The document provides information on imaging of intestinal obstruction. It discusses the types, causes, clinical presentations and imaging features of small bowel obstruction and large bowel obstruction. Key points include that small bowel obstruction is more common and can be caused by adhesions, hernias and tumors. Imaging findings on x-ray include dilated bowel loops and air-fluid levels. Closed loop obstruction has a characteristic "U-shaped" bowel configuration. Large bowel obstruction is usually due to cancer in adults. Common causes of neonatal bowel obstruction discussed include duodenal atresia, jejunal atresia, ileal atresia, meconium ileus and Hirschsprung's disease.

1. IMAGING OF INTESTINAL
OBSTRUCTION
Present by:
Capt. Soe Moe Htoo

2. Outline
1. Introduction
2. Types of intestinal obstruction
3. Small bowel obstruction (SBO)
4. Large bowel obstruction (LBO)
5. Imaging features of common causes of intestinal obstruction
6. Bowel obstruction mimic
7. Conclusion
2

3. INTESTINAL OBSTRUCTION
Definition:
Mechanical or functional obstruction of the intestines, preventing the
normal transit of the products of digestion
• One of the common causes of acute abdomen
• Approximately 20% of patients admitted to the hospital with an acute
abdomen have an intestinal obstruction
• May lead to high morbidity and mortality if not treated correctly
3

4. According to Obstruction Site,
• Small bowel obstruction (80 % of all mechanical intestinal obstruction)
• Large bowel obstruction (20%)
4

5. According to bowel movement,
Dynamic:
• Where peristalsis is working against a mechanical obstruction.
Adynamic:
• Mechanical element is absent
• Peristalsis my be absent(paralytic ileus)
5

6. Clinical Presentation
The four cardinal features of intestinal obstruction:
- Colicky abdominal pain
- Vomiting
- Abdominal distension
- Absolute constipation
Vary according to:
• Location of obstruction
• Duration of obstruction
• Underlying pathology
• Intestinal ischemia
6

7. Abdominal pain
- colicky in nature, around the umbilicus in SBO while in the lower
abdomen in LBO
- if it becomes continuous, think about perforation or strangulation.
- does not usually occurs in paralytic ileus
Vomiting
- starts early in SBO and late in LBO
- As obstruction progresses vomitus alters from digested food to
feculent due to enteric bacterial overgrowth
Distension
- more with lower obstruction
Constipation
-more with lower or complete obstruction
7

8. Dehydration
• More common in small bowel obstruction due to repeated vomiting
In strangulation:
• Severe constant abdominal pain
• Fever
• Tachycardia
• Tenderness with rigidity/rebound tenderness
• Shock
8

9. Goals of Imaging
• Differentiate true mechanical obstruction from ileus or constipation
• Localize the site of obstruction
• Identify an underlying cause
• Assess for complications (e.g. ischaemia or perforation)
• Assess viability of bowel segments involved
9

10. SMALL BOWEL OBSTRUCTION
Signs & Symptoms
• Intermittent, Crampy Abdominal Pain
• Nausea /Vomiting
• Abdominal distension
• Peristaltic Rushes on Auscultation
• Focal Tenderness
• Diffuse Peritonitis
SBO

11. Causes
• Congenital
• Acquired : Extrinsic, Intrinsic, Luminal
Congenital
• jejunal atresia
• ileal atresia or stenosis
• enteric duplication
• midgut volvulus
• mesenteric cyst
• Meckel diverticulum
11
SBO

12. Extrinsic Causes
1. Fibrous adhesions (75% of cases in developed countries)
2. Abdominal Hernia (75% of cases in underdeveloped countries)
3. Volvulus
4. Masses
• Extrinsic neoplasm
• Intra-abdominal abscess
• Aneurysm
• Haematoma
12
SBO

13. Intrinsic bowel wall causes
1. Inflammation (e.g. Crohn, TB, Eosinophilic gastritis)
2. Tumour (Primary small bowel neoplasm are rare, <2% of all GI
malignancy)
3. Radiation enteritis (usually >1yr after therapy)
4. Intestinal ischaemia
5. Intramural haematoma (Traumatic, iatrogenic)
6. Intussusception
13
SBO

