Pleural effusion can occur in isolation or associated with other lung disorders, mediastinal or chest wall. Often the cause is apparent on chest radiograph, for example, when accompanied by signs of heart failure or pneumonia. Imaging studies play a key role in the diagnosis and quantification of the spill.
The ultrasonography and computed tomography can also specify the distribution and some special features of the spill and to guide invasive procedures such as pleural biopsy and drainage, but are not able to distinguish the characteristics of the liquid to differentiate between transudate and exudate.
Chest X-ray
The examination of a patient’s choice against raising the suspicion of a pleural effusion. The radiographic signs depend on the distribution of the liquid and, therefore, whether it is free or loculated and the patient’s position. In standing position, to about 75 ml of liquid can be treated exclusively in the subpulmonary space between the bottom surface of the lung and the diaphragm. Radiographically, this manifests as an apparent elevation of the diaphragm, with flattening of the medial aspect. The left side shows a marked separation between the gastric bubble and the lung base. A distance between these structures equal to or greater than 2 cm is highly suggestive of subpulmonary effusion, a finding that is most evident in the lateral view. To demonstrate a subpulmonary pleural effusion or against doubtful findings, can perform a chest radiograph in lateral recumbency on the affected side, which is more sensitive than that obtained in standing position, being able to detect as little as 10 ml.
As the fluid continues to accumulate, exceeds the subpulmonary space: a spill of approximately 100 ml of liquid obliterated costophrenic recess back, which is the most dependent on the chest, while with 200 ml clears the lateral recess, which be seen radiographically as a loss of the acute angle formed by these structures, both front projection and in lateral as well as lung separation of the ribs.
The fluid surrounding the lung, which floats, retaining its shape in all stages of collapse. The spill gives rise to an increase in density in the affected hemithorax, which does not erase the pulmonary vasculature and the upper edge appears oblique and concave, with its top toward the lateral chest wall, although the upper limit of physically Liquid is truly horizontal. This is because in the lateral rays only pass through liquid, while toward the center is interposed aerated lung, which decreases the opacity film.
In a massive spill, the commitment appears completely opaque hemithorax. To differentiate this finding from a lung full, look for signs of occupation of space and mass effect exerted by the spill. These are the deviation of the trachea and mediastinal structures toward the opposite side and caudal displacement, flattening or inversion of the diaphragm, convex lower surface.
In the patient in supine position (usually obtained in X-rays in the most seriously ill) fluid accumulates more cephalad to the area of the back, which is the area dependent on this position. The radiograph shows a slight increase in the density of the affected hemithorax costophrenic sinus obliteration and an opaque band around the pulmonary apex (“cap” apical).
Occasionally, loculated pleural fluid accumulates as “atypical” in the interlobar fissures, along the posterior mediastinum or situation. This can simulate a mass intatorácica and is due to local lung disorders, especially atelectasis.
Loculated pleural effusion appears as a liquid that occupies dependent portions of the pleural space-like mass, homogeneous and does not vary to reposition the patient. It is seen in empyema, hemothorax, chylothorax, and tuberculosis pleuritis.
Ultrasonography pleural
The pleural ultrasonography is indicated when there are findings inconclusive to the chest radiograph and is the method of choice to guide the diagnostic or therapeutic pleural puncture. Most spills appear as hypoechoic collections anecogénicas or delineated by an echogenic band that represents the visceral pleura and lung.
Unlike radiography, pleural ultrasonography can sometimes suggest the type of stroke. Most are transudates or an hypoechogenic, but as can be exudates, this sign has no diagnostic value, however, a spill with septum, heterogeneous aspect or echoes evenly distributed, it is usually an exudate. Other findings, such as the simultaneous condensation of a pulmonary nodule or lung or pleural mass or pleural thickening are also suggestive of exudate.
The combination of chest radiography and ultrasonography for the diagnosis of pleural effusion has greater diagnostic accuracy (98%) to be used separately (68% and 92% respectively),
Computed Tomography
CT is particularly useful in the assessment and management of loculated pleural collections. They can be differentiated from lung masses by their location, configuration, lenticular, smooth edges and because it shifts the underlying lung parenchyma. It is also the best method for distinguishing a lung abscess, pleural empyema peripheral, use of intravenous contrast may reveal thickening of the pleura heavily irrigated, suggestive of an empyema. The presence of blood in the pleural space is seen as a hyperdense material that can form a liquid level. It is also useful to choose the best entry route and site location for a drainage pipe.
Pleural Metastasis
Pleural tumors are more common and the second leading cause of pleural effusion in patients older than 50 years. The tumors most frequently involve the pleura are lung cancer (36%), breast (25%), lymphoma (10%), ovarian (5%) and gastric (5%). In 10% of cases the primary is unknown. The main mechanism that causes stroke is blockage of the stomata of pleural lymphatic vessels.
Radiologically present as pleural effusion important, being the most common cause of massive stroke in adults. You can also appreciate pleural nodules or masses and extensive pleural thickening, which is best evaluated with CT. If the disease is unilateral, it is radiologically indistinguishable from malignant mesothelioma.
