How to read a Chest X-Ray (Basics)

The proposed system for looking at a radiograph of the chest involves remembering part of
the alphabet:

A-airway
B-bone
C-cardiac
D-diaphragm
E&F-equal (lung) fields
G-gastric bubble
H-hilum (and mediastinum)

AIRWAY
ŠLook at the trachea and its branches: check the site, size, shape, and shadow (4 S’s).
ŠIs it patent, or narrowed indicating stenosis or edema? Is it central? (in children it should be
straight but in adults it can deviate to the right due the aortic arch)

BONE
ŠLook at and compare the bony structures paying attention to site, size, shape, shadows and borders:
(clavicles, ribs, scapulae, thoracic vertebrae, and humeri).
ŠAny fractures? Using a pointer follow along the smooth edges of each bone looking for an interruption of the smooth line.
ŠAny lytic lesions? Look for discrete darker areas or a change in bone density.
ŠAny bony deformity? (rachitic rosary at the costochondral joints seen in rickets)
ŠAny extra? (cervical ribs)
ŠAny missing bones? (absent vertebral arches in spina bifida occulta)
ŠLook for lateral deviations of the vertebrae in scoliosis.

CARDIAC
ŠTake note of the cardiac site, size, shape, shadows and borders.
Site: is it located on the right or left?
Size: is it less than half the transthoracic diameter? (i.e. is the largest diameter of the heart
less than half the largest diameter of the thorax)
Shape: is it ovoid with the apex pointing to the left?
Shadows: any change in density?
Borders: is it clear or well defined?
-unclear right border suggest middle lobe consolidation.
-unclear left border suggest lingular lobe consolidation.

DIAPHRAGM
ŠLook at the outline of the diaphragm; it should be clear and smooth.
ŠRight hemidiaphragm should be higher (2-3cm) than the left:
-highest point on the right should be in the middle of the right lung field.
-highest point on left should be slightly lateral to the middle of the left lung field (see Figure 1).
-deviation may indicate pneumothorax. ŠAre the costophrenic angles well defined?
-whiteness immediately above the diaphragm indicates pleural effusion or consolidation.
-the presence of fluid will produce a meniscus (Meniscus Sign) or a concave upper border
ŠIs there air below each hemidiaphragm indicating bowel perforation?
ŠIs the diaphragm below the anterior end of the 6th rib on the right? If so, this indicates hyperinflation.

EQUAL (lung) FIELDS
ŠDivide lung fields into zones: upper, middle, and lower zones
-upper: from the apex to 2nd costal cartilage
-middle: between 2nd and 4th costal cartilage
-lower: between 4th and 6th costal cartilage
ŠLook for equal radiolucency (or blackness due to air filling) between the left and the right lungs
zones.
ŠLook for any discrete or generalized grey/white shadows (described as opacity/patchy shadows)
ŠThe horizontal fissure on the right, divides the upper and middle lobes:
-from the hilum to the 6th rib at the axillary line
ŠLook for vascular markings:
-indicating pulmonary hypertension pruning

Š
More specifically look for:
-Air bronchograms are visible air-filled bronchi, outlined by surrounding consolidation.
-Bat’s wing distribution describes one of two patterns of consolidation (the other pattern being lobar);
refers to the bilateral opacification spreading from
the hilar regions into the lungs (sparing the peripheral lung areas) signifying extensive alveolar disease. The causes of bat’s wing are: pulmonary
edema in heart failure, fluid overload, hypoproteinemia, blood transfusion reaction, and others.
-Reversed bat’s wing distribution are alveolar opacification in the peripheral lung fields with sparing of
the central areas seen in fat embolism 1-2 days following a bone fracture.
-Kerley A, B, and C lines which are fine lines running through the lungs representing thickened connective tissue septae seen in intersitial pulmonary
edema.
ŒKerley A lines are found in the upper lobes.
ŒKerley B lines are short (1-2 cm) horizontal line in the lower lobes.
ŒKerley C lines are diffusively distributed through the entire lung.
These Kerley lines may be associated with cardiac enlargement and pleural effusions.

GASTRIC FUNDUS
ŠLook for an air bubble under the left hemidiaphragm.
ŠLook for diaphragmatic hernia on the right or left.

HILUM AND MEDIASTINUM
ŠLook at the hilum (which consists of main bronchus and pulmonary arteries)
-the left should be higher than the right.
ŠCompare the convex shapes and densities on both sides.
ŠThe paratracheal lines are thin lines of the right and left tracheal margins which are thickened in lymphadenopathy.

Source:
TSMJ Volume 2 2001: Clinical Medicine
www.tcd.ie/tsmj