An introduction to abdominal radiograph interpretation for medical students.

1. Approaching the PFA
David Murphy FRCR, FFRRCSI
Radiology SpR
St Vincent’s University Hospital
Dublin, Ireland

2. Terminology
PFA=Plain Film of the Abdomen
AXR=Abdominal X-Ray

3. Terminology
PFA=Plain Film of the Abdomen
AXR=Abdominal X-Ray
These terms are interchangeable!

4. Technique
Nearly all PFAs are now acquired as supine antero-
posterior (AP) radiographs
Erect PFAs are not routinely performed anymore in adults
Lateral decubitus (patient lying on their side) abdominal x-
rays are rarely performed in adults-occasionally in children

5. Radiation Dose
Average radiation dose for a PFA is 0.7mSv (Sieverts).
Approximately 35 times the dose of a standard chest x-ray
(CXR), which is 0.02mSv.
Portable PFAs are not routinely performed due to the
problem of radiation dose to surrounding patients

6. Indications
Suspected bowel obstruction
Suspected bowel perforation (along with an erect CXR)
Suspected abdominal mass
Ingested foreign body
Evaluation of possible toxic megacolon
Follow up of renal tract calculi

7. PFA is not routinely indicated
in…
Vague abdominal pain
Constipation
Uncomplicated appendicitis
Gastroenteritis
Haematemesis

8. Normal Structures Visible on
PFA
Gas in stomach, colon, rectum +/- small bowel
Renal outlines
Outline of right lobe of liver
+/- outline of spleen
Psoas shadows
Costal margin, lumbar vertebrae, pelvic bones

9. Bowel gas pattern
Any part of the bowel will be visible if it contains gas in the
lumen
Upper limit of normal for bowel diameter -3/6/9 rule
1. 3cm - Small Bowel
2. 6cm - Large Bowel
3. 9cm - Caecum

10. Stomach
May be visible if it contains
gas/fluid
Usually visible in the left
upper quadrant
Can cross the midline
May see pattern of gastric
rugae
Rugae

11. Small bowel
Usually central in the
abdomen
Has valvulae conniventes
(arrows) that cross the
entire width of the small
bowel
Normally <3cm in diameter

12. Large Bowel
Peripheral position
Has incomplete transverse
folds called haustra (arrow)
Contains faeces
Large bowel should be
<6cm, caecum <9cm

13. Liver
Lies in the RUQ
Superior portion forms the
right hemidiaphragm
contour
Gallbladder not usually
visible (can see gallstones
if calcified, 10-20% of
cases)

14. Kidneys
Often visible on PFA
Lie at T12-L3
Lateral to psoas muscles
Right kidney slightly lower
due to liver
T12
L1
L2
L3
Psoas
outline

15. Normal Bones Visible
Sacrum
Iliac
bone
Femoral
head
T12
L1
L2
L3
L4
L5
11th and 12th ribs
Acetabulum
Superior
pubic
ramus

16. Normal PFA

17. Normal PFA-Liver & Spleen

18. Normal PFA-Kidneys

19. Normal PFA- Psoas
shadows

20. Normal PFA-Colon

21. Interpretation
Major areas to assess on the PFA:
1. Bowel gas pattern
2. Soft tissues
3. Bones
4. Calcifications

22. 10 practice cases
Read the history, look at the
PFA and try and formulate a
differential diagnosis before
clicking ahead

23. Case 1
60 year old man with
abdominal pain, distension and
vomiting

25. 1. Mechanical Small bowel
obstruction
Multiple air filled dilated
loops of bowel in the center
of the abdomen with
valvulae conniventes

26. 1. Mechanical Small bowel
obstruction
Coronal CT confirms
mechanical small bowel
obstruction.

27. 1. Mechanical Small bowel
obstruction
Coronal CT confirms
mechanical small bowel
obstruction.
Axial CT shows the site of
obstruction (zone of
transition, arrow) in the right
iliac fossa.
Obstruction caused by ileal
stricture from Crohn’s
disease.

28. Case 2
78 year old man with sudden
onset severe abdominal pain

30. 2. Perforation
Multiple dilated loops of
large bowel
Generalised central
lucency in the abdomen
Air underneath the liver,
outlining the falciform
ligament (arrow)

31. 2. Perforation
Zoomed up image of the
right upper quadrant
shows air outlining both
sides of the bowel wall
(arrows)
Allows for exact deliniation
of the bowel wall
Called Rigler’s sign-very
sensitive for perforated
large or small bowel
CT confirmed perforation
due to a colonic tumour

32. Case 3
80 year old woman with
abdominal pain and distension

34. 3. Sigmoid Volvulus
Large dilate loop of large
bowel centered in the
pelvis
Has an inverted U
configuration, with its axis
pointed towards the right
upper quadrant (arrow)
Dilated loops of large
bowel are seen in the left
upper quadrant
Also note the EVAR stent

35. 3. Sigmoid Volvulus
This appearance is often
called the coffee bean
appearance and is typical
for a sigmoid volulus

36. 3. Sigmoid Volvulus
Coronal CT shows the
swirled sigmoid mesentery
around which the sigmoid
colon has twisted (arrows)
This is called the whirlpool
sign

37. Case 4
50 year old man with painless
abdominal swelling and a
history of alcohol excess

39. 4. Ascites
General paucity of aerated
bowel loops
Homogenous increased
density throughout the
abdomen
Visible bowel loops tend to
be in the centre of the
abdomen (imagine them
floating!)