14. Intraluminal causes
• Swallowed, e.g. foreign body, bezoar
• Gallstone ileus
• rare complication of recurrent cholecystitis
• biliary-intestinal fistula with impaction of a gallstone in the small
bowel
• Meconium ileus
• Worm infestation
14
SBO

15. Radiological Features
Erect AXR
• This is not routinely performed
• >2 fluid levels within dilated (> 2.5cm) small bowel loops
Supine AXR
• Dilated loops of small bowel proximal to the obstruction
• Collapsed colon
• Cause may be identified (e.g. an inguinal hernia may appear as a gas-
filled viscus below the level of the inguinal ligament)
15
SBO

16. Obstruction (high-grade mechanical obstruction) may also present with
the following features:
• Gasless abdomen
• ‘String of beads’ sign: a line of gas bubbles trapped between the
valvulae conniventes within almost completely fluid-filled and very
dilated small bowel
16
SBO

17. 17
String of beads
SBO

18. 18
SBO

19. US
Findings suggestive of small bowel obstruction
• dilated bowel loop (diameter >2.5 cm)
• decreased bowel peristalsis
Findings suggestive of bowel ischaemia/infarction
• fluid-filled distended bowel with extraluminal free fluid between
bowel loops
• no peristalsis
• bowel wall thickening >3 mm
19
SBO

20. CT
• Cause may be identified
• Adhesions are suggested by angulated and tethering of the bowel
loops
• Transition point (where bowel calibre changes from normal to
abnormal)
• Dilated small bowel loops >2.5-3 cm from outer wall to outer wall
• Collapsed or normal calibre bowel distal to the transitional point
• Bowel wall thickening
• Surrounding mesenteric fat stranding indicating inflammation
• Twisting of the mesentery in cases of volvulus
20
SBO

21. According to Configuration,
• Simple obstruction: a transition zone may be seen with dilated small
bowel loops proximal to the obstruction, and collapsed loops distally
• Closed-loop obstruction: a U- or V-shaped configuration of the
dilated loops with a fixed radial distribution
• Strangulated bowel: this represents incarceration of the two limbs of
the mechanical small bowel obstruction with subsequent ischaemia
21

22. 22

23. Closed loop obstruction
• Specific type of small bowel obstruction
• secondary to adhesions, a twist of the mesentery or herniation.
• Two points of a bowel are obstructed at a single location thus forming
a closed loop
• Closed loop usually rotates around its axis, forming a small intestinal
volvulus.
23

24. 24

25. CT
Some or all of the following signs may be demonstrated on CT:
• marked distension of a segment of small bowel
• radially distributed, C or U-shaped small bowel loops
• “Beak sign": of the tapering bowel loops at the point of obstruction
• “Whirl sign": of the tightly twisted mesentery
• two adjacent collapsed loops of bowel
• if strangulation is present, signs of bowel ischaemia (pneumatosis
intestinalis, pneumatosis portalis, pneumoperitoneum)
• “Small bowel feces" sign, with feculent matter mixed with gas bubbles
seen within a dilated segment of small bowel. This results from stasis
and it is present in about 82% of SBOs.
25

26. 26
'U' or 'C' shaped loops of bowel.
Point of obstruction has a beak-like appearance

27. Closed loop obstruction with radial array of dilated loops.
There is bowel wall thickening and mesenteric edema indicating ischemia
27

28. 28
Whirl sign: of the tightly twisted mesentery

29. 29

30. 30

31. LARGE BOWEL OBSTRUCTION
• Less common than small bowel obstructions, 20% of all bowel
obstructions
• Underlying aetiology of large bowel obstructions is age-dependant,
• In adulthood, the most common cause is colonic cancer (50-60%)
31

