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Chapter 37 • The Chest X-ray 451
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away from a tension pneumothorax. Thickening of the
trachea may indicate lymph node enlargement or an upper
mediastinal tumor.
Clavicles
The clavicles should be present and symmetrical and
located at the second and third intercostal spaces. Scrutinize for fracture lines, which appear black on the
image because of air space surrounded by white bone
and tissue.
Bony Thorax
Note the size and shape of the thorax. Scoliosis is visible
on the frontal image, whereas kyphosis and funnel chest
are best seen on the lateral view. Examine individual
shoulder girdles for shape, size, and contour. Bony
structures are evaluated for deformity, mineralization,
density, and cortical thickness, as well as for fractures.
Scapulae
The distance between the scapulae is increased when
the shoulders are rotated forward in the PA image. This
position also ensures that the scapulae will be out of
the lung elds. Observe for fractures and symmetry.
Thoracic Spine
Look through the mediastinum and lungs to view the
spine and observe for symmetry of the rib cage. Vertebral evaluation is best done on the lateral image. Look
for compression fractures, height of vertebral bodies,
disk spaces, and density of bones.
1
2
3
4
5
6
7
8
9
10
11
FIGURE 37-3 Respiratory lung movement. Full expiration with
the ribs numbered. The anterior ribs are labeled with a suffix.
(From Ballinger PW, Frank ED: Merrill’s atlas of radiographic
positions & radiologic procedures, ed 10, St Louis, 2003,
Mosby.)
2A
3A
4A
5A
6A
7A
8A
vertical markers. Interspaces are numbered using
the posterior rib and according to the rib above.
Observe the widths of the intracostal spaces, which
should be equal bilaterally.
Decreased lung volume narrows the intracostal spaces.
Conditions that cause this include interstitial brosis
(bilateral) or a foreign body (unilateral). Increased lung
volume increases the intracostal spaces in such conditions
as asthma and COPD.
Ribs and Intracostal Spaces
Count the posterior ribs; 10 should be visible. If eight
or fewer ribs are visible, this is either a poor image or
an expiratory image. Be careful to begin the rib count
at the rst thoracic vertebra. Locate the anterior end of
the rst rib just below the medial end of the clavicles,
follow it back to its posterior end, and start counting
ribs (Figure 37-3). The posterior ribs are more superior than the anterior ribs. Check ribs side to side and
completely to the lateral end. Most fractures occur on
the lateral parts of the ribs. Normal ribs appear sloped
at the edges; ribs that are horizontal or attened indicate emphysema or chronic obstructive pulmonary
disease (COPD).
Describe abnormalities using ribs or interspaces
as location markers horizontally and chest lines as
Diaphragm
The diaphragm separates the abdominal contents
from the pleural cavity. Any changes in these areas
can be seen radiographically to affect the diaphragm.
Count down the posterior ribs near the spine; the diaphragm should be at the tenth or eleventh rib. The
diaphragm should have a curve that is shaped upward.
The right side is usually higher (1 to 2 cm) than the
left because the liver is located under the right hemidiaphragm; this will be more visible on a lateral
image of the diaphragm. Note if the diaphragm is
elevated or attened.
Suspect hepatomegaly in patients who have
marked asymmetry of the right diaphragm. A unilateral elevation of the diaphragm is seen with a
pneumothorax.
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Patients who do not take a deep breath, who have
ascites or intestinal obstruction, or who are in the
third trimester of pregnancy will have elevated diaphragms. A diaphragm that is low and at indicates
structures within the thorax are enlarged, as seen
in COPD.
Note any free air in the peritoneum visible below
the right lower diaphragm edge. The air appears as
lucency (decreased opacity) under the crescent of the
hemidiaphragm, typically as result of a perforated
viscus.
Costophrenic Angle
The edge of the diaphragm curves downward at the
costophrenic junction, meeting the ribs and forming an
angle that is sometimes referred to as the letter “V” on
its side. This angle should be sharp. Blunting of the
angle is caused by pleural effusion, pneumonia, neoplasm, or brosis (Figure 37-4).
