The document discusses the concept of 'acute abdomen', which includes a variety of medical conditions requiring urgent evaluation and treatment. It outlines the different imaging modalities used in diagnosing acute abdominal conditions, such as plain X-rays, ultrasound, CT, and MRI, while detailing their appropriate applications based on clinical suspicion. Additionally, it highlights specific conditions and signs related to intestinal obstructions, emphasizing the importance of various diagnostic imaging techniques in determining the cause and severity of abdominal emergencies.

1. Dr.koushik sharma
ACUTE ABDOMEN

2.  “Acute abdomen” is a term used to encompass a
spectrum of surgical, medical and gynecological
conditions (intra-abdominal process), ranging from
the trivial to the life threatening, which require
hospital admission, investigation and treatment

4. Generalized AP
 Perforation
 AAA
 Acute pancreatitis
 Bilateral pleurisy

5. Central AP
 Early appendicitis
 SBO
 Acute gastritis
 Acute pancreatitis
 Ruptured AAA
 Mesenteric thrombosis

6. Epigastric pain
 DU / GU
 Oesophagitis
 Acute pancreatitis
 AAA

7. RUQ pain
 Gallbladder disease
 DU
 Acute pancreatitis
 Pneumonia
 Subphrenic abscess

8. LUQ pain
 GU
 Pneumonia
 Acute pancreatitis
 Spontaneous splenic
rupture
 Acute perinephritis
 Subphrenic abscess

9. Suprapubic pain
 Acute urinary retention
 UTIs
 Cystitis
 PID
 Ectopic pregnancy
 Diverticulitis

10. RIF pain
 Acute appendicitis
 Mesenteric adenitis (young)
 Diverticulitis
 PID
 Salpingitis
 Ureteric colic
 Meckel’s diverticulum
 Ectopic pregnancy
 Crohn’s disease
 Biliary colic (low-lying gall
bladder)

11. Loin pain
 Muscle strain
 UTIs
 Renal stones
 Pyelonephritis

12. LIF pain
 Diverticulitis
 Constipation
 IBS
 PID
 Rectal Ca
 UC
 Ectopic pregnancy

13.  The various imaging modalities available for
investigating the acute abdomen include:
 plain films,
 contrast studies
 ultrasound (US)
 computed tomography(CT), and
 magnetic resonance imaging (MRI).
 The choice of the initial modality to be used should
be guided by the disease suspected on clinical
grounds

14. Plain radiography
 plain radiographs continue to be initial imaging
modality
 In intestinal obstruction and perforation.
 Contrast examinations have a limited role. An
upper GI series with water soluble contrast may
be performed in cases of suspected perforation or
a contrast enema may be required to confirm a
colonic obstruction.

15. Ultrasound
US is the ideal screening modality for suspected
 hepatobiliary disease
 suspected pelvic pathology
such as ectopic gestation or acute pelvic inflammatory
disease (PID).
 right lower quadrant pain.
 In cases of suspected intestinal obstruction,
to differentiate between
mechanical obstruction and paralytic ileus. US demonstrates
increased peristalsis in cases of mechanical obstruction, whereas
presence of dilated, atonic loops suggest the diagnosis of
paralytic ILEUS.
 US is also helpful in localizing intra-abdominal abscesses,
particularly in the solid viscera.

16. CT
 MDCT has become the imaging modality of
 choice for evaluation of the acute abdomen. It
provides
 a comprehensive view of all the intra-abdominal solid
 and hollow viscera, as well as the peritoneum,
mesentery,
 lymph nodes and retroperitoneum. Data can be
acquired
 in different phases making MDCT an ideal modality
for
 evaluation of suspected mesenteric ischemia
 or vasculardisorders such as abdominal aortic
aneurysms.
 Low dose unenhanced CT has replaced excretory

17. MRI
Recent improvements in resolution and
development of faster breath-hold sequences
have drastically increased the utility of MRI in
evaluation of the gut.
However, MRI is still not routinely used for
evaluation of an acute abdomen except in
situations where iodinated contrast cannot be
administered or in pregnant patients.

18. What to Examine by
Plain X-ray
 Gas pattern
 Extraluminal air
 Soft tissue masses
 Calcifications
 Skeletal pathology

19. Normal Gas Pattern
 Stomach
 Always
 Small Bowel
 Two or three loops of non-distended bowel
 Normal diameter = 2.5 cm
 Large Bowel
 In rectum or sigmoid – almost always

20. Gas in stomach
Gas in a few
loops of small
bowel
Gas in
rectum or
sigmoid
Normal Gas Pattern

21. Normal Fluid Levels
 Stomach
 Always (except supine film)
 Small Bowel
 Two or three levels possible
 Large Bowel
 None normally

22. Erect Abdomen
Always air/fluid
level in
stomach
A few air/fluid
levels in
small bowel

23. Large vs. Small Bowel
 Large Bowel
 Peripheral
 Haustral markings don't extend
from wall to wall
 Small Bowel
 Central
 Valvulae extend across lumen