40. 4. Ascites
CT shows a shrunken,
nodular liver consistent
with cirrhosis with large
volume ascites
Note the calcified
gallstones (arrow)-Did you
spot them on the PFA?

41. Case 5
80 year old woman with a
painless, pulsatile abdominal
mass

43. 5. Abdominal Aortic Aneurysm
There is round structure in
the lower abdominal
midline with faint
peripheral calcification
(arrows)
Classical appearance of an
abdominal aortic aneurysm
(AAA) on PFA with mural
calcification

44. 5. Abdominal Aortic Aneurysm
CT angiogram confirms the
presence of the large
infrarenal AAA (arrows)
Significant amount of
thrombus (low density
material) within the
aneurysm sac

45. 5. Abdominal Aortic Aneurysm
3D reconstructions shows
the relationship of the
aneurysm to the kidneys
and can help with
operative planning

46. Case 6
60 year old man with difficulty
urinating and severe back
pain

48. 6. Bone Metastases
There is a generalised
increased density of the
pelvic bones and lumbar
spine (compare the density
to the previous PFAs)
Appearances are those of
diffuse sclerotic bone
metastases

49. 6. Bone Metastases
Sagittal whole spine CT
confirmed diffuse bone
sclerosis
Classical appearance of
prostate cancer with
diffuse sclerotic osseous
metastases
Always check the bones
on a PFA!

50. Case 7
70 year old woman with
severe abdominal pain

52. 7. Bowel ischaemia
Generalised increase in
lucency with positive
Rigler’s sign in the RUQ
and free air under the right
hemidiaphragm consistent
with perforation

53. 7. Bowel ischaemia
Close up of large bowel
loops in the RIF shows
bubbles of gas within the
bowel wall (arrows),
known as pneumatosis

54. 7. Bowel ischaemia
Close up of large bowel
loops in the RIF shows
bubbles of gas within the
bowel wall (arrows),
known as pneumatosis
Pneumatosis is highly
suggestive of ischaemic
bowel

55. 7. Bowel ischaemia
CT abdomen on lung
windows (to look for air)
shows bubbles of gas
within the bowel wall,
confirming pneumatosis.
Bowel ischaemia was
confirmed at surgery.

56. Case 8
65 year old woman with
altered bowel habit

58. Case 8
Nonspecific bowel gas
pattern
No cause for the patient’s
acute symptoms is
identified

59. 8. Splenic Artery
Aneurysms
Did you spot the several
peripherally calcified
lesions in the left upper
quadrant? (arrow)
This appearance is typical
of multiple splenic artery
aneurysms

60. 8. Splenic Artery
Aneurysms
CT confirmed the presence
of multiple peripherally
calcified splenic artery
aneurysms at the splenic
hilum
Important diagnosis as
they are prone to rupture,
especially during
pregnancy.

61. Case 9
50 year old man with chronic
lower back pain

63. 9. Sacral tumour
There is a large lytic,
expansile, destructive
abnormality in the sacrum
(arrow) consistent with a
tumour.
The foreign body in the left
lower quadrant is a spinal
cord stimulator to help
treat chronic pain

64. 9. Sacral tumour
Coronal CT abdomen on
bone windows confirms
the large destructive soft
tissue mass in the sacrum
(arrow)
Biopsy confirmed a
primary bone tumour

65. Case 10
60 year old woman with
abdominal pain and reduced
mobility

67. Case 10
At first look this PFA looks
normal
Do you spot any
abnormality?

68. Case 10
Always look at the edge of
the film

69. 10. Displaced Left Femoral
Fracture
The left femoral shaft is in
an abnormal position

70. 10. Displaced Left Femoral
Fracture
Pelvic X-ray shows an old
non-united left femoral
neck fracture with superior
migration of the left
femoral shaft (arrow).
Always look at the edge of
the x-ray for ‘hidden’
abnormalities, especially
in exams!

71. Summary
Major areas to look at on the PFA:
1. Bowel gas pattern (3/6/9 rule)
2. Soft tissues
3. Bones
4. Calcifications
Always look at the edges of an x-ray for ‘hidden’
abnormalities

72. svuhradiology.ie
David Murphy FRCR, FFRRCSI
Radiology SpR
St Vincent’s University Hospital
Dublin, Ireland