Gastric Air Bubble
The gastric air bubble should always be on the examiner’s right side as the image is viewed (the patient’s
left side). The stomach lies close beneath the left
diaphragm. The liver, spleen, and kidneys are occasionally visible and should be noted for size.
Air-filled
trachea
Apex
Mediastinum
The mediastinum is located between the sternum anteriorly, the vertebral bodies posteriorly, and the lungs laterally. It encompasses a number of structures including
the heart and its large vessels, as well as the trachea,
thymus, and lymph nodes.
A prominent structure is the aortic arch (see
Figure 37-4). The arch is the rst prominent bulge along
the left mediastinal border. Assess for size and length. As
patients age, the aorta increases in thickness and length.
An increase in size is also seen in an aortic aneurysm.
The ascending aorta is the small bulge on the right.
Hilar Area
The hilar area contains the roots of the lungs and is
where the major bronchi and pulmonary vessels project outward.
Note the size of the hilar area. Increased fullness
or size generally indicates lymphoma, metastatic carcinoma, tuberculosis, or fungal (Histoplasma) adenopathy.
Pulmonary Vasculature
Pulmonary arteries become smaller as they progress out
to the chest periphery, ending approximately 1.5 cm
from the pleural surface. Normal markings extend approximately one third of the way into the lung elds.
Increased pulmonary pressure causes engorgement
of the pulmonary vessels, and increased markings are
seen that resemble a branching tree. When engorgement occurs, a buttery appearance is seen. Pulmonary
edema causes blurred borders and hilar clouding.
Aortic
arch
Lung
Heart
Diaphragm
Costophrenic
angle
FIGURE 37-4 Normal costophrenic angle. (From Ballinger
PW, Frank ED: Merrill’s atlas of radiographic positions
and radiologic procedures, ed 10, Vol 1, St Louis, 2003,
Mosby.)
Heart
Measure the size of the heart using a ruler. The heart
should be less than 50% of the transverse diameter of
the thorax. The measurement should be compared to the
widest thoracic diameter (found below the diaphragm
and between the ribs), resulting in the cardiac/thoracic
(C-T) ratio. The normal ratio is 1:2 (Figure 37-5).
Left ventricular hypertrophy extends the heart border
to the left, increasing the size of the heart and decreasing
the C-T ratio.
Look for the silhouette sign, which occurs when
two structures have the same density and are in contact
with each other, resulting in a loss of borders on the
x-ray. Because the right and left borders of the heart
are air-lled, lesions in the lung cause the differentiation of the heart border to be lost.
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How do I assess the lateral view?
Key Questions (to self)
n In what position is the patient?
n How do I know the image quality is good?
n Am I using a systematic approach to reviewing the
image?
FIGURE 37-5 The normal cardiac-thoracic ratio is 1:2.
Pleura
Follow the pleura around the lungs and note any thickening, calcication, effusion, or pneumothorax.
Pleural thickening is seen as increased soft tissue
around the periphery of the lung. An effusion will
blunt the costophrenic angle. A pneumothorax will
pull the visceral pleura into the lung eld, away from
the chest wall.
Lungs
Examine the lungs from central to peripheral. The
lungs will appear whiter when looking from top to bottom because of the increasing thickness of the chest
areas. The lung markings will decrease by thirds as the
viewer goes from central to peripheral. The markings
are also more prominent in the bases of the lungs than
in the upper lung elds.
Compare right and left lung elds, starting at the
top and continuing across and down. Do this in small
segments, evaluating each area carefully. Look for
lesions, lung markings, and density changes such as
areas of opacity (seen in white), which represent consolidation, nodules, and calcications. Note the lung
volume. Decreased volume is seen with atelectasis.
Large-volume lungs with a narrow mediastinum and
a at diaphragm are typically viewed in the patient
with emphysema.
Final Look
Research has shown that there are three high-risk locations where pathology is often missed. They are the
following: the upper lobes of the lungs, costophrenic
areas, and peripheral lung margins. Take one more
look at each of these areas.
The common position for the lateral view is with the
patient’s left chest against the image cassette. The beam
passes from right to left through the patient. Remember
that the right side of the patient is closer to the beam
and therefore structures are magnied on the right side
as compared to the left. The left lateral position is preferred because the heart is less magnied and the bases
of the lungs are more easily seen.