32. 32

33. Duodenal Atresia
• 1 in 5,000-10,000 newborns
• No gender predilection
• One of the commonest causes of complete fetal bowel obstruction
• Proximal duodenal atresia – d/t failed bowel lumen recanalization in
early fetal life (late first trimester)
• Distal atresia – d/t secondary of ischemic episode
• 50% have history of polyhydramnios
33

34. Imaging features:
• Double-bubble appearance - gas-filled distended stomach and
proximal duodenum (Non-specific)
• Dilatation of the duodenum is a sign of chronic obstruction
• Seen in duodenal atresia, duodenal web and annular pancreas
• In midgut volvulus, obstruction occurs acutely after birth, the
duodenum is not usually dilated
34
Duodenal Atresia

35. 35

36. Differential diagnosis of duodenal obstruction:
• Malrotation with Ladd bands and midgut volvulus - can be partial or
complete obstruction.
• Duodenal web - partial obstruction with small amount of distal bowel
gas
• Annular pancreas.
• Preduodenal portal vein
36
Duodenal Atresia

37. 37

38. 38

39. Duodenal atresia
AXR of a newborn with bilious vomiting and abnormal antenatal ultrasound
showing polyhydramnios and dilated stomach
39
Duodenal Atresia

40. Duodenal Web
• Variant of duodenal stenosis
• Caused by a duodenal membrane
• In partial duodenal obstruction, upper GI contrast studies help to
distinguish between duodenal web and malrotation with Ladd bands
or midgut volvulus.
40

41. Imaging features:
• Plain radiograph: dilated gas filled stomach and duodenum 'double
bubble’ with small amount of distal bowel gas.
• 'Windsock' or 'dimple' appearance on upper GI contrast: representing
the web.
41
Duodenal Web

42. Duodenal web
AXR of a newborn with bilious vomiting.
42
Duodenal Web

43. Jejunal Atresia
• More common than duodenal atresia
• Incidence 1 in 1,000 live births
• Arise form an ischemic event in utero and not infrequently involves
more than one segment (50%) of jejunum
43

44. Imaging Findings:
• Triple-bubble sign
 Double bubble sign + Third bubble (air filled dilated jejunum)
• No gas in the distal bowel
Differential Diagnosis of proximal obstruction:
Malrotation with midgut Volvulus
• Plain film confirms complete obstruction if there is no distal gas
• If there is small amount of distal gas  upper GI study (to distinguish
from malrotation/ volvulus)
44
Jejunal Atresia

45. • Several dilated proximal bowel loops in the
upper abdomen
• No distal bowel gas indicating complete
high obstruction due to Jejunal atresia
• Small amount of intra-abdominal
calcification (arrow) represents meconium
peritonitis due to in-utero perforation
secondary to the bowel obstruction
Newborn with abnormal antenatal ultrasound
suggesting bowel obstruction
45
Jejunal Atresia

46. Ileal atresia
• In-utero ischemic event resulting in single or multiple atresias
• Can associated with mesenteric defects
• Usually presents within first few days after birth
• Abdominal distension, bilious vomiting and failure to pass meconium
• May be diagnosed on antenatal ultrasound (with polyhydramios and
signs of bowel obstruction)
46

47. Imaging Findings:
• Numerous dilated bowel loops (indicating a low obstruction)
• Multiple air-fluid levels
• Calcifications (indicating meconium peritonitis in in-utero perforation)
• Microcolon and blind ending ileum on contrast enema
47
Ileal atresia

48. Differential Diagnosis of distal bowel obstruction:
• Meconium ileus
• Meconium plug and small left colon syndrome
• Total colonic Hirschsprung disease
• Colonic atresia
48
Ileal atresia

49. Ileal atresia
7(a) Multiple dilated bowel loops indicating a distal obstruction
7(b) Contrast enema show a microcolon with a blind ending small distal ileum
representing ileal atresia.
AXR of a newborn with abdominal distension and feeding intolerance.
49
Ileal atresia

50. 50

51. Ileal atresia
(a) Multiple air-fluid levels occupying the entire abdominal cavity.
(b) Barium enema: numerous dilated, air-filled loops of bowel and a
small, unused colon (functional microcolon).
51
Ileal atresia

