Systemic and Lung Diseases
In this chapter, examples are used to illustrate how certain systemic and lung diseases, not already covered in previous chapters, can manifest and affect the appearance of the pulmonary vasculature. The diseases explored here include sarcoidosis, hepatopulmonary syndrome, sickle cell disease, bronchopulmonary dysplasia, idiopathic pulmonary hemosiderosis, emphysema, pulmonary Langerhans cell histiocytosis, usual interstitial pneumonitis, lymphangiomatosis and the angiomatous diseases, which include capillary hemangiomatosis and pulmonary capillary veno-occlusive disease.
Sarcoidosis is a systemic noncaseating granulomatous disease of unknown etiology that affects the mediastinum, lungs, and other organs to varying degrees.
Pulmonary hypertension occurs in patients with end-stage lung disease due to sarcoidosis; several mechanisms may contribute, including fibrotic destruction of the capillary bed and resultant chronic hypoxemia, extrinsic compression of the major pulmonary arteries by enlarged lymph nodes, and secondary pulmonary veno-occlusive disease.
Hepatopulmonary syndrome is defined as the triad of hepatic dysfunction, intrapulmonary vascular dilatation, and hypoxemia.
Clinically, it manifests as progressive dyspnea in patients with cirrhosis.
It occurs in 50% of patients with chronic liver disease of any cause.
It is not to be confused with portopulmonary hypertension, which is pulmonary hypertension due to increased vascular resistance in patients with portal hypertension.
Normal pulmonary capillaries are between 8 and 15 [H9262]m in diameter; in hepatopulmonary syndrome, they are 15 to 100 [H9262]m in diameter.
The hypoxemia is due to the presence of numerous tiny intrapulmonary shunts.
Radiographic findings include bilateral basilar nodular or reticular opacities on chest radiograph, heterogeneous uptake on perfusion lung scan, and peripheral arteriolar dilatation on computed tomography (CT) or magnetic resonance imaging (MRI; Fig. 11.3).
Sickle cell disease is a systemic disease that can result in occlusion of the small pulmonary vessels.
In the acute chest syndrome, capillary obstruction by sickle cells is accompanied by in situ thrombosis.
Imaging can demonstrate ground-glass opacification or extensive consolidation due to hemorrhagic edema, which is caused by ischemia, infarction, or infection and is responsible for precipitation of the acute chest syndrome (Fig. 11.4).
CT can show mosaic attenuation, thought to be related to secondary pulmonary lobules with hypoperfusion adjacent to normal or hyperperfused lobules (Fig. 11.4).
Chronic changes are seen in individuals experiencing repeated acute episodes, with parenchymal bands due to fibrosis of infarctions (Fig. 11.4).
Eventually, in patients with persistent occlusion of the microvascular bed, cor pulmonale develops, manifested as dilatation of the pulmonary arteries and right ventricular hypertrophy.
In premature neonates, the high pressures of oxygen delivery can result in necrotizing vasculitis, bronchiolitis, and alveolar septal injury.
CT features in older survivors include extensive areas of decreased lung attenuation, within which the size and number of vessels and bronchi are reduced as a consequence of chronic changes in the lung parenchyma, vessels, and airways (Fig. 11.5).
Idiopathic pulmonary hemosiderosis is a rare cause of diffuse alveolar hemorrhage and, by definition, of unknown etiology.