A right lateral image is ordered when the right side
of the lung needs to be less magnied and sharper, such
as when a tumor is suspected. In the lateral position,
the ribs will seem to be superimposed on each other
and the sternum will appear thin.
A good quality lateral image shows lung markings,
ssures (the septa that divide the lobes of the lung),
and good visualization of the spine.
A lateral image can help localize a lesion seen on
the PA view or it may verify lobar consolidation. In
addition, the lateral image allows the viewer to see
behind the sternum and cardiac shadow.
Use a systemic approach when viewing the lateral
image, similar to the PA review.
Anatomy
Review the anatomy of the lateral chest (Figure 37-6).
Vertebral Bodies
The amount of soft tissue is greater at the lung apices
than at the lung bases; therefore, the vertebral bodies appear darker as they approach the diaphragm. Kyphosis is
noticeable on the lateral image. Examine each vertebra
for fractures, and scrutinize the intervertebral disk spaces.
Diaphragm
The right diaphragm is visible and is higher than the
left because of the heart. On the left, the latter two
thirds of the diaphragm should be visible. The gastric
bubble is below the left diaphragm.
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FIGURE 37-6 Lateral chest image. A, unla-
beled B, A diagrammatic overlay showing
the normal anatomic structures numbered or
labeled: 1, tracheal air column; 2, right intermediate brochus; 3, left upper lobe bronchus;
4, right upper lobe bronchus; 5, left interlobar
artery; 6, right interlobar artery; 7, confluence
of pulmonary veins; 8, aortic arch; 9, brachiocephalic vessels. (From Fraser R (ed): Fraser
and Paré’s diagnosis of diseases of the chest,
ed 4, Vol 1, Philadelphia, 1999, Saunders.)
A
Costophrenic Angle
The angle is seen in the most dependent part of the
lung. Both angles should be visible and sharp.
Fissures
Fissures are septa that divide the lobes of lungs. The
major oblique ssure separates the left upper lobe
from the left lower lobe. The right major ssure separates the right upper and middle lobes from the right
lower lobe. The right minor ssure separates the right
upper lobe from the right lower lobe. Fissures are
generally not seen on plain images because their small
surface provides no shadow or interface. However,
these ssures may be seen when pathology occurs in
the lung.
Pleura
Follow the pleura around the lungs from the posterior
costophrenic area to the posterior sternal margin and
posterior ribs.
Retrosternal Area
The retrosternal space is usually dark because of the
presence of air. It is the lower one third of the sternum and appears in contact with the right ventricle.
When this area is seen as opaque, air has been replaced with solid material, and anterior mediastinal
disease should be considered. The area is enlarged
when pulmonary overination occurs, as in emphysema. The retrosternal space will not be visible with
an enlarged heart.
B
Heart/Retrocardiac Area
Identify the right ventricle, left ventricle, and left
atrium. The retrocardiac area of the lateral chest image
is normally dark due to air. If the space is opaque, then
the air has been replaced with an effusion, consolidation, or mass.
Lungs
The scapulae make visualizing the upper lobe difcult
in the lateral image. Lung lesions are often hidden by
the heart on the PA view. Localizing a lesion in the left
lung is best accomplished with the lateral image.
Final Look
Take a last look at each of the areas where lesions are
often missed: the upper lobes, peripheral lung margins,
retrocardiac area, and costophrenic area.
What other imaging studies should
I consider?
Key Questions (to self)
n What other common imaging studies are available
for the chest?
n What imaging studies would give me the best infor-
mation for a particular complaint?
Computed Tomography
Computed tomography (CT), sometimes called computed
axial tomography (CAT), provides a cross-sectional
slice of the area examined. Unlike plain images, which
Chapter 37 • The Chest X-ray 455
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superimpose structures onto an image, a CT scan gives
only one slice. The beams of x-rays pass through the body
in an axial plane as the x-ray tube moves in a continuous
arc around the patient. Detectors are placed opposite the
beam to catch the electrical pulses. The image is the result
of the x-rays that are not absorbed by the tissues between
the beam and the detectors. Detectors pick up the electrical impulses that are fed into a computer that provides the
“picture.” CT is used to distinguish overlapping shadows
from the chest image. It is also very useful in showing ne
details of the pulmonary parenchyma and hilum.