52. Colonic atresia
(a) Radiograph shows distended loops of bowel similar to those seen in low small bowel
obstruction.
(b) Barium enema: microcolon with complete obstruction to the retrograde flow of
barium in the transverse portion of the colon.
52

53. Volvulus
• Volvulus = Twisting of intestine upon itself
• Sigmoid volvulus is three to four times more common than cecal
volvulus
53

54. 54

55. 55

56. 56

57. 57

58. 58
Sigmoid Volvulus

59. Meconium ileus
• Newborn bowel obstruction
• Secondary to thick tenacious meconium impacted in distal ileum
• Accounts for 20% of neonatal intestinal obstruction
• 50% of cases are complicated with perforation
• Usually managed conservatively with gastrograffin enema washout in
uncomplicated intestinal obstruction
59

60. Associations:
• Cystic fibrosis (almost all patients with meconium ileus have cystic
fibrosis and 15% of CF patients present with meconium ileus)
• Pancreatic duct stenosis/atresia
• Pancreatic insufficiency
60
Meconium ileus

61. Imaging features:
• 'Bubbly'/frothy appearance of intestinal contents (seen in the right
lower quadrant in 50-66%).
Contrast enema:
• Distal small bowel impacted with filling defects (meconium pellets)
• Microcolon
61
Meconium ileus

62. Meconium ileus
(a) Abdominal radiograph of a neonate who failed to pass meconium, showing distended gas filled bowel
loops and "soap bubble" appearance in the right lower abdomen representing the impacted
meconium in the distal ileum (arrow).
(b) Contrast enema examination demonstrates small-caliber colon "microcolon". Numerous filling defects
in the distal ileum represent the impacted meconium pellets. Note the multiple proximal dilated loops
of bowel.
62
Meconium ileus

63. Meconium ileus
(a) Abdominal scout radiograph shows marked distention of the small bowel and a
“soap bubble” appearance in the right side of the abdomen (arrows), a finding
suggestive of mottled air and feces.
(b) US image shows dilated, fluid-filled intestinal loops containing echogenic material
(calcified meconium) (arrows). Associated ileal atresia was seen at surgery. 63
Meconium ileus

64. Hirschsprung disease
• Most common cause of lower intestinal obstruction in neonates
• 1 in 5000 live births
• Male predominance (80%)
• Always begins in internal anal sphincter
• Extends proximally for a variable length of gut
64

65. Pathogenesis
65
Migratory failure of neural crest cells
Functional obstruction
Spasm of the affected segment of colon
Congenital absence of colonic ganglion
cells

66. Pathogenesis
66
Hirschsprung

67. Types of Hirschsprung disease:
1. Short segment disease (rectum and sigmoid) - 80%
2. Long segment disease (Rectum and sigmoid with the transition zone
above the rectosigmoid) - 15-25%
3. Total colonic Hirschsprung (entire colon) - <5 %
4. Total intestinal disease - very rare
5. Ultrashort segment (only ano-rectal junction) – very rare
6. Presence of skip lesions in Hirschsprung’s disease is extremely rare
67
Hirschsprung

68. Associations:
• Genitourinary anomalies (11%)
• Congenital cardiac disease (6%)
• Trisomy 21 (5%)
68
Hirschsprung

69. Clinical presentation
• Failure to pass meconium in 1st 24 hr. of life
• Abdominal distension, bilious vomiting, refusal to feed
Older children present late with
• Long standing history of constipation since birth
• Toxic Megacolon (Fever, abdominal distension, bilious vomiting,
explosive diarrhea, dehydration, shock)
• Spontaneous perforation (esp. in long segment)
69
Hirschsprung

70. • Definitive diagnosis - by full thickness rectal biopsy
• Contrast enema - usually demonstrates the transition zone
(but can be normal in ultrashort segment disease)
70
Hirschsprung

