Abdomen xray signs

1. Abdominal X-ray Radiological Signs
Suzanne O’Hagan

2. Lightbulb moment
a moment of sudden inspiration, revelation, or recognition

3. Approach to AXR
• Bowel gas pattern
• Extraluminal air
• Soft tissue masses
• Calcifications

4. Normal AXR
11th
rib
Hepatic flexure
Gas in
stomach
T12
Gas in caecum
Iliac crest
Femoral head
SI joint
Gas in sigmoid
Transverse colon
Splenic flexure
Psoas margin
Sacrum
Left kidney
Liver
Bladder

5. Gas pattern
• Stomach
– Almost always air in stomach
• Small bowel
– Usually small amount of air in
2 or 3 loops
• Large bowel
– Almost always air in rectum
and sigmoid
– Varying amount of gas in rest of large bowel
What is normal?

6. Normal fluid levels
• Stomach
– Always (upright, decub)
• Small bowel
– Two or three levels
acceptable (upright, decub)
• Large bowel
– None normally
(functions to remove fluid)

7. Large vs small bowel
• Large bowel
– Peripheral (except RUQ occupied by liver)
– Haustral markings don’t extend from wall to wall
• Small bowel
– Central
– Valvulae conniventes extend across lumen and are
spaced closer together

8. Radiographic principles
Series of films for acute abdomen
• Obstruction series/ Acute abdominal series/
Complete abdominal series
– Supine (almost always)
– Upright or left decubitus (almost always)
– Prone or lateral rectum (variable)
– Chest, upright or supine (variable)

9. VIEW LOOK FOR
SUPINE ABDOMEN Bowel gas pattern
Calcifications
Masses
PRONE ABDOMEN Gas in rectosigmoid
Gas in ascending and
descending colon
UPRIGHT ABDOMEN Free air, air-fluid levels
UPRIGHT CHEST Free air, lung pathology
secondary to intraabdominal
process
Acute abdominal series
What to look for
Substitutes: Prone Lateral rectum
Upright Left lateral decub
Upright chest Supine chest

10. Obtaining views
• Supine
– Patient on back, x ray beam directed
vertically downward, casette
posterior, x-ray tube anterior (AP)
• Prone
– Patient on abdomen, x-ray beam
directed vertically downward, cassette
anterior, x-ray tube posterior (PA)
• Upright
– Patient stands or sits, x-ray beam
directed horizontally, cassette
posterior, x-ray tube anterior (AP)
• Upright chest
– Patient stands or sits, horizontal x-ray
beam, cassette anterior, x-ray tube
posterior (PA) 1900s X-Ray-based fluoroscopy machine
in which radiation is shot directly through
the patient and into the doctor’s face.

11. Abnormal Gas Patterns
• Functional ileus
– One or more bowel loops become aperistaltic usually
due to local irritation or inflammation
• Localised “sentinel loops” (one or two loops)
• Generalised (all loops of large and small bowel)
• Mechanical obstruction
– Intraluminal or extraluminal
• Small bowel obstruction
• Large bowel obstruction

12. 3, 6, 9 RULE
Maximum Normal Diameter of bowel
Small bowel 3cm
Large bowel 6cm
Caecum 9cm

13. Localised ileus
Key features
• One or two persistently dilated
loops of small or large bowel
(multiple views)
• Often air-fluid levels in sentinel
loops
• Local irritation, ileus in same
anatomical region as
pathology
• Gas in rectum or sigmoid
• May resemble early SBO

14. Causes of Localised Ileus
by location
SITE OF DILATED LOOPS CAUSE
Right upper quadrant Cholecystitis
Left upper quadrant Pancreatitis
Right lower quadrant Appendicitis
Left lower quadrant Diverticulitis
Mid-abdomen Ulcer or kidney/ureteric calculi

15. Colon cut off sign
Explanation:
Inflammatory exudate in acute
pancreatitis extends into the
phrenicocolic ligament via lateral
attachment of the transverse
mesocolon
Infiltration of the phrenicocolic
ligament results in functional
spasm and/or mechanical
narrowing of the splenic flexure at
the level where the colon returns
to the retroperitoneum.
Abrupt cutoff of colonic gas column at the splenic flexure (arrow). The colon is
usually decompressed beyond this point.

