1887

The pleural space

image of The pleural space
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Abstract

The pleural membrane consists of a single layer of flattened mesothelial cells that overlie a connective tissue layer containing blood vessels and lymphatics. There are two types of pleura: and . The parietal pleura line the inner surface of the wall of the thorax and the diaphragm, enveloping the central thoracic structures including the heart, great vessels and oesophagus to form the mediastinum. The chapter is divded into the following sections: Radiographic anatomy; Interpretive principles and Diseases.

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Figures

Image of 13.1
13.1 Dorsal plane view of the pleural layers. Note the continuity of the costal, mediastinal and diaphragmatic parts of the parietal pleura (outermost grey line). Inset: Transverse plane view. Note that the pleural space (between the grey lines) is not continuous with the mediastinum. H = Heart; L = Lungs; T = Trachea. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and are printed with her permission.
Image of 13.2
13.2 Close-up of a lateral radiograph of the caudodorsal part of the thorax of a 2-year-old Labrador Retriever bitch with pneumothorax, showing retraction of the lung margins from the thoracic wall and diaphragm (arrowheads). The lung tissue is increased in opacity but vascular markings can still be seen. Note the lack of lung markings in the area occupied by the gas (A).
Image of 13.3
13.3 Altered cardiac position in lateral radiographs with pneumothorax. This phenomenon can be explained by loss of the air-filled lung supporting the heart in its normal anatomical position within the thorax. Where pneumothorax is present on the dependent side, the lack of supportive lung tissue allows the heart to move towards the dependent thoracic wall. The space thus created between the cardiac apex and the sternum is highlighted by the X-ray beam causing the heart to appear elevated from the sternum by distance X. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and are printed with her permission.
Image of 13.4
13.4 Close-up of a lateral view of the thorax of a 1-year-old male Whippet with traumatic pneumothorax showing apparent elevation of the cardiac shadow from the sternum. The space between the apex of the heart and the sternum is occupied by free pleural gas (A). Note the absence of lung markings in this area. Patchy opacification (B) of the lung overlying the cardiac shadow is likely to represent contusion. VD thoracic radiograph of a 4-year-old Chihuahua with recent onset of right-sided chylous effusion. Notice the reduced size but normal shape of the right lung with sharp lung margins. VD radiograph of a 3-year-old Afghan Hound with chronic bilateral chylothorax, which was drained prior to radiography. Notice the interlobar fissure lines and rounded lung margins, indicating chronicity and scarring of the visceral pleura. The irregular margins of the cardiac silhouette are related to a previous pericardectomy. Corresponding postmortem photograph of the opened thorax of the same dog in (c), viewed ventrally. The lungs and heart are collapsed in the centre of the image and are covered in multiple layers of fibrous adhesions. There are marked fibrinous changes on the parietal pleura consistent with fibrinous pleuritis.
Image of 13.5
13.5 Location of the interlobar fissures. Since only fluid-filled fissures that are tangential to the X-ray beam are visible, the volume of fluid and the position of the patient will determine the fissures that are seen. Fissures of the lateral aspect of the left lung (looking medial to lateral) are more likely to be seen when the patient is in left recumbency. Fissures of the lateral aspect of the right lung (looking medial to lateral) are more likely to be seen when the patient is in right recumbency. Fissures on the dorsal aspect of the lungs are more likely to be seen when the patient is in dorsal recumbency. Fissures on the ventral aspect of the lungs are more likely to be seen when the patient is in ventral recumbency. DV thoracic radiograph from a dog with a moderate amount of pleural effusion. A thin radiopaque pleural line is indicated by the arrows. A = Accessory lobe; CdCr = Caudal part of the left cranial lobe; Cr = Right cranial lobe; CrCr = Cranial part of the left cranial lobe; Cs = Costodiaphragmatic recess; F = Interlobar fissure; LCd = Left caudal lobe; M = Mediastinal reflection; Md = Right middle lobe; RCd = Right caudal lobe; V = Caudoventral mediastinal reflection between the left caudal lobe and the accessory lobe (pleural fluid may accumulate adjacent to this reflection). Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and are printed with her permission.
Image of 13.6
13.6 DV thoracic radiograph of a mixed breed dog with a moderate pleural effusion. A wedge-shaped interlobar fissure is shown by the arrows.
