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Imaging Diagnosis

Acute Chagas' Disease

In the acute phase ultrasonography may help in detecting enlarged regional or disseminated lymph node involvement and occasionally may show in patients with hepatosplenomegaly a hyperechoic liver due to fatty infiltration. No focal lesions are detected in the liver or spleen.

The heart changes are very well seen in echocardiograms that display to advantage anatomical and functional alterations, such as decreased cardiac performance usually found in myocarditis. Pericardial effusions are easily identified. MRI is also accurate but more expensive.

In patients with clinical evidence of acute myocarditis, echocardiography and radiographs of the chest show moderate or marked diffuse cardiac enlargement (Fig. 4.7). Ultrasonography or fluoroscopy will show decreased cardiac pulsations, especially at the left apex. A radiographic "cardiac series" will demonstrate enlargement of all chambers; the normal outline of the cardiac silhouette and the interventricular groove are lost. The right ventricle abuts against the sternum on the lateral view and the left ventricle overlaps the spine. The left atrium displaces the esophagus posteriorly and the left main bronchus superiorly. Oblique views confirm the atrial and ventricular enlargement. The lung fields are usually clear without evidence of congestion or edema.

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Fig. 4.7 Acute Chagas' myocarditis in a 6-year-old Brazilian boy. Posteroanterior (PA) (A) and left anterior oblique (LAO) (B) views of the chest show marked generalized cardiac enlargement with dilatation of all chambers. The hilar areas are not prominent and the lungs show no evidence of vascular congestion. Fluoroscopically the cardiac pulsations were decreased. The child had dyspnea and abdominal pain for 4 months and pitting edema in the lower legs for 2 months. The jugular veins were distended and the heart sounds were weak with a systolic murmur in the mitral area. The liver was palpable 10 cm below the right costal margin. Chagas' serology was positive. (Courtesy of Dr. Clovis Simao, Sao Paulo).

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