24. Haustra films Faecal mottling

25. Complete Abdomen
Obstruction Series
 Supine
 Erect or left decubitus
 Chest - erect or supine
 Prone or lateral rectum

26. Complete Abdomen
Supine
 Looking for
 Scout film for gas
pattern
 Calcifications
 Soft tissue masses
 Substitute – none

27. Complete Abdomen
Erect
 Looking for
 Free air
 Air-fluid levels
 Substitute – left lateral
decubitus

28. Complete Abdomen
Erect Chest
 Looking for
 Free air
 Pneumonia at bases
 Pleural effusions
 Substitute – supine chest

29. Complete Abdomen
Prone
 Looking for
 Gas in rectum/sigmoid
 Gas in ascending and
descending colon
 Substitute – lateral rectum

30. Abnormal Gas Patterns
1. Functional Ileus
 Localized (Sentinel Loops)
 Generalized adynamic ileus
2. Mechanical Obstruction
 SBO
 LBO

31. Sentinel Loops
Supine Prone
Localized Ileus Key Features
 One or two persistently dilated loops of large
or small bowel
 Gas in rectum or sigmoid

32. Pancreatitis
Ulcer
Diverticulitis
Cholecystitis
Appendicitis
Sentinel Loops
Localized Ileus

33. Localized Ileus
Pitfalls
 May resemble early
mechanical SBO
 Clinical course
 Get follow-up

34. Generalized Ileus
Key Features
 Gas in dilated small bowel and large bowel to rectum
 Long air-fluid levels
 post-op patients have generalized ileus
 Other causes:-
 Peritonitis
 Hypokalemia
 Metabolic disorder as hypothyroidism
 Vascular occlusion

35. Generalized Adynamic Ileus
Supine Erect

36. The distinction between small &
large-bowel dilatation
Small bowel large bowel
1. vulvulae conniventes present in jejunum absent
2. number of loops many few
3. distribution of loops central peripheral
4. haustra absent present
5. diameter 3-5 cm 5 cm +
6. radius of curvature small large
7. solid feces absent *present
haustra may be completely absent from the descending & sigmoid colon.

37. Abnormal Gas Patterns
Ileus and Obstruction
 Localized ileus
 Generalized ileus
 Mechanical SBO
 Mechanical LBO

38. Conditions causing extraluminal
air
 Perforated abdominal viscus
 Abscesses (subphrenic and other)
 Biliary fistula
 Cholangitis
 Pneumatosis coli
 Necrotising enterocolitis
 Portal pyaemia

39. Extraluminal Air
Free Intraperitoneal Air

40. Chest X-ray
This is an essential examination in any patient with
acute abdomen because:
1-It is the best radiograph to show the presence of a small
pneumoperitoneum. (even 2ml)
2-A number of chest conditions may present as an acute
abdominal pain : pneumonia (particularly lower lobe), MI,
… .
3- Acute abdominal conditions may be complicated by chest
pathology: pleural effusion frequently complicate acute
pancreatitis.
4-Even when the chest radiograph is normal it
acts as a valuable baseline.

41. Small
amount

42. Signs in pneumoperitoneum
42
Erect chest radiograph reveals free gas between the liver and both does of
diaphragm.

43. 43
Left lateral decubitus film showing gas between the liver and abdominal wall.

44. gns of pneumoperitoneum of supine radiograph
44
 Right upper quadrant gas
Peri hepatic
Sub hepatic
Morrison’s pouch
 Fissure for ligament teres
 Rigler’s (double wall sign)
 Ligament visualization
Falciform
Umbilical inverted ‘V’ sign
 Triangular air
 The cupola sign
 Football or air dome
 Scrotal air in children

45. Crescent sign
Free Intraperitoneal Air

46. Gas in subhepatic space
46
Supine abdominal radiograph shows an elliptical collection of air within the
subhepatic space

47. Falciform ligament sign

48. Doges cap sign
48
 Doges Cap sign refers to
free air in Morrison's
pouch.
 Morrison's pouch is
normally a potential space
between the right kidney
and the liver

49. Triangular gas shadow superior to kidney and postero-inferior to 11th rib
49

50. Rigler’s sign
50
Rigler's sign refers to the appearance of the bowel wall on
plain film when it is outlined by intraluminal and extraluminal
air .The extra luminal air is free peritoneal gas

51. Falciform ligament visualization
51
Visualization of Falciform ligament by free gas on either side of
the ligament

52. Football sign
52
 The football sign likens the massively air-filled
peritoneum to an American football
 In the supine position, free air collects anterior
to the abdominal viscera, producing a sharp
interface with the parietal peritoneum and
thereby creating the football outline

53. 53

54. Double Bubble Sign
54
Two collections of overlapping gas- one of these collections is sub diaphragmatic free
gas and the other is normal gas within the fundus of the stomach

55. The Cupola Sign
55
An arcuate collection of free intraperitoneal air beneath the central tendon of
diaphragm. The superior border is well defined (arrows) compared with the inferior
extent of the collection.