16. Generalised ileus
Key features
• Entire bowel aperistaltic/hypoperistaltic
• Dilated small bowel and large bowel to rectum
(with LBO no gas in rectum/sigmoid)
• Long air-fluid levels
CAUSE REMARK
*Postoperative Usually abdominal surgery
Electrolyte imbalance Diabetic ketoacidosis
* almost always

17. Generalised adynamic ileus
The large and
small bowel are
extensively airfilled
but not dilated.
The large and
small bowel "look
the same".

18. Mechanical SBO
• Dilated small bowel
• Fighting loops (visible loops, lying
transversely, with air-fluid levels at different
levels)
• Little gas in colon, especially rectum

19. SBO Erect SBO Supine
Air fluid levels

20. Causes of Mechanical SBO
* May be visible on AXR
Adhesions
Hernia*
Malignancy
Gallstone ileus*
Intussesception
Inflammatory bowel disease

21. Step ladder appearance
• Loops arrange
themselves from
left upper to
right lower
quadrant in
distal SBO

22. Coil spring sign

23. String of pearls sign
Considered diagnostic of obstruction (as opposed to ileus)
and is caused by small bubbles of air trapped in the
valvulae of the small bowel.

24. Stretch/slit sign
Slit of air caught in a
valvulae, characteristic
of SBO

25. Closed loop obstruction
• Two points of same loop of bowel obstructed
at a single location
• Forms a C or a U shape
– Term applies to small bowel, usually caused by
adhesions
– Large bowel, called a volvulus

26. Crescent Sign
Caused by:
LUQ Soft tissue mass
OR
Head of intussusception
in distal transverse colon

27. Double Bubble Sign
Duodenal Atresia

28. Mechanical LBO
• Colon dilates from point
of obstruction
backwards
• Little/no air fluid levels
(colon reabsorbs water)
• Little or no air in
rectum/sigmoid

29. Large bowel obstruction
Bowel loops tend not to
overlap therefore
possible to identify site
of obstruction
Little or no gas in small
bowel if ileocaecal valve
remains competent*
* If incompetent, large bowel
decompresses into small bowel, may
look like SBO

30. Causes of Mechanical LBO
TUMOUR
VOLVULUS
HERNIA
DIVERTICULITIS
INTUSSUSCEPTION

31. Note on volvulus
• Sigmoid colon has its own mesentry therefore
prone to twisting
• Caecum usually retroperitoneal and not prone
to twisting; 20% people have defect in
peritoneum that covers the caecum resulting
in a mobile caecum

32. Volvulus
A volvulus always extends away from the area of twist.
Sigmoid volvulus can only move upwards and usually
goes to the right upper quadrant. Caecal volvulus
can go almost anywhere.

33. Coffee Bean Sign
Sigmoid volvulus
Massively
dilated
sigmoid loop

34. Hernia
Lateral decubitus of value
The advantage is that there may be a greater chance of air entering the
herniated bowel because it is the least dependent part of the bowel in the
supine position.

35. Apple core sign
• Radiologic manifestation of a
focal stricture of the bowel
usually at contrast material
enema examination. The
stricture demonstrates
shouldered margins and
resembles the core of an
apple that has been partially
eaten. The most common
cause is an annular carcinoma
of the colon.

36. Thumbprinting
The distance between
loops of bowel is increased
due to thickening of the
bowel wall.
The haustral folds are very
thick, leading to a sign
known as 'thumbprinting.'

37. Lead pipe
colon
• Shortening of
colon secondary
to fibrosis
• Loss of
haustration
• Ulcerative colitis

38. Extraluminal air
• TYPES
– Pneumoperitoneum/free air/intraperitoneal air
– Retroperintoneal air
– Air in the bowel wall (pneumatosis intestinalis)
– Air in the biliary system (pneumobilia)

39. Upright film best
• The patient should be positioned sitting
upright for 10-20 minutes prior to acquiring
the erect chest X-ray image.
• This allows any free intra-abdominal gas to
rise up, forming a crescent beneath the
diaphragm. It is said that as little as 1ml of gas
can be detected in this way.

