Analysis of abdominal X-ray: A simple technique but full of information.

66 Pages·2015·10.67 MB·English

Analysis of abdominal X-ray: A simple technique but full of
information.
Poster No.: C-2157
Congress: ECR 2015
Type: Educational Exhibit
Authors: P. Servent Sáenz; Majadahonda/ES
Keywords: Abdomen, Anatomy, Conventional radiography, Diagnostic
procedure, Education, Image compression, Education and training,
Image verification
DOI: 10.1594/ecr2015/C-2157
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Page 1 of 66
Learning objectives
LEARNING OBJECTIVES:
• Recognising common structures and densities that we can find in abdominal
X-ray.
• Knowing the abdominal X-ray projections that should be taken and when
they are indicated.
Background
BACKGROUND:
Abdominal X-ray is the first imaging technique that is taken in a patient with abdominal
pain. This imaging technique shows us an abdominal panoramic view with a lot of
information without any type of contrast enhanced or patient preparation.
That is the reason why, is significant to know: when it is it indicated, which projections
should be taken and more importantly, is normal what I´m looking at.
To answer each of these questions, we will show different protocols and projections that
should be taken as clinical suspicion and systematic approach to be done to recognize
normal structures that are objectified in abdominal X-ray.
Findings and procedure details
FINDINGS AND PROCEDURE DETAILS:
The standard protocol for taking an X-ray depends on clinical suspicion. Systematic
approach should always be the same for not losing any detail of the abdominal cavity.
Therefore, we will divide the interpretation of abdominal X-ray as a checklist.
1. WHEN IS ABDOMINAL X-RAY INDICATED?
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• Abdominal plain radiography should be the first diagnostic modality used
with patients with acute abdomen:
- Suspicion of a perforated viscera.
- Suspicion of a bowel obstruction.
- Investigation of foreign bodies.
• May be useful in:
- Initial study of renal colic.
- Prior to performing barium contrast examination.
2. WHICH PROJECTION SHOULD BE TAKEN?
An important aspect is the knowledge of the different projections that can be taken and
its diagnostic utility. These are the principal projections:
• Antero-posterior (AP) supine projection Plain abdominal radiography.
Fig. 1 on page 15
- This is the most frequently projection taken.
- It must extend from the diaphragm to the symphysis pubis.
- It provides maximum detail of radiological anatomy and pathology.
• AP erect projection. Fig. 2 on page 16
- To demonstrate fluid levels.
- It may confirm a pneumoperitoneum, when gas has risen to the classic
subdiaphragmatic position.
• Left decubitus with horizontal beam projection. Fig. 3 on page 17
- Beam parallel to the table.
- To realize this projection is necessary to wait 5 or 10 minutes with the patient in the
lateral decubitus position so that the gas is properly placed.
- Its purpose is to obtain further information, such as confirmation of a small amount of
free gas.
-To demonstrate fluid levels in a patient too ill to be sat up.
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• Supine decubitus with horizontal beam projection. Fig. 4 on page 18
- Patients who are not able to mobilize and a perforation is suspected.
• It is important to take a chest X-ray Fig. 5 on page 19 as a
complementary projection because:
- There are thoracic disorders with symptoms referred to the abdomen (eg.
pneumonia ...).
- Pneumoperitoneum can be visualized as free air under the diaphragm. Fig. 6 on page
20
The knowledge of different projections is important because if we suspect disease and
do not take the proper projection some pathology can be masked. For this reason, there
are different protocols with different projections based on clinical suspicion. Table 1 on
page 21
Table 1: Table with different protocols and projections based on clinical suspicion.
Page 4 of 66
References: Radiology, Hospital Universitario Puerta de Hierro - Majadahonda/ES
• Suspicion of a bowel obstruction:
- AP supine X-ray.
- Chest X-ray.
- AP erect X-ray.
- Supine X-ray with horizontal beam.
- Lateral X-ray (study of rectal gas).
• Suspicion of a bowel perforation:
- AP supine X-ray.
- Chest X-ray.
- AP erect X-ray.
- Left decubitus with horizontal beam X-ray.
• Investigation of foreign bodies.
- Serial radiographies with AP supine projection.
• Initial study of renal colic.
- AP supine X-ray.
3. IS IT NORMAL WHAT I´M LOOKING AT?
To answer this question it is very important to take a systematic approach for not losing
any detail of the abdominal cavity. Therefore, we will divide the interpretation of abdominal
X-ray as a checklist.
1. Evaluating the outlines of major abdominal organs and abdominal muscles
(fat lines).