Image of 13.7
13.7 Fluid distribution in lateral recumbency (shaded area). Fluid in the non-dependent hemithorax is suspended by the cranial mediastinum, producing a soft tissue opacity dorsal to the sternum and causing retraction of the ventral lung margins. The ventral cardiac margin and apex, and the dome of the diaphragm are obscured. Fluid in the lower costodiaphragmatic recess between the lung and the thoracic wall is not visible (perpendicular to beam) but contributes to an increased opacity throughout the thorax. Interlobar fissures are visible. The lungs retract in the direction of the arrows. Lateral thoracic radiograph of a dog with a large amount of pleural effusion. Notice the obliteration of the cardiac silhouette, scalloping of the ventral lung margins and interlobar fissure lines. (Reproduced from with permission)
Image of 13.8
13.8 Fluid distribution in dorsal recumbency (shaded area). Fluid collects dorsally, obscuring the descending aorta, and in the costodiaphragmatic angles, causing blunting of the lung margins. The diaphragmatic crura may be obscured but the dome remains visible. Lungs float upwards and pivot medially at the hilus to lie adjacent to the heart; therefore, the cardiac shadow remains visible. Fluid accumulates between the lungs and the lateral thoracic wall, and in the mediastinal reflection between the left caudal and accessory lobes. The cranial mediastinum remains visible as the cranial thorax is at a higher level than the caudal thorax. Fluid pools dorsally over a larger area than when the animal is in ventral recumbency, so fluid depth and consequent overall opacity are less than on the DV view. The lungs retract in the direction of the arrows. VD thoracic radiograph of a 9-year-old Dobermann with dilated cardiomyopathy and a small amount of cardiogenic pleural effusion. The enlarged cardiac silhouette is clearly visible and a small fissure line can be seen in the right cranial thorax, enabling a diagnosis of cardiac disease and cardiogenic effusion in this patient. The majority of the fluid is pooling in the lumbodiaphragmatic recess where it does not influence visibility of other thoracic organs. Fluid distribution in ventral recumbency (shaded area). Fluid pools ventrally. The lungs float upwards and pivot laterally about the hilus resulting in medial fluid accumulation, causing the mediastinum to appear widened and the cardiac shadow and diaphragm to be obscured. Little fluid accumulates laterally between the lung margins and thoracic walls. The thoracic cavity is narrower ventrally than dorsally, so when the animal is in sternal recumbency, fluid rises to a higher level making overall opacity greater than in a VD view. Interlobar fissures are visible. The lungs retract in the direction of the arrows. DV thoracic radiograph. The cardiac silhouette is completely obliterated by the surrounding pleural fluid, multiple pleural fissure lines are visible and diagnosis of heart disease is not possible. Even mild pleural effusion can completely obliterate the cardiac silhouette in the DV view. If tolerated by the patient, a VD view is advantageous in the presence of pleural effusion. (Reproduced from with permission)
Image of 13.9
13.9 Lateral radiograph of a 7-year-old Domestic Shorthair cat with a small volume of pleural effusion. An effusion of soft tissue opacity surrounds and effaces the ventral aspect of the cardiac silhouette. Falciform fat is seen ventrally within the abdomen.
Image of 13.11
13.11 VD thoracic radiograph of a cat with a left-sided unilateral pleural effusion due to pyothorax. The ipsilateral lung is completely collapsed and there is compensatory hyperinflation of the contralateral lung.
Image of 13.12
13.12 Normal radiographic appearance of the lumbodiaphragmatic recess of the cat. The psoas minor muscles have a more cranial origin in this species and are responsible for the soft tissue opacity in this region. Normal radiographic appearance of the lumbodiaphragmatic recess of the dog. Note that the lung fields extend up to and even slightly dorsal to the spine, in contrast to the cat. A cat with a moderate volume of pleural effusion. The caudodorsal tips of the lung lobes are retracted and rounded. Compare this with the normal appearance in (a).
Image of 13.13
13.13 VD thoracic radiograph of an 8-year-old Siamese cat with a bronchial carcinoma causing lobar resorption atelectasis. There is right caudal lung lobe collapse indicated by ipsilateral cardiac shift and border obliteration between the heart, lung, diaphragm and potential pleural effusion. VD radiograph with the cat in the same position but the table and X-ray tube tilted 25 degrees towards the cat’s head, allowing free fluid to move cranially within the thorax. The soft tissue opacity in the caudal thorax is reduced and there is an overall increased opacity in the cranial thorax. This relatively simple and well tolerated manoeuvre helped to diagnose the presence of pleural effusion.