40. Free Air
Causes
• Rupture of a hollow viscus
– Perforated peptic ulcer
– Trauma
– Perforated diverticulitis (usually seals off)
– Perforated carcinoma
• Post-op 5-7 days normal, should get less with successive
studies *NOT ruptured appendix (seals off)

41. Signs of free air
• Crescent sign
• Chilaiditis sign
• Riglers (and False Rigler’s)
• Football sign
• Falciform ligament sign
• Triangle sign
• Cupola sign
• Lesser sac sign

42. Crescent Sign II
Free air under the diaphragm
Best demonstrated on
upright chest x rays or
left lat decub
Easier to see under
right diaphragm

43. Chilaiditis sign
• May mimic air under
the diaphragm
• Look for haustral folds
• Get left lat decub to
confirm
In patients who have cirrhosis
or flattened diaphragms due to
lung hyperinflation, a void is
created within the upper
abdomen above the liver. This
space may be filled by bowel. If
this bowel is air filled then it
may mimic free gas.

44. Rigler’s Sign
Bowel wall visualised on both sides due to intra and extraluminal air
Usually large amounts of free air
May be confused with overlapping loops of bowel, confirm with upright view

45. False Rigler’s Sign
• The Rigler sign can sometimes be simulated by
contiguous loops of bowel, whereby
intraluminal air in one loop of bowel may
appear to outline the wall of an adjacent loop,
which results in a misdiagnosis of free air.
• Measure distance of interface if unsure

46. Football SIgn
Seen with massive
pneumoperitoneum
Most often in children
with necrotising
enterocolitis
Paediatric
Adult
In supine position air
collects anterior to
abdominal viscera

47. Falciform ligament sign
Normally
invisible.
Supine film, free
air rises over
anterior surface
of liver

48. Other patterns of air around liver
Doge’s Cap Sign

49. Inverted V sign
• On the supine radiograph, an inverted "V"
may be seen over the pelvis in a patient with
pneumoperitoneum.
• While in infants this is produced by the
umbilical arteries, in adults it appears to be
created by the inferior epigastric vessels

50. Continuous diaphragm sign
Sufficient
free air, left
and right
hemi-
diaphragms
appear
continous

51. Lesser sac Sign Cupola Sign
Lesser sac
sign
– (black
arrows)
The lesser sac is
positioned
posterior to the
stomach and is
usually a potential
space. There is
free connection
between the lesser
sac and the
greater sac
through the
foramen of
Winslow
Cupola
sign
– (white
arrows)
Air superior to
left lobe of
liver
Double Bubble Sign

52. Cupola Sign
The term cupola comes from a dome such as
this famous dome of the Duomo in Florence.
Air beneath the central tendon of the diaphragm

53. Triangle Sign
• The triangle sign
refers to small
triangles of free gas
that can typically be
positioned between
the large bowel and
the flank

54. Retroperitoneal Air
• Recognised by:
– Streaky, linear appearance outlining
retroperitoneal structures
– Mottled, blotchy appearance
– Relatively fixed position
• May outline:
– Psoas muscles
– Kidneys, ureters, bladder
– Aorta or IVC
– Subphrenic spaces

55. Causes of retroperitoneal air
• Bowel perforation (appendix, ileum, colon)
• Trauma (blunt or penetrating)
• Iatrogenic
• Foreign body
• Gas producing infection

56. Pneumoretroperitoneum
• This patient has free air in
the retroperitoneal space.
The air is seen surrounding
the lateral border of the right
kidney (white arrow). There
is other evidence of free gas
including Rigler's sign.
• If you are not confident that
the appearance is
pneumoretroperitoneum,
you can try an erect and
decubitus view to see if the
gas moves. If the gas is seen
to move, it's not in the
retroperitoneum.

57. Air in the bowel wall
• Signs
– Best seen in profile producing a linear lucency that
parallels the bowel
– Air en face has a mottled appearance resembling
gas mixed with faeculent material

58. Causes of air in bowel wall
• Primary Pneumatosis cystoides intestinalis (rare)
– usually affects left colon
– Produces cyst-like collections of air in the submucosa or serosa
• Secondary
– Diseases with bowel wall necrosis
– Obstructing lesions of the bowel that raise intraluminal pressure
• Complications
– Rupture into peritoneal cavity
– Dissection of air into portal venous system

59. Pneumatosis intestinalis
• Intramural air,
best
appreciated in
profile

60. Air in the biliary tree
• One or two tube-like branching lucencies in
the RUQ, conform to location of major bile
ducts