2. Abdominal gas analysis.
3. Search calcified structures.
4. Study of the skeleton.
5. Finding foreign bodies.
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Before starting the systematic approach, it is worth knowing the five basic densities that
are normally present on X-rays, which appear thus Fig. 7 on page 22 , Table 2 on
page 23 :
Table 2
References: Radiology, Hospital Universitario Puerta de Hierro - Majadahonda/ES
• Gas = Black: normally it is visualized in the digestive tract.
• Fat = Dark Grey: intermediate density between air and water. It is visualized
for example as the outline of muscles or solid viscera.
• Soft tissue/fluid = Light grey: viscera, solid structures or soft tissues (liver,
kidneys, muscles, bladder...).
• Bone/calcification = White: The lowermost ribs, gallstones, Pelvic
phleboliths.
• Metal = Intense white: surgical clips, zipper pants...
3.1 Evaluating the outlines of major abdominal organs: Fig. 8 on page 24
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Fig. 8: Outlines of major abdominal organs.
References: Radiology, Hospital Universitario Puerta de Hierro - Majadahonda/ES
• Liver outline: Fig. 9 on page 25
- Angle between the lower and outer edge of the right hepatic lobe.
- When the liver outline extends toward the iliac crest is called Riedel lobe. Fig. 10 on
page 26
- When the transverse colon is interposed between the liver and the diaphragm is called
Chilaiditi´s sign that can simulate a bowel perforation. Fig. 11 on page 27
• Splenic outline: Fig. 12 on page 28
- It corresponds to the lower pole of the spleen.
- The distance between the diaphragm and spleen outline indicates the splenic length.
• Kidneys outline: Fig. 13 on page 29
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- They are visible due to perirenal fat that surrounds them.
- Kidney major axis is parallel to the psoas muscle.
• Bladder outline: Fig. 14 on page 30
- The whole bladder is visualized, but especially the upper edge.
- On both sides of the bladder are paravesical spaces that are taken up by small bowel.
3.2 Evaluating the outlines of abdominal muscles Fig. 15 on page 31
Fig. 15: Outlines of abdominal muscles.
References: Radiology, Hospital Universitario Puerta de Hierro - Majadahonda/ES
• Psoas muscles outlines Fig. 16 on page 32
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- They form diverging interfaces extending inferolaterally from the lumbar spine to insert
on the lesser trochanters of the femora.
- Their non-visualization should be interpreted with caution, because there are many
reasons why they may not be visible, such as an excess of overlying gas, increased
abdominal fat…
• Properitoneal or flank muscles outlines Fig. 17 on page 33
- They correspond to interfaces between layers of muscles and fat of lateral abdominal
wall.
• Lesser pelvis muscles outlines Fig. 18 on page 34
- These outlines are more prominent in children and young people and less pronounced
or absent in adults.
- They correspond to internal obturator muscle and levator ani muscle.
3.3 Abdominal gas analysis:
Under normal conditions, in an abdominal plain radiography is common to find air within
the hollow viscera. Therefore, any structure outlined by gas in the abdomen will be part
of the gastrointestinal tract.
There is a rule that we should know: the 3-6-9 rule. Fig. 19 on page 35
This rule is useful to remember the maximum diameter accepted for different segments
of the digestive tract. Thus, normal small bowel diameter is less than 3 cm, the colon
diameter less than 6 cm and cecum less than 9 cm.
Intraabdominal gas distribution typically has the following features:
• Stomach:
- Gastric air bubble appears immediately below the diaphragm and inside the splenic
flexure of the colon and crosses across the spine around the lowermost thoracic or upper
lumbar vertebrae. Fig. 20 on page 36
- Is important to know that the stomach liquid content is located in the fundus creating a
circular contour, the "gastric pseudotumor". Fig. 21 on page 37
• Small bowel:
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- We found small air bubbles in some section of the small bowel as small bubbles that
adapt to the morphology of conniventes valves along the abdominal cavity especially in
the center of the abdomen. Fig. 22 on page 38
- A clue to recognize what intestinal segment we are seeing, remember that valvulae
conniventes are more numerous in the jejunum than ileum. Fig. 23 on page 39
• Large bowel/Colon:
- Usually, in all abdominal plain radiographs, air is in every segment of the colon, including
the rectum . Fig. 24 on page 40
- It is important to keep in mind that retroperitoneal sections of the colon (ascending
colon, descending colon and rectum) usually have a constant position so we can identify it
better than intraperitoneal sections (transverse colon and sigmoid colon), with a variable
position. Fig. 25 on page 41
- Another characteristic feature of large bowel is that it contains faeces. Fecaloid remains
have a mottled appearance due to its gaseous part content. Fig. 26 on page 42
3.4 Search calcified structures.
They are frequent findings in abdominal plain radiography that usually lack clinical
significance.
3.4.1 By their morphological appearance we can divide abdominal calcifications in four
groups: Fig. 27 on page 43
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