Primary Pleural Tumors
Fibroid tumors of the pleura
They are localized tumors that originate in the sub-mesothelial layer of the pleura and not related to asbestos exposure. These tumors may arise from the visceral pleura or the parietal pleura. In 40% of cases are malignant and 20% invade the chest wall or lung parenchyma neighbor. Surgery is curative in all benign tumors and about half of evildoers.
Half of cases are asymptomatic and examinations at a chest radiograph requested otherwise. Be seen radiographically as masses of smooth convex contour and net, with uniform density. Their margins obtuse angles with the chest wall or mediastinum and displacing the lung parenchyma. Pedunculated masses tend to be benign, while more than 10 cm are usually malignant. In 10% of cases are associated with pleural effusion.
CT may show areas of necrosis, hemorrhage or calcification and with intravenous contrast can be seen varying degrees of vascularity. There are signs that can distinguish between benign or malignant.
Malignant Mesothelioma
As fibrous tumors of the pleura, this neoplasm is rare, representing less than 5% of pleural tumors. Over 80% of cases there is a history of asbestos exposure as exposed workers are 300 times greater risk of developing the tumor than the general population. It is estimated that 6% of asbestos workers will die from this disease.
The chest radiograph and CT appears as a diffuse pleural thickening, irregular or nodular, most often associated with pleural effusion important that sometimes occupies more than 50% of the hemithorax. Characteristically, the affected hemithorax have decreased lung volume secondary to incarceration by the tumor, which forms a true shell. Occasionally, this tumor presents as a localized pleural mass or nodules. In one third of cases occur in the pleural plaques contralateral hemithorax.
CT is the examination of choice for malignant mesothelioma etapificar as it can demonstrate pericardial effusion, invasion of the mediastinum or the chest wall and intrathoracic lymphadenopathy.
Pleural plaques
Represent collections of hyalinized collagen in the layer of the parietal pleura submesothelial. They are the most common manifestation of asbestos exposure and its prevalence is correlated with the intensity of exposure and the time interval from the initial contact. 10% of workers exposed to asbestos pleural plaques present after 20 years and over 50% after 40 years. Between 4 and 8% of the general population showed pleural plaques on chest radiograph.
These lesions mainly involve the lateral and posterior aspects of the parietal pleura, rarely appear in the anterior and respect the lung apices and costophrenic angles. The thickness of the plates varies from 1 to over 10 mm, being thicker over the ribs. They are bilateral in 75% of cases and tend to be asymmetrical.
Chest radiography allows pesquisar pleural plaques, for which you must add oblique. They look like pleural thickening should be differentiated from focal subpleural fatty deposits, which tend to be bilateral and symmetrical and are located in the middle third of the lateral chest wall.
Computed tomography with high resolution technique is the most sensitive and specific location you view diaphragmatic plaques and distinguish subpleural fat.
Pleural calcification
Pleural plaques tend to calcify and about 40% of people exposed to asbestos exhibited radiologically apparent calcification. When viewed tangentially, producing a white, calcified, separated from the wall by a soft tissue density. Seen from the front appear as irregular linear densities located at the center of the thin plate representing opacity. The TAC is also in this case the most sensitive diagnostic method. The differential diagnosis includes pleural calcifications secondary to hemothorax, empyema or tuberculosis, which are usually unilateral, large and affect the visceral pleura.
Pneumothorax
Chest X-ray examination is required before the clinical suspicion of pneumothorax. The most important radiological sign is the visualization of the visceral pleura as a line that separates the lung radiodense of avascular gas collection. This sign is evident in the patient in standing position, since the air accumulates in apicolateral situation and can be viewed as little as 50 ml. Other findings include lung collapse, which preserves its shape even in a significant pneumothorax, and expansion of the affected hemithorax due to the decrease of the elastic traction and reduced lung volume. To highlight gas in the pleural space and display small pneumothorax, one resorts to special screenings, such as the Front exhalation, decreasing lung volume, making it more opaque in contrast to the pneumothorax. It is also used in lateral projection on the healthy side horizontal beam that detects small amounts of gas, in this position accumulate under the chest wall that was up.
In the patient supine, radiological signs of pneumothorax are subtle and requires the presence of more air in the pleural space for a definitive diagnosis. The air accumulates in the anteromedial region, area or subpulmonary costophrenic recess. The interposition of air will produce an increase of radiolucency, which is especially evident in areas with soft shadows, as in the hypochondria, giving rise to the sign of “radiolucent hypochondriac.” You may also be abnormally deep costophrenic angle and transparent. The outline display mediastinal or cardiac silhouette in a very clear and asymmetric with respect to the other side should suspect the presence of pneumothorax. CT is very sensitive to demonstrate pneumothorax in patients in the prone or equivocal findings on radiography.
The exact quantification of a pneumothorax is not easy, so for clinical use indirect indicators are used to approximate: if the distance between the chest wall and the visceral pleura is greater than 3 cm and 4 cm at the apex, will be needed pleural drainage tube to re-expand the lung.