Introduction to Clinical Radiology
Introduction to Abdominal Radiology
Bruce P. Brown, M.D.
Peer Review Status: Not Peer Reviewed
Normal "FIat Plate" (KUB) of the abdomen
Abdominal plain film is often the starting point for the work up
of abdominal problems. An abdominal
CT can give you an idea how the flat plate is taken. The most
common clinical question is obstruction vs. adynamic ileus, so it is
important to be able to recognize both of these.
Bowel gas pattern
The gas provides a natural contrast within the intestines which is
very useful in detecting abdominal disease.
Where is the appearance of gas normal?
- Gas is usually present in stomach.
- The small bowel may be partially filled with gas.
- Gas may also be seen throughout the entire colon.
Normal Gas Pattern
Soft tissue/visceral outlines
The outlines of soft tissue is made possible by radiolucent fat which
surrounds intra-abdominal organs.
This allows for visualization of the following:
- Liver - posterior margin visible where outlined by
retroperitoneal fat.
- Spleen - often visible
- Kidneys - outlines may not be seen in entirety because of
overlying gas and stool
- Psoas muscles - margins usually visible but may not be seen in
entirety
Normal KUB
These structures may not always be visible. Technical problems, such
as overlying bowel gas, may obscure the liver's edge. In isolation, a
missing psoas margin may be irrelevant but in the context of the
patient's history or examination it may be very significant.
There are a number of indications for requesting abdominal
films:
- Bowel obstruction - abnormal gas pattern
- Free air - abnormal gas pattern
- Calculi or other abnormal intra-abdominal calcifications
- Abscess - abnormal gas pattern
- Radiopaque foreign bodies
Abnormal bowel gas patterns
Too much gas
An increase in abdominal gas may be due to three complications:
- Adynamic ileus -
leads to increased gas throughout the Gl tract, multiple air-fluid
levels, and gas in the rectum.
- Mechanical small bowel
obstruction - leads to a ladder-like arrangement of
dilated small bowel loops, also termed a "stacked coin"
appearance. There is very little or absent gas in the colon.
- Mechanical large bowel
obstruction - leads to a distended colon but absence of
gas in rectum and/or distal colon, +/- small bowel distension.
Gas in the wrong location
- Free intraperitoneal air
(pneumoperitoneum) - MUST have either an upright or left
lateral decubitus view, will see a crescent of air under the
diaphragm or outlining the liver.
- Abscess - gas does not
conform to a bowel loop in appearance or location, is persistent
over time and with change of position.
- Ascites - small bowel loops
are displaced to the center of the abdomen, "ground glass"
appearance to abdominal contents.
- Other - emphysematous
pyelonephritis, portal vein gas,
gas in the binary system.
Absence of gas
- Fluid filled loops of bowel
- Abnormal mass
Abnormal soft tissues
"Normal" calcifications
Bones are the only normal calcified stnuctures. However, many other
calcifications will be seen that have no clinical significance.
- Vascular-veins of the pelvis (phleboliths)
- Costal cartilage
- Lymph nodes
- Granulomas
- Injection sites
Abnormal calcifications
- "Stones" - renal calculi, cholelithiasis, bladder
calculi, appendiciolith
- Vascular-calcifications, aneurysm
- Pancreatic-chronic pancreatitis
- Leiomyoma (uterine fibroid)
- Tumor calcification
- Other
Foreign bodies
Abnormalities of bone
The topic will be covered in more detail in the skeletal lecture
Abnormalities visible on a flat film include:
- Metabolic disease
- Arthritis
- Trauma-fractures
- Remember that a fractured bone may also have related soft
tissue injuries:
- A fracture of the left lower ribs may damage the spleen.
- A fracture of the transverse process of a lumbar vertebra
may damage the ureter.
- A fracture of the pelvis may tear the urethra and/or
rupture the bladder.
- Pelvic Fracture
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