61. Causes
• “Normal” if Sphincter of Oddi incompetence
• Previous surgery including sphincterotomy or
transplantation of CBD
• Pathology (uncommon)
– Gallstone ileus: gallstone erodes through wall of
GB into the duodenum producing a fistula
between the bowel and the biliary system.
– Stone impacts in small bowel = mechanical SBO.
“ileus” misnomer

62. Biliary vs Portal Venous Air
• Portal venous air
usually associated
with bowel necrosis
• Air is peripheral
rather than central
• Numerous
branching
structures

63. Soft tissue masses
• Organomegaly
– Know normal landmarks
2 ways to identify soft tissue masses/organs:
– Direct visualisation of edges of structure
– Indirect by displacement of bowel
CT, US and MRI have essentially replaced conventional
radiography in the assessment of organomegaly and soft
tissue masses

64. Location Pattern
Abdominal Calcifications

65. First exclude artefact
Kim Kardashian’s butt – real or artefact?

66. Location
• Vascular
• Liver
• Gallbladder
• Spleen
• Pancreas
• Lymph nodes
• Adrenals
• Kidneys
• Ureters
• Bladder
• Prostate

67. Rim-like
• Calcification that has occurred in the wall of a
hollow viscus
– Cysts
• renal, splenic, hepatic
– Aneurysms
• aortic, splenic, renal artery
– Saccular organs
• Gallbladder
• Urinary bladder Calcified hydatid cysts

68. Linear/Track
• Calcification in walls of tubular structures
– Arteries
– Fallopian tubes
– Vas deferens
– Ureter
Aortoiliac calcification

69. Chinese Dragon Sign
Calcified splenic artery

70. Calcified vas deferens

71. Floccular, Amorphous, Popcorn
• Formed in solid organ or tumour
– Pancreas (chronic pancreatitis)
– Leiomyomas of uterus
– Ovarian cystadenomas
– Lymph nodes
– Adenocarcinomas of stomach, ovary, colon
– Metastases
– Soft tissue (previous trauma, crystal deposition)

72. Calcified enteric
lymph nodes
Calcified fibroids
Calcified pancreas
Floccular

73. Lamellar or laminar
• Formed around a nidus inside hollow lumen
• Concentric layers due to prolonged movement
of stone inside hollow viscus
– Renal stones
– Gallstones
– Bladder stones

74. Bladder calculi
Lamellar

75. Renal calculi
Pelvicalyceal calcifications

76. Staghorn Calcification
Renal stones are often small, but if large
can fill the renal pelvis or a calyx, taking on
its shape which is likened to a staghorn.Tubular

77. Nephrocalcinosis
Uncommonly the renal
parenchyma can become
calcified.
This is known as
nephrocalcinosis, a condition
found in disease entities such
as medullary sponge kidney
or hyperparathyroidism.
Renal calculi
Parenchymal calcification
Flocculent

78. Putty Kidney
• "Putty kidney" –
sacs of casseous,
necrotic material
(TB)
• Autonephrectomy
– small, shrunken
kidney with
dystrophic
calcification
Flocculent

79. Calcified gallstones
Lamellar

80. Conclusion
• Approach to AXR should include gas pattern,
extraluminal air, soft tissue and calcifications
• Named radiological signs are a useful way of
remembering, identifying and reporting on
films

81. References
• Herring, W. Learning Radiology 2nd
Ed, 2012
• Begg, J. Abdominal X-rays Made Easy, 1999
• http://www.wikiradiography.com
• http://www.radiopaedia.org
• http://www.imagingconsult.com
• Roche, C et al. Radiographics: Selections from the buffet of food signs in Radiology. Nov 2002, RG,
22, 1369-1384
• Young, L. Radiology Cases in Paediatric Emergency Medicine. Vol 1 Ca 2. The Target, Crescent and
Absent Liver Edge Signs.
• Raymond, B et al. Radiographics: Classic signs in uroradiology. RSN 2004
• http://www.swansea-radiology.co.uk Radiology Teaching Site. Introduction to abdominal
radiography
• Mussin, R. Postgrad Med J 2011: 87:274-287. Gas patterns on plain abdominal radiographs
• http://www.radiologymasterclass.co.uk/tutorials/abdo/abdo_x-ray_abnormalities
• Mettler: Essentials of Radiology, 2nd
Ed, 2005
• http://www.learningradiology.com/radsigns
• Muharram Food signs in radiology. International Journal of Health Sciences Vol 1 No 1. Jan 2007.

82. THANK YOU