Image of 13.15
13.15 VD thoracic radiograph of a 3-year-old mixed breed dog showing a skin fold (double white arrowheads), mimicking pneumothorax. Pulmonary vascular markings were visible lateral to the skin fold when viewed with a bright light. DV thoracic radiograph of a 7-month-old male Boxer with traumatic pneumothorax. The single white arrowheads outline the curved edge of a collapsed lung lobe, which is surrounded by free pleural gas (A). The black arrowheads show two rib fractures.
Image of 13.16
13.16 Lateral thoracic radiograph of a dog with a moderate volume of pleural effusion. Note that the lung margins remain sharp, consistent with an acute non-reactive effusion.
Image of 13.17
13.17 Lateral thoracic radiograph of a 13-year-old dog with a chronic chylothorax. Note the rounded edges of the retracted lung lobes in contrast to the sharp margins shown in Figure 13.16 . This dog also has several pulmonary osteomas seen as small irregular mineralized opacities.
Image of 13.18
13.18 Ultrasonographic image obtained via an intercostal window in an 8-year-old dog with a large-volume pleural effusion. The effusion was a transudate and is seen as completely anechoic. Echoic, collapsed normal lung can be identified surrounded by the effusion. Ultrasonographic image obtained in long axis across the cranial thorax of a 1-year-old cat. Rib shadows (R) are seen in the foreground and the cranial vena cava (CrVC) is seen as two echoic stripes with an anechoic lumen, running from left to right across the image. An echogenic effusion is present in both the left and right pleural spaces, surrounding the CrVC. This was in association with FIP.
Image of 13.19
13.19 Thoracic ultrasonographic image of a 3-year-old Siamese cat with a marked volume of slightly echoic pleural effusion. The image has been obtained with a linear transducer placed in a dorsal plane across several ribs at the level of the costochondral junctions. The ventrocranial mediastinum is seen as a narrow hyperechoic horizontal band surrounded by the pleural effusion in the left and right pleural spaces. The ribs (R) are seen in the foreground.
Image of 13.20
13.20 DV thoracic radiograph of a cat with pyothorax and abscess formation. An area of encapsulated fluid (F) is present in the right caudal thorax.
Image of 13.21
13.21 Ultrasonographic image showing multiple irregular pleural masses (M) in a 2-year-old Labrador Retriever with a large volume of haemorrhagic pleural effusion. The massesa are cauliflower-like and surrounded by the effusion. The final diagnosis was a rare neoplasm, telangiectatic osteosarcoma.
Image of 13.23
13.23 Lateral thoracic radiograph of an 8-year-old Rottweiler with a traumatic closed pneumothorax after being hit by a car. A moderate-volume pneumothorax is present. Gas lucency with no lung markings is present ventral to the cardiac silhouette and surrounds the caudodorsal lung lobe tips.
Image of 13.24
13.24 Lateral thoracic view of a 6-year-old Standard Poodle with tension pneumothorax. The cardiac shadow is markedly elevated from the sternum and the normal lung markings are absent. Note the extreme distension of the thorax with maximal opening of the lumbodiaphragmatic recess and the relative overexposure of the thoracic structures due to the replacement of lung tissue with free pleural gas. The margins of the severely collapsed lung lobes cannot be clearly outlined.
Image of 13.25
13.25 DV thoracic radiograph of a 9-year-old German Shorthaired Pointer that was involved in a road traffic accident. The cardiac silhouette is completely obscured, indicating pleural effusion, yet the overall opacity is decreased rather than increased, particularly peripherally. Close-up of (a) showing the left hemithorax viewed with an intense light source, reveals a lung margin separated from the rib cage by a gradient of peripheral free lucent gas and central free opaque fluid, consistent with a liquidopneumothorax. Lateral thoracic radiograph of a 2-year-old Domestic Shorthair cat with liquidopneumothorax. The cardiac shadow is partly obscured by free pleural fluid (B) and appears elevated from the sternum. Between the cardiac apex and the sternum is a pocket of pleural gas (A). Pleural gas also surrounds the caudodorsal margin of the collapsed lung. The margin of the lung (arrowheads) is more sharply defined than expected because the pleura are thickened. Note the normal triangular psoas minor muscle (C), with soft tissue opacity; seen in the cat between the lumbodiaphragmatic recess and the spine.
Image of 13.26
13.26 Lateral decubitus VD radiograph of the non-dependent hemithorax of a 2-year-old mixed breed dog with pneumothorax, showing the lung lobe margins retracted from the thoracic wall (arrowheads) and free pleural gas (A).

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