of illness. Echocardiography can also be useful in diagnosing atypical cases but a normal echo does not exclude Kawasaki disease.
Treatment should not be delayed whilst awaiting imaging, as early intervention gives better outcomes.