71. Imaging features:
• AXR: Multiple dilated bowel loops with lack of gas in the rectum
71
Hirschsprung

72. Barium enema
• Contrast agent should be prepared with normal saline
• Performed by inserting a straight tipped catheter just beyond the anal
sphincter
• Patient placed in lateral position
• Should infused barium slowly
• Rapid infusion can distend and mask the transition zone
• Diagnostic feature in short segment disease is funnel shaped
transition zone and reversal of the recto-sigmoid ratio.
72
Hirschsprung

73. Rectosigmoid ratio
• Measurement of the diameter of the rectum divided by sigmoid colon
during contrast enema.
• Use in the diagnosis of Hirschsprung disease
• Normal children have a rectum that is larger than the sigmoid (i.e.
rectosigmoid ratio >1).
• A rectosigmoid ratio (R/S) less than 1 suggests the diagnosis of short-
segment Hirschsprung disease
73

74. 74

75. • Transition zone between the narrowed affected distal colon and the
dilated innervated proximal colon.
• Short segment: Rectum smaller than the sigmoid. Rectum in an
inverted cone shape.
• Long segment: Transition zone is above the recto-sigmoid junction.
• Total colonic Hirschsprung: Microcolon
• Normal rectum in 33%
• “Saw- tooth” appearance due to irregular spasm of the affected
segment
• Enterocolitis: thickened and ulcerated bowel wall
• 24 hr delayed films – Poor barium emptying through the colon
75
Hirschsprung

76. 76

77. Differential diagnosis of distal bowel obstruction:
• Meconium ileus
• Meconium plug and small left colon
• Ileal atresia
• Colonic atresia
77
Hirschsprung

78. Hirschsprung disease
(a) AXR of a newborn who failed to pass meconium, demonstrates multiple dilated loops of
bowel consistent with distal obstruction.
(b)(c) Lateral and AP views of contrast enema examination of the same neonate illustrating a
narrowed rectum compared to the sigmoid.
The rectum shows irregular contractions.
This is the classic 'inverted cone shape' rectum and 'saw-tooth’ appearance.
Rectal biopsy confirmed short segment Hirschsprung disease. 78
Hirschsprung

79. Hirschsprung disease.
9(d) Dilated transverse colon with the transition zone at the splenic flexure (arrow head)
corresponding to the lateral and AP barium enema contrast images
(e) and (f) (curved arrow). The descending and sigmoid colon is narrowed with spasm and the rectum
has a "saw-tooth appearance" due to abnormally contractions (black arrow).
Biopsy confirmed long segment Hirschsprung disease. 79

80. Hirschsprung disease in a 6-month-old infant with a history of chronic
constipation.
Frontal (a) and lateral (b) images from a barium enema study show the proximal
sigmoid colon and descending colon as greatly dilated compared with the distal
colon and rectum. 80
Hirschsprung

81. Intussusception
• Invagination of one segment of bowel into another, leading to edema
and venous congestion within the bowel wall.
• Most common type - Ileocolic
• Majority - under 1 year of age, with a peak incidence between 5 and 9
months
• M:F (3:2)
81

82. 82
Intussusception

83. LEAD POINT
• A lead point is a lesion or variation in the intestine that is trapped by
peristalsis and dragged into a distal segment of the intestine, causing
intussusception.
• Meckel diverticulum
• Polyp
• Tumor
• Hematoma
• Vascular malformation
83
Intussusception

84. Intussusceptum (white arrow) and Intussuscipiens (black arrow)
84
Intussusception

85. Etiology
85
Intussusception

86. Etiology (Cont.)
Idiopathic
• Approximately 75 % of cases are idiopathic
• No clear disease trigger or pathological lead point
Influence of viral factors
• Has a seasonal variation, with peaks coinciding with seasonal viral
gastroenteritis.
• 30 % experience viral illness (URTI, otitis media, flu-like symptoms)
before the onset of intussusception.
86
Intussusception

87. 87
Viral infections
Stimulate lymphatic tissue in the intestinal
tract
Hypertrophy of Peyer patches in the
lymphoid-rich terminal ileum
Act as a lead point for ileocolic
intussusception