MRI
Magnetic resonance imaging (MRI) produces a
computer-based sectional image that does not use
ionizing radiation. MRI uses the hydrogen molecules in the body to produce the image. A radio frequency pulse transmitted through coils causes some
of the hydrogen molecules to absorb energy and spin
in a different direction from the other hydrogen ions
(resonance). When the radio frequency pulse stops,
the hydrogen molecules stop spinning and release
their excess stored energy. A gradient magnet located inside the main magnet, which provides the
slicing capability of the image, picks up the change.
The results are sent to the computer system, providing a two-dimensional image. MRI of the chest is
used to view lesions of the chest wall and is less
useful for examining the lungs.
PET Scan
Positron emission tomography (PET) scans provide
information on the biochemical metabolism of an organ or tissue. Positrons come from the nucleus of a
proton as it decays to a neutron. When released, the
positron eventually collides with an electron, resulting
in the release of two high-energy gamma photons.
These gamma photons are released at 180 degrees
from each other. The PET scan patient is given a radiotracer that follows the destruction of the positron and
the resulting gamma photons. PET scans are built with
hundreds of detectors on circular rings that are located
directly across from each other. The detectors allow the
localization, in three-dimensional space, of the decay
of the gamma photons. PET scans show the chemical
function of an organ or tissue rather than its structure;
very highly active metabolism is seen with cancer
cells. PET scans are ordered for evaluating the effects
of lung cancer therapy.
Echocardiogram
High-frequency sound waves are directed into the body,
which are then recorded as they deect off organs and
structures. These deections are transmitted back to
a transducer that records the difference in acoustic impedance. This recording is changed into an electrical
signal, which is then analyzed by a computer to produce
an image. Echocardiograms are useful to evaluate heart
size and valvular function.
DIFFERENTIAL DIAGNOSIS OF the Chest Image
WHAT TO LOOK AT NORMAL FINDING ABNORMAL FINDING SUGGESTED CAUSE
Clavicles Midline, symmetrical,
Chest wall Chest wall has
Inspiration Adequate inspiration Less than 10 ribs identified Inadequate inspiration
Vertebral column Straight, equal disk
Ribs All ribs intact
Dark lines; clavicles not
intact
rounded contour
spaces
Able to count 10 ribs
Ribs sloped at edges Ribs horizontal or flattened Hyperinflated lungs, acute asthma,
centered
Sternum pushed outward
(lateral image)
Sternum pushed inward
(lateral image)
Curved Kyphoscoliosis (lateral view); scoliosis
Collapsed disk spaces Degenerative disk disease
Rib fractures present
Less than 10 ribs identified
Fracture; patient rotated; image taken
off center
Pectus carinatum
Pectus excavatum
(PA view)
Trauma
Inadequate inspiration
COPD
Continued
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DIFFERENTIAL DIAGNOSIS OF the Chest Image—cont’d
WHAT TO LOOK AT NORMAL FINDING ABNORMAL FINDING SUGGESTED CAUSE
Trachea Midline Deviation from midline Atelectasis: trachea deviated toward
area of atelectasis; pneumothorax:
air, fluid, tumor, lymph node
enlargement push trachea away from
center; rotated image
Hilar region Normal size, centrally
located
Vascular markings
extend ,1/3 out
into lung field
Bronchi invisible
because air-filled
bronchi have same
density as air in
lungs
Gastric air bubble Present on right Not visible Image placement error; image label
Diaphragm Right higher than
left; right at level of
sixth rib
Costophrenic angle Present, sharp edges Blunted edges or absent Pneumonia, pleural effusion
Visceral pleura Traced around
chest wall
Heart size Cardiac ratio ,50% Cardiac ratio .50% Enlarged heart, patient rotated
Heart borders Presence of heart
borders
Lungs Translucent Fluffy appearance Engorged vasculature
COPD, chronic obstructive pulmonary disease.
