Radiographic Appearance
Besides the specific findings of lobar collapse listed
below, the radiograph will also show evidence of volume loss.
Examples include shift of the trachea, mediastinum and heart to the
side of the collapse, and elevation of the ipsilateral hemidiaphragm.
Since the right and left lower lobes are anatomically similar, the
appearance of lower lobe collapse is also similar. The lower lobe
collapses medially and posteriorly. On the PA radiograph, there will
be a dense, airless triangle of increased opacity at the medial
base. The triangle will extend from the hilum to the mid-portion of
the hemidiaphragm. The major fissure separates the airless lower
lobe from the rest of the aerated lung and causes the sharply
demarcated lateral border of the triangle. On the lateral view,
there will be increased opacity in the posterior base of the chest.
Notice that the normally visible hemidiaphragm becomes
indistinguishable posteriorly. This is due to the airless lower
lobe, which has collapsed posteriorly.
The PA radiograph will show only subtle findings in right middle
lobe (RML) collapse. The RML collapses medially against the heart.
The right heart border, which is normally sharply demarcated by the
air-containing RML becomes ill-defined as the RML becomes airless.
Evidence of volume loss is often absent, since the volume that the
RML occupies is small. On the lateral view, there will be a
triangular or band-like opacity extending from the hilum to the
anterior costophrenic angle. This represent the collapsed RM lobe.
on the lateral view.
The right upper lobe (RUL) collapses medially and superiorly. The
PA radiograph will show dense increased opacity at the right apex,
with a sharply defined inferior border. This border is caused by the
minor fissure separating normally aerated RML for the collapsed,
airless RUL. On the lateral view, you may see a triangular opacity
extending superiorly, with its apex at the hilum.
The left upper lobe (LUL) also includes the lingula, the left
anatomic equivalent of the right middle lobe. Therefore, collapse of
the RUL and RML together will be similar in appearance to LUL
collapse. The LUL collapses anteriorly and medially. On the PA
radiograph, there is hazy increased density in the left apex which
gradually clears inferiorly. There is no sharp inferior border, as
there is in RUL collapse, because there is no minor fissure on the
left. On the lateral view, there is a band of increased density
paralleling the anterior chest wall.
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Pathology
Types:
obstructive atelectasis (resorptive) airless lung
tumor, foreign body , mucous plug , stricture
passive atelectasis (compressive or elastic recoil)
low inspiratory volumes , pleural effusion , pneumothorax , pleural
masses
adhesive (decreased surfactant)
hyaline membrane disease
pulmonary embolus with infarction
cicatrization (fibrosis: local or general leading to volume loss)
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Treatment:
Atelectasis in the newborn is treated by suctioning the trachea to
establish an open airway, positive-pressure breathing, and
administration of oxygen. High concentrations of oxygen given over a
prolonged period tend to promote atelectasis and may lead to the
development of retrolental fibroplasia in premature infants.
Acute atelectasis is treated by removing the cause whenever
possible. To accomplish this, coughing, suctioning, and "bronchoscopy"
may be employed. In atelectasis due to airway obstruction with
secretions, chest physiotherapy is often useful. Chronic atelectasis
usually requires surgical removal of the affected segment or lobe of
lung. Antibiotics are given to combat the infection that almost
always accompanies secondary atelectasis. |
