Because the pulmonary vascular bed is distensible, small emboli, even if multiple, may be asymptomatic unless they are infected (septic emboli) and cause pulmonary infection. Large emboli may cause acute dyspnea, pleuritic chest pain, cough, and hemoptysis. Hypoxia is common, as are nonspecific ST-segment and T-wave changes on the electrocardiogram (ECG). The P2 heart sound may be increased, and an S4 sound may be present.
Although the chest x-ray is usually normal, atelectasis or cardiomegaly may be seen. The measurement of D-dimers can be used as a screening test, but it must be interpreted in light of the probability of a pulmonary embolism. If the D-dimer is normal and the probability for embolism is low, then no further workup may be necessary. However, if the D-dimer is elevated, or if it is normal but the probability of embolism is moderate or high, then the diagnostic test of choice is a CT angiogram of the chest. Ventilation-perfusion scans may revealing defects in perfusion without matching ventilation defects, but they are difficult to perform in young children. Doppler or compression ultrasonography can be useful in assessing patients for lower extremity DVTs. For definitive diagnosis of pulmonary embolism, the gold standard is still pulmonary angiography, though with the improvement in CT angiography, angiograms are now rarely necessary. Children with pulmonary embolism without an obvious cause should be evaluated for hypercoagulable states, the most common of which is factor V Leiden.
Once a pulmonary embolism is suspected, the patient should be anticoagulated, usually with low-molecular-weight heparin. All patients should receive supplemental O2, and it is important to treat the predisposing factors. Thrombolytic therapy and surgical resection of emboli are rarely indicated. Occasionally an inferior vena caval filter needs to be placed to prevent recurrent emboli.
Cystic fibrosis (CF) is an autosomal recessive disorder that is the most common life-limiting genetic disease in whites. In the United States, the incidence of CF is approximately 1 in 3200 whites, 1 in 15,000 African Americans, and 1 in 31,000 persons of Asian heritage. The gene for CF, located on the long arm of chromosome 7, encodes for a polypeptide, the cystic fibrosis transmembrane regulator (CFTR), a chloride channel located on the apical surface of epithelial cells. CFTR is important for the proper movement of salt and water across cell membranes and maintaining the appropriate composition of various secretions, especially in the airways, liver, and pancreas. The most common mutation is a deletion of three base pairs resulting in the absence of phenylalanine at the 508 position (ΔF508). More than 1500 mutations of the CFTR gene have been identified.
The secretory and absorptive characteristics of epithelial cells are affected by abnormal CFTR, resulting in the clinical manifestations of CF. The altered chloride ion conductance in the sweat gland results in excessively high sweat sodium and chloride levels. This is the basis of the sweat chloride test, which is still the standard diagnostic test for this disorder. It is positive (elevated sweat chloride > 60 mEq/L) in 99% of patients with CF. Abnormal airway secretions make the airway more prone to colonization with bacteria. Defects in CFTR may also reduce the function of airway defenses and promote bacterial adhesion to the airway epithelium. This all leads to chronic airway infections and eventually to bronchial damage (bronchiectasis).
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Neck Masses Hoarseness Hemoptysis Chest Pain Diarrhea Constipation Hepatomegaly Eosinophilia Polyuria Failure to Thrive Alkalemia Hyponatremia