Area enlarged Pulmonary artery congestion; lymph
node enlargement
Vascular markings
.1/3 into lung field
Bronchograms present
(bronchi become visible
when lung tissue filled
with fluid is contrasted
with air-filled bronchi)
Infiltrates or consolidation
of lung tissue
Elevated Collapsed lobe or multisegmental
Radiolucent line present
that follows curvature of
diaphragm
Flattened diaphragm Emphysema, asthma, tension
Elevation on left Perforated ulcer or gas distention of
Bilateral elevation Pregnancy, obesity, peritoneal fluid
Hairline shadow, dark black
with no lung markings
Loss of border Infiltrates
Honeycomb appearance Acute respiratory distress syndrome
Butterfly appearance Pulmonary edema
Density changes to
consolidation
Web-shaped density Pulmonary embolism
Bronchopneumonia or pulmonary
congestion
Infiltration; pulmonary edema
Pneumonia
error
collapse; pleural effusion
Free air present
pneumothorax
stomach
Pneumothorax
Bacterial pneumonia
REFERENCES AND READINGS
Dettenmeier P: Pulmonary nursing care, St Louis, 1992, Mosby.
Fraser R, (ed): Fraser and Paré’s diagnosis of diseases of the chest,
ed 4, Vol 1, Philadelphia, 1999, Saunders.
Gaber KA, McGavin CR, Wells IP: Lateral chest x-ray for physicians,
J Royal Soc Med 98:310, 2005.
Kersten L: Comprehensive respiratory nursing: a decision making
approach, Philadelphia, 1989, Saunders.
Landay M: Interpretation of the chest roentgenogram, Boston, 1987,
Little Brown and Co.
Novelline R: Squire’s fundamentals of radiology, ed 5, Cambridge,
Mass, 1997, Harvard University Press.
Tarrac SE: A systematic approach to chest x-ray interpretation in the
perianesthesia unit, J Perianesth Nurs 24:41, 2009.
Wilson S, Thompson J: Respiratory disorders, St Louis, 1990,
Mosby.
C H A P T E R
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38
The Abdominal X-ray
nlike the chest x-ray, the abdominal x-ray is
used primarily for acute conditions and has a
U
the abdominal x-ray will require additional imaging
and the use of contrast radiographic substances to
make structures more visible. Generally abdominal
images are taken to help in diagnosing pain, vomiting, and lack of or abnormal bowel sounds. They are
also useful in nding stones in the kidneys, ureter,
bladder, and gallbladder; ingested foreign objects;
and air distribution. Frequently a chest image is done
at the same time. Every female patient should be
asked if she is pregnant before an image is performed.
DIAGNOSTIC REASONING:
VIEWING THE ABDOMINAL IMAGE
more limited use than the chest x-ray. Often
What are the rst steps in reviewing
the image?
Key Questions (to self)
n Does the image being examined belong to the cor-
rect patient?
n Do I have all views of the area being examined?
n Is the image correctly displayed on the view box or
screen?
n Is the image of good quality?
n Do I know the anatomy of the abdomen?
Image and Patient Identification
As with the chest x-ray, it is important to determine
that the image being viewed is from the patient being
evaluated. Pertinent information about the patient
should be found on the image in the upper corner and
should be veried.
Views
Flat plate or anteroposterior (AP) view. For an
AP view, the patient lies in a supine position on the
x-ray table. A cassette is placed beneath the patient,
with the x-ray machine above the patient. The beam
passes from front to back. The patient is asked to
exhale and the x-ray is taken. Due to the size of the
cassette, a second image may be needed while the patient is in this position to see the entire abdomen from
diaphragm to groin.
Left lateral decubitus view. In a left lateral decubitus image, the x-ray machine moves to a position
where the beam is horizontal to the patient and the left
chest is closest to the image. This view is obtained
when an obstruction or perforation may have occurred,
resulting in free air in the abdomen.
Erect view. For an erect view, an x-ray of the abdomen is taken as the patient is standing. A standing erect
x-ray is used to assess for free air; however, this is seen
only when an excessive amount of air is present.
