Thoracic Imaging 2003 - Society of Thoracic Radiology

WEDNESDAY
238
pathological process, such as viral infections, cytotoxic
chemotherapeutic agents, radiation injury and inhaled toxins.
The prognosis is poor, with progression of symptoms and death
often over a few years. The most common findings include
smooth interlobular septal thickening, patchy and/or centrilobular
ground glass opacities, and pleural effusions with normal
caliber pulmonary veins and left heart structures. (5,6) This latter
finding helps distinguish it from the more common cardiac
causes. These imaging findings have been reported to predict a
poor response to Prostacyclin therapy. (7)
Pulmonary capillary hemangiomatosis is a rare cause of PH,
representing the proliferation of thin walled capillary-like vessels,
which invade the veins and arterioles. It is associated with
intimal fibrosis, hemorrhage and venous stenosis. The etiology
is unknown, but may represent a form of low-grade malignancy
or metastatic dissemination of an angiosarcoma. Its imaging,
clinical course and prognosis are similar to pulmonary venoocclusive
disease. (6, 7)
Pulmonary Arterial Tumor Embolism
Pulmonary arterial tumor embolism often presents with progressive
dyspnea due to PH. It is a difficult diagnosis to make
clinically, requiring a high clinical suspicion. Intravascular
embolic disease on CT is usually manifested with numerous
branching “tree-in-bud” opacities; however, often have a beaded
appearance. Peripheral areas of infarction have been described.
(5) Of importance, despite its tree-in-bud manifestation, it is
unlikely to demonstrate any air trapping on expiratory maneuvers,
thus raising the suspicion for the diagnosis.
Hepatopulmonary syndrome/Cirrhosis associated PH
Hepatopulmonary syndrome is defined by the presence of
liver cirrhosis, intrapulmonary vascular dilation and hypoxemia.
Clinically patients often have platypnea and orthodeoxia. Two
major manifestations exist; type 1 (85%) has a spidery appearance
of the pulmonary vessels and type 2 (15%) associated with
numerous small arteriovenous fistulas. The former responds well
to 100% oxygen therapy while the latter does not. These vascular
changes are most notable in the lower lobes bilaterally. The
increased ratio of arterial diameter with the adjacent bronchus is
useful in making the diagnosis in patents with severe hepatic disease.
The exact etiology for some patients developing PH is
unclear, but may relate to the increased pulmonary flow and
vasoactive or vasotoxic substances normally degraded by the
liver, which reach the pulmonary circulation. (5,6)
Sickle Cell Anemia
Sickle cell anemia is associated with multiple pulmonary
abnormalities, including PH, though the latter is reported as a
rare complication. The precise etiology may relate to the multiple
episodes of acute chest syndrome classically described in
this patient population. (8) Consolidation and or ground glass
opacities are most commonly seen, representing either hemorrhage/infarction
or pneumonia. Multiple sickling events with
occlusion of the microvasculature likely predisposes to eventual
PH. Concurrent pulmonary fibrosis may be present.
Pulmonary Vasculitis
Pulmonary vasculitis is a disease spectrum of inflammation
directed towards the small arteries and capillaries. There are
numerous causes of this pathological reaction, including
Wegener’s Granulomatosis, Churg-Strauss syndrome, collagenvascular
diseases and granulomatosis reactions to talc injection.
The greater proportion of vessels involved increases the likelihood
of developing PH. Patchy ground glass opacities and/or
centrilobular ill defined ground glass nodules are described
imaging findings, especially in active disease. (5) These correlate
with the widespread perivascular inflammation and hemorrhage.
REFERENCES:
1. Clinical Classification of Pulmonary Hypertension. 1998 World
Symposium on Primary Pulmonary Hypertension.
2. Cardiac Radiology: The Requisites. Miller S. Mosby 1998. pp
23-25.
3. Reading the Chest Radiograph: A Physiologic Approach. Milne
E., Pistolesi M. Mosby 1993. pp164-167.
4. Gosselin M, Rubin G. Altered intravascular contrast material
flow dynamics: Clues for refining thoracic CT diagnosis.
Pictorial Essay AJR 1997;169:1597-1603.
5. High-Resolution CT of the Lung. 3rd edition. Webb R, Muller N,
Naidich D. Lippincott, Williams & Wilkins, 2001.
6. Diagnosis of Diseases of the Chest. 4th edition. Fraser, Muller,
Colman, Pare. Chapter 50: Pulmonary Hypertension. W.B.
Saunders Company: pp 1879-1945.
7. Resten A., Maitre S., Humbert M., et al. Pulmonary Arterial
Hypertension: Thin Section CT Predictors of Epoprostenol
Therapy Failure. Radiology 2002;222:782-788.
8. Aquino S, Gamsu G, Fahy J, et al. Chronic pulmonary disorders
in sickle cell disease: findings at thin-section CT.
Radiology 1994;193:807-811.