88. Presentation
• The classic triad of symptoms:
(1) intermittent colicky abdominal pain (about every 10-20 min)
(2) vomiting (rapidly becoming bile-stained)
(3) 'redcurrant jelly' stool
• Neurological symptoms (lethargy, hypotonia or sudden alterations of
consciousness)
88
Intussusception

89. Pathological process of intussusception
89
Intussusception

90. Imaging features:
Plain X-ray(Abd)
• Plain radiograph is normal in 25%.
• Small tissue mass and crescent of air around the intussuceptum in the
right abdomen.
• Small bowel obstruction
• Paucity of bowel gas distally
• Meniscus sign: Crescent of gas within colonic lumen that outlines the
apex of intussusceptum
90
Intussusception

91. 91
Intussusception

92. Meniscus sign
92
Intussusception

93. 93
Intussusception

94. Contrast Enema
1. Coil spring appearance:
- Trapping of barium between the edematous mucosal folds of
the returning limb of intussusceptum & wall of intussuscepian.
2. Meniscus sign:
- Convex intraluminal mass
NOTE: Barium enema is contraindicated in perforation.
94
Intussusception

95. COIL SPRING SIGN
95
Intussusception

96. Barium enema showed filling defect with crab's
claw sign at the mid transverse colon
96
Intussusception

97. Ultrasound
• Up to 100% accuracy for the diagnosis of intussusception
• portable, noninvasive, and without radiation
• Characteristic finding>>>>3- to 5-cm diameter mass, typical target or
doughnut sign found just deep to the anterior abdominal wall on the
right side can detect a possible pathologic lead point with higher
frequency (66%) than contrast (40%) or air enema (11%)
• “Target” appearance multiple concentric rings and central mesenteric
fat in the transverse plane.
• “Pseudo-kidney“ appearance: On longitudinal images,
intussusception often shows peripheral hypoechoic bowel with
central increased echoes.
97
Intussusception

98. Warning signs of necrosis on US
• absence of blood flow on Doppler a thick peripheral hypoechoic rim
• free intraperitoneal fluid
• fluid trapped within the intussusceptum,
• enlarged lymph nodes dragged with the mesentery into the
intussusception
98
Intussusception

99. • Measurement of intussusception assist in differentiating between
ileocolic and small bowel-small bowel intussusception
• Small bowel-small bowel intussusception is smaller, typically self-
limiting, and does not require intervention.
• Ultrasound findings such as intussuscepted lymph nodes and
interloop fluid indicate increased difficulty in an attempt at reduction
99
Intussusception

100. Target sign
100

101. • In ileocolic type, the patient should undergo reduction via air or
contrast enema to prevent complications (bowel wall ischemia or
necrosis, perforation, and shock)
• Surgery for patients in whom reduction is unsuccessful or have
contraindications to fluoroscopic reduction (e.g. free air, peritonitis,
or signs of shock).
101
Intussusception

102. Non-surgical Reduction
• Pneumatic or hydrostatic reduction may be performed
• In both procedures, an enema tube is placed in the patient’s rectum
• In pneumatic reduction, air is pumped manually through the tube
into the colon, pushing the intussusceptum through the ileocecal
valve.
• A pressure of 120 mm Hg or less should be maintained
• If the patient engages in a Valsalva maneuver, the pressure may
intermittently increase
• When the mass is no longer seen and air enters the distal small
bowel, the reduction is considered successful.
• At the end of the procedure, post reduction image must be taken.
(to check +/-pneumoperitoneum)
102
Intussusception

103. • In hydrostatic reduction, water-soluble isotonic or LOCM is hung 3
feet above the table and allowed to flow freely into the colon.
• When the intussusceptum reduces, contrast is seen in distal small
bowel loops.
• Advantages of the pneumatic technique:
• Faster reduction
• Decreased radiation, and
• Air rather than contrast entering the peritoneal cavity (in cases of perforation)
103
Intussusception