Chest x-ray. A chest x-ray may be ordered to rule
out free air collection beneath the diaphragm, a pneumonia that may be causing abdominal symptoms, a
pleural effusion, or a subphrenic abscess.
Kidneys, ureter, bladder (KUB). The term KUB
is often used to indicate a at plate of the abdomen. An
x-ray of the kidneys, ureter, and bladder is done to look
for stones or abnormalities.
Image Box Placement
The image, or x-ray lm, is placed on the lightened
view box with the patient’s left side facing the
reader’s right side. The image is labeled with an “R”
or “L” on the bottom. Digital imaging is common
where the x-ray image is viewed on a computer
screen.
Image Quality
The amount of x-ray beamed through the patient
affects the details seen on the image. If too few beams
were delivered, the image will be underexposed
and appear lighter than normal. If too many beams
were delivered, the image will become overexposed
and will be darker than normal. An underexposed
457
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abdominal image is not usually a problem. However,
an overexposed image (darker than normal) requires
a high density spotlight looking for any free air. If
the spine is visible, most other structures should
be seen.
Reviewing Anatomy
Reviewing the normal anatomy of the structures of the
abdomen is helpful when learning how to interpret an
abdominal image. Superimposing the anatomy onto the
image will help to correlate the normal structures
to the shadows. The abdomen, unlike the chest image, is
more difcult to read due to soft tissue organs. A review
of the principles of radiology will help explain this.
Radiodense objects, like bone and calcium, are easy to
see (white). Radiolucent objects, such as air and fat, are
also easy to see (dark). Structures of intermediate density are more difcult to see because they appear gray
(such as solid organs of the abdomen) and gray densities
next to each other are invisible. Organs that have varying densities next to each other (such as the liver border
next to fat) assists in identication. Careful viewing and
knowledge of anatomy is important (Figure 38-1).
What approach should be used when viewing
the image?
Key Questions (to self)
n What is my initial impression?
n Am I using a systematic examination technique?
Initial Impression
When beginning to view the image, it is helpful to ask
why you ordered the image, what you expect to see
based on the history and physical examination, and if
you see it. Initially, view the gas pattern and look for any
extraluminal air, soft tissue masses, or calcications.
Systematic Examination
Systematic examination of the image after an initial overview is mandatory. All parts of the abdominal anatomy
are evaluated at 2 to 4 feet from the image, concentrating
on one part of the image at a time to observe any abnormalities. A suggested systematic examination follows.
DIAGNOSTIC REASONING:
SYSTEMATIC EXAMINATION
How do I assess the AP view?
Bones
Identify the lower rib cage, lumbar spine, sacrum, pelvis, and hip joints. In each instance, look for fracture,
cortical density, and joint and disc space.
Bladder
The inferior aspect of the bladder projects 5-10 mm
above the symphysis pubis. If the bladder is full, it will
appear as a soft tissue density in the pelvis (Figure 38-2).
flexure
Liver
Gallbladder
Ascending
colon
Small
intestine
Appendix
FIGURE 38-1 Normal abdominal anatomy. (From Seidel HM,
Ball JW, Dains JE, Flynn J, Solomon B, Stewart R: Mosby’s
guide to physical examination, ed 7, St Louis, 2011, Mosby.)
Spleen
Stomach
Transverse
colon
Descending
colon
Sigmoid
colon
Bladder
Hepatic
flexure
Transverse
colon
Descending
colon
Ascending
colon
Bladder
FIGURE 38-2 Supine abdominal radiograph showing co-
lon, bladder, and flexures. (Modified from Johns Hopkins
University, Piccini J, Nilsson K [eds]: The Osler medical
handbook, ed 2, Philadelphia, 2006, Saunders.)
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Uterus
The uterus sits on top of the bladder, possibly indenting
the bladder, and is often not seen on plain x-ray.
Liver
Observe for homogeneous density in the right upper
abdominal quadrant. The lower border of the liver is
found in the right ank near the right costal margin.
The adjacent fat provides the contrast showing the
liver edge (Figure 38-3).
Spleen
The spleen is found in the left upper quadrant between
the diaphragm and fundus of the stomach. It is the size
of the adult st and is usually not seen. Because the
spleen must be very enlarged to be seen, ultrasound
may be more benecial (see Figure 38-3).
