The pleura consists of a visceral and parietal layer.
The visceral pleura covers the lungs and interlobar
fissures, whereas the parietal pleura lines the ribs,
diaphragm, and mediastinum.
A double fold of pleura extends from the hilum to the
diaphragm to form the inferior pulmonary ligament..
There is no communication between the two pleural
cavities.The pleural space is a potential space that
contains 2 to 10 mL of pleural fluid in the normal
The main manifestations of disease in the pleura
Pleural thickening (which may or may not be calcified).
Pleural air (i.e., pneumothorax).
Primary disease of the pleura is rare. Most pleural
abnormalities result from disease processes in other
Physiologic Mechanisms in the development of Pleural Effusions
Increase in hydrostatic pressure in microvascular
circulation (congestive heart failure)
Decrease in osmotic pressure in microvascular
circulation (Hypoalbuminemia, Cirrhosis).
Decrease in pleural pressure (Atelectasis).
Increase in permeability of microvascular circulation
(Inflammatory conditions, Neoplasms).
Impaired lymphatic drainage (Tumor, Fibrosis).
Transport of fluid from abdomen (Ascites).
1- Standard Radiography
Free pleural effusion demonstrates a
meniscus sign, which is a concave,
upward-sloping interface with the lung
that causes sharp or indistinct blunting of
the costophrenic angle.
Sub pulmonary effusion:
On the frontal view, this produces a characteristic
appearance with elevation of the apparent ipsilateral
hemidiaphragm, flattening of the medial aspect, and
displacement of the peak of the apparent diaphragm
On the left side, this is easy to recognize because of
separation of the stomach bubble from the apparent left
Subpulmonic effusion. On the left,
there is separation of the
apparent hemidiaphragm from
the stomach bubble.There is also
minimal blunting of the lateral
costophrenic angle. On the right,
a large effusion extends to the
major fissure, subtending a lucent
area that represents the superior
segment of the right lower lobe
A massive effusion
produces a complete
or nearly complete
opacification of a
displacement of the
mediastinum to the
Moderate to large amounts of
pleural effusion may be
missed on supine
layer posteriorly and produce
a generalized increase in
opacity of the hemithorax,
through which the pulmonary
vessels can be visualized
Fluid may occasionally
accumulate within fissures,
and these accumulations may
produce the appearance of a
mass or pseudotumor
Differentiation from a mass
can be easily made because
the fluid is free and shifts on
Pleural fluid collections may be anechoic or
echoic, and they may change shape during
respiration. Most collections are anechoic and
are delineated by an echogenic line of visceral
pleura and lung. Anechoic effusions are usually
transudates, whereas effusions that contain
septations represent exudates in approximately
80% of cases
3- Computed Tomography
Pleural fluid can be distinguished from
ascites by several CT features, including
the displaced crus sign, the interface
sign, the diaphragm sign, and the bare
Displaced crus sign.
The pleural fluid lies
inside the crus of the
and displaces it away
from the spine.
Interface sign. A hazy,
indistinct interface is
seen between the
pleural effusion and
(arrows), and ascites
can be seen
Diaphragm sign. Ascites
(A) lies inside the
diaphragm (arrows) and
produces a sharp
interface with the liver.
The pleural effusion (E)
is visualized outside the
4- Magnetic Resonance Imaging
The role of MRI in the evaluation of the pleura is
somewhat limited. MRI does provide certain
advantages because of its ability to image the
thorax directly in the axial, sagittal, and coronal
planes. MRI may be slightly superior to CT in
the characterization of pleural fluid (high T2 &
Pneumothorax in an
extremely thin visceral
pleural line can be seen
extending along the
lateral aspect of the lung
to the apex
Large bullae simulating
lung is lucent, devoid of
vessels, and almost
completely replaced by
bullae.The bullae have
Large tension pneumothorax.
The large pneumothorax on
the right is associated with
almost complete collapse of
the right lung.The margins of
the lobes can be seen.There
is evidence of tension, with
shift of the mediastinum to the
left and depression of the
The erect frontal view
shows an air-fluid level at
the base of the left
pleural space (black
pneumothorax can also
be seen extending along
the lateral chest wall and
at the apex
The most common focal pleural abnormalities
Localized pleural tumors.
And local extension of bronchogenic
Progression of pleural plaques. A, Axial CT shows bilateral pleural
plaques and calcification (arrows). B, Axial CT 5 years later shows
progression of pleural plaques (arrows) and development of new
plaques (open arrows).
pleural plaques can
adjacent to the lateral
chest wall (arrows).
The apices and
Localized Pleural Tumors
Localized pleural tumors are relatively
uncommon.They usually are one of two
types: fibrous tumors of the pleura or
Liposarcomas are rare, but the pleura
commonly may be invaded locally by
adjacent bronchogenic carcinoma.
Fibrous tumor of the pleura. A, The precontrast CT scan shows a mass posteriorly of
fairly uniform attenuation that makes an acute angle with the lateral chest wall. B,
After the administration of contrast, focal areas of enhancement can be appreciated
Fibrous tumor of the pleura. A, Spin-echo, T1-weighted MRI shows a mass
posteriorly with signal intensity equal to that of muscle. B, On the T2-weighted
image, most of the mass has low signal intensity with a slightly bright rim.
Lipoma. CT shows an
intra pleural tumor of
( 90 HU).−
Benign and malignant diseases may
cause diffuse pleural abnormalities.
2- Malignant tumors such as malignant
mesothelioma and metastatic carcinoma.
The radiographic definition of diffuse pleural
thickening is somewhat arbitrary, and there is no
general consensus on a definition.
However, it has been suggested that diffuse pleural
thickening consists of a smooth, uninterrupted pleural
opacity extending over at least one fourth of the chest
wall, with or without obliteration of the costophrenic
The CT definition that has been used in describing
asbestos-related changes consists of thickening that
extends more than 8 cm in the cranio-caudal direction
and 5 cm laterally and a pleural thickness more than 3
Calcified fibrothorax in a patient with pneumothorax treated many years ago for
tuberculosis. There is extensive calcification surrounding the entire lung. A, On the
frontal view the calcification can be easily localized to the visceral pleura (arrow). B,
On the lateral view, markedly thickened pleura can be seen anteriorly (arrows).
CT shows bilateral,
diffuse thickening but
Benign, diffuse pleural
thickening caused by
CT shows smooth
nodularity involving the
lateral and posterior
pleural surfaces but not
the mediastinal pleural
Malignant mesothelioma. A, The diffuse pleural thickening on the right is nodular
and extends along the mediastinal pleural surface (arrow). The volume of the right
hemithorax is slightly reduced. B, Coronal reformation image shows the extent of
pleural disease to greater detail and shows intrafissural extension (arrow).
Malignant mesothelioma. A and B, There is diffuse, circumferential pleural
thickening on the right, which is lobular. The tumor extends into the chest wall
(arrows). Notice the pleural plaques on the left.
Malignant mesothelioma. A, Standard
radiograph shows diffuse pleural thickening
on the right and contracture of the right
lung. B, CT shows involvement of the
peritoneum and liver.
Malignant mesothelioma. MRI shows
extensive left mesothelioma involving the
pericardium (A) (arrows) and diaphragm
Metastatic disease to
the right pleural
space from renal cell
carcinoma. Notice the
Invasive thymoma. A, Imaging shows a large, anterior mediastinal mass (arrows).
B, Nodular pleural thickening is present along the left mediastinal pleural surfaces
(arrows). Notice the left pleural effusion.