104. Intussusception
Distal SBO with a soft tissue mass in the right lower
quadrant representing an ileocolic intussusception.
Note the absence of gas in the colon and rectum.
104
Intussusception

105. Intussusception on ultrasound
(A) Transverse and (B) longitudinal gray-scale US images
- characteristic of intussusception with a target and “pseudokidney”
appearance, respectively.
- Lymph nodes can be seen with the intussusceptum on the
transverse image (arrow) 105
Intussusception

106. CT and MRI
• Are not routinely used
• Intussusception found incidentally on imaging performed for
another suspected diagnosis
• target or doughnut sign
106
Intussusception

107. Diverticulitis
• Less common (10% of LBO)
• Due to bowel wall edema and pericolonic inflammation
• Chronic diverticulitis can produce both LBO and a chronically
dilated colon.
• Most common location for obstructing diverticulitis  Sigmoid colon
107

108. CT
• Segmental, symmetric bowel wall thickening with hyperemia, which is
typically in a longer segment than malignant lesions (> 10 cm)
108

109. 109
Images in a 47-year-old man with LBO caused by diverticulitis.
(a) CT scout image shows air-filled dilated colon terminating in the left pelvis (arrow)
(b) Axial CT image of the pelvis after the administration of intravenous contrast material shows dilated,
stool-filled large bowel extending into the pelvis where the sigmoid colon is thick walled and inflamed
(white arrow). There is fluid in the root of the mesentery (black arrow).

110. Acute Colonic Pseudo-Obstruction (ACPO)
(Ogilvie’s Syndrome)
• Pseudo obstruction secondary to interruption of sympathetic
innervation of the colon
• Most common in male over 60 years
• Abdominal tenderness, a common sign in the setting of LBO, is not a
prominent feature of ACPO
110

111. 111

112. AXR
• Marked colonic distension predominantly cecum, ascending colon,
and transverse colon.
• Gas may also extend to the sigmoid colon and rectum.
• In patients with ACPO, repositioning the patient after an initial supine
radiograph  obtaining Rt. lateral decubitus after a few minutes 
usually results air filling the distal colon.
• Prior abdominal radiographs and a history of chronically dilated large
bowel
CT
• Large bowel dilatation with the absence of a transition point
112

113. Obtained after cardiac surgery in a 55-year-old man with
abdominal distension.
(a) Radiograph shows marked distension of the entire colon
despite rectal tube (arrow) in place.
(b) Radiograph after administration of water-soluble enema
demonstrates patent colon without evidence of
obstruction. The pseudo-obstruction resolved with
colonic decompression tube placement.
113

114. 114

115. Bowel Perforation
• Can be from obstruction secondary to atresia, meconium ileus and
necotizing enterocolitis.
• Free air collects in the non-dependent portion of the abdomen
• Can seen on the supine abdominal radiograph as lucency over the
central abdomen, over the liver and outlining the falciform ligament.
• Lateral decubitus projection can be helpful in difficult cases, as the
free air will rise to the non-dependent areas.
115

116. Pneumoperitoneum.
(a) Lateral decubitus radiograph demonstrating the free air rising to the non
dependent area above the liver (curved arrow).
(b) Chest radiograph of a neonate showing the falciform ligament (arrow)
outlined by free air and therefore becomes visible
116

117. 117

118. TAKE HOME MESSAGE
118

119. Tips for AXR
• Jejunum is characterized by valvulae conniventes(completely pass
across the width & regularly placed)
• Ileum is featureless.
• Caecum is shown by rounded gas shadow in RIF.
• Colon shows haustral folds.
• Fluid level appears later than gas shadow
• Two fluid level in small bowel considered normal.
• No. of fluid level is proportional to degree of obstruction

120. Goals of Imaging
• Differentiate true mechanical obstruction from ileus or constipation
• Localize the site of obstruction
• Identify an underlying cause
• Assess for complications (e.g. ischaemia or perforation)
• Assess viability of bowel segments involved
120

121. 121

122. THANK YOU
122