Psoas Muscle
The psoas muscle shadows are visible as diverging lines
on both sides of the spine starting from the rst lumbar
vertebra towards the pelvis (see Figure 38-3).
Kidneys
The kidneys are retroperitoneal organs that are visualized on the x-ray due to the presence of perirenal fat.
Visualization may be obscured by bowel loops. The
left kidney is higher than the right. The shadow
should appear smooth with the superior pole closest
to the midline. Kidneys are located on either side
of the lower thoracic and upper lumbar spine between
the upper border of the eleventh thoracic vertebra
and the lower border of the third lumbar vertebra (see
Figure 38-3).
Stomach
The stomach can be identified in its location above
the transverse colon by the bandlike shadows of the
gastric rugae in the supine view, and by the
gas fluid level beneath the left hemidiaphragm in
the erect view. When supine, air in the stomach
will rise anteriorly and fluid will pool posteriorly
(Figure 38-4).
Colon
The colon often has a bubbly appearance representing a
mixture of gas and fecal material. It lies on the periphery of the abdomen and may be lled with air or feces.
The colon begins at the hepatic exure and goes to the
rectum. Fecal matter in the bowel gives a “mottled” appearance. This is seen as a mixture of grey densities
representing a gas liquid-solid mixture (Figure 38-5).
A mechanical obstruction causes the large bowel to
become dilated .6 cm. The dilated colon is above the
FIGURE 38-3 Supine abdominal radiograph showing kidneys,
spleen, liver, and psoas muscle. (Modified from Johns Hopkins
University, Piccini J, Nilsson K [eds]: The Osler medical hand-
book, ed 2, Philadelphia, 2006, Saunders.)
Spleen
Liver
Left kidney
Right
kidney
Psoas
muscles
Spleen
Right
kidney
Gas in
stomach
Left
kidney
Right psoas
muscle
Left psoas
muscle
Tip of
liver
FIGURE 38-4 Normal gas in the stomach. (From Mettler F:
Essentials of radiology, ed 2, Philadelphia, 2005, Elsevier.)
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FIGURE 38-5 Constipation. (From Walsh T, Caraceni A,
Fainsinger R, Foley K, Glare P, Goh C et al: Palliative medicine, Philadelphia, 2009, Elsevier.)
obstruction and no air in the colon appears below the
point of obstruction (Figure 38-6). A paralytic ileus
(post surgery) shows a bowel that is dilated but has
gas throughout the small and large intestine with no
delineation.
Small Bowel
The small bowel lies in the center of the abdomen
within the “frame” of the large bowel; often little
small bowel is seen on the image. The normal small
bowel diameter should not exceed 3 cm. A small
bowel obstruction presents as multiple dilated loops in
the central abdomen with no air in the large bowel
(Figure 38-7).
Calcifications
Whiteness of calcifications is due to the absorption
of the x-rays. Calcifications seen in the pancreas,
kidney (Figure 38-8), gallbladder, and aorta are
abnormal. Occasionally one may see a calcification
in the area of the appendix called an appendicolith.
In women, fibroids may become calcified and
visible.
FIGURE 38-6 Mechanical large bowel obstruction. (From
Herring W: Learning radiology: recognizing the basics,
St Louis, 2007, Elsevier.)
Gas Patterns/Extraluminal Air
Air is naturally swallowed and can be seen in the stomach. When a patient is in the supine position, the gas
will rise to the anterior portion of the stomach. Gas in
the small bowel is located in the left midabdomen and
the lower central abdomen. Gas in the colon often has
a bubbly appearance representing a mixture of gas and
fecal material. Gas within the peritoneal cavity outside
the sealed gastrointestinal tract is abnormal and is
termed pneumoperitoneum (Figure 38-9).
Artifacts
Artifacts may be immediately obvious. Piercing of the
umbilicus is very popular, especially in young women;
genital piercing is not infrequent. Metallic objects are
obvious. There may be clips or materials from previous
surgeries.
If my patient has abdominal pain, what other
x-ray should I consider?
Key Question (to self)
n What are the indications for ordering other x-rays?
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