56. The Triangle Sign
56
The triangle sign refers to small triangles of free gas that can typically be positioned
between the large bowel and the flank(black arrow)

57. CONDITIONS SIMULATING PNEUMOPERITONEUM
57
1. Chilaiditi’s syndrome-intestine between liver and
diaphragm
2. Subphrenic abscess
3. Curvilinear supradiaphragmatic pulmonary
collapse
4. Subdiaphragmatic fat
5. Cyst in pneumatosis intestinalis
6. Sub pulmonary pneumothorax

58. Chilaiditi’s syndrome
Chilaiditi’s syndrome is an
important normal variant on the
erect chest radiograph,
which must be distinguished from
pathological free gas under the
diaphragm. (apparent, as
haustra are seen within the gas
filled structure). This gas is still
contained in the bowel loop.

59. 59
Chilaiditi’s syndrome-
intestine between liver
and diaphragm

60. CONDITIONS SIMULATING PNEUMOPERITONEUM
60
Right sided subphrenic
abscess

61. CONDITIONS SIMULATING PNEUMOPERITONEUM
61
Large bulla at the base of the
right lung mimics a large
pneumoperitoneum

62. Intestinal obstruction:

63. Intestinal obstruction:
 Gastric dilatation : could be
 Part of paralytic ileus
(functional).
 Mechanical : usually
caused by peptic ulceration
or a carcinoma of the
pyloric antrum , often lead
to massive fluid filled
stomach which occupy
most of the upper
abdomen.

64. GASTRIC DILATATION
Causes
1. Mechanical gastric outlet
obstruction.
2. Paralytic ileus
3. Gastric volvulus
4. Air swallowing.
64

65. GASTRIC VOLVULUS
65
o Twisting of the stomach around its longitudinal or
mesenteric axis
o Organoaxial volvulus - Stomach rotates along its
long axis and becomes obstructed, with the
greater curvature being displaced superiorly and
the lesser curvature located more caudally in the
abdomen

67. 67
 Mesenteroaxial volvulus --less common , occurs when the
stomach rotates along its short axis, with resultant
displacement of the antrum above the gastroesophageal
junction

69. Mechanical SBO
Key Features
 Dilated small bowel
 Little gas in colon, especially
rectum
 Key: disproportionate
dilatation of SB
SBO

70. Mechanical SBO
Causes
 Adhesions
 Hernia*
 Volvulus
 Gallstone ileus*
 Intussusception
*Cause may be visible on plain film

71. Mechanical SBO
Pitfalls
 Early SBO may
resemble localized ileus
-get F/O

72. Differentiating SBO from Paralytic Ileus
SBO Ileus
Etiology
Patient with prior
surgery weeks to years
prior
Recent (hours) post-
operative patient
Pain Colicky Not a prominent feature
Abdominal
distension
Frequently prominent May not be apparent
Bowel sounds Usually increased Usually absent
Small bowel
dilatation
Present Present
Large bowel
dilatation
Absent Present
72

73. Mechanical LBO
Key Features
 Dilated colon to point of obstruction
 Little or no air in rectum/sigmoid
 Little or no gas in small bowel, if…
 Ileocecal valve remains competent

74. LBO

75. LBO
Supine
Prone

76. Mechanical LBO
Causes
 Tumor
 Volvulus
 Hernia
 Diverticulitis
 Intussusception

78. Mechanical LBO
Pitfalls
 Incompetent ileocecal valve
 Large bowel decompresses into small bowel
 May look like SBO
 Get BE or follow-up

79. Carcinoma of Sigmoid – LBO –
Decompressed into SB
ProneSupine

81. The goals of imaging in a patient with suspected intestinal
obstruction have been defined and are as follows:
1. To confirm that it is a true obstruction and to
differentiate it from an ileus.
2. To determine the level of obstruction.
3. To determine the cause of the obstruction.
4. To look for findings of strangulation.
5. To allow a good management either medically or
surgically by laparoscopy or laparoscopy).

82. Post-op C-section Adynamic
Ileus

83. Mesenteric Occlusion

84. Small bowel obstruction
 Small bowel obstruction (SBO) accounts for approximately
4% of all patients presenting with an acute abdomen.
 The commonest cause is adhesions due to previous
surgery .
 The main value of plain film is in assessing the degree
& severity of the obstruction (not the cause).
 On plain film, changes in small bowel obstruction may
appear after 3-5 hours if there is complete obstruction
and marked after 12 hours.
 Radiologically, complete obstruction of the small
bowel usually causes small bowel dilatation with
accumulation of both gas & fluid and a reduction in
caliber of the large bowel, if dilated gas filled loops of
small bowel will be readily identified on the supine

85. Small Bowel Obstruction
 The 'Small Bowel Feces Sign' (SBFS) is a very
useful sign as it is seen at the zone of transition
thus facilitating identification of the cause of the
obstruction.
 The SBFS has been defined as gas and
particulate material within a dilated small-bowel
loop that simulates the appearance of feces.

86. if fluid filled loops
 The dilated small bowel loops
appears as a sausage, oval or
round soft tissue densities that
change in position in different
views, sometime with small
gas bubbles trapped in rows
between the vulvulae
conniventes on horizontal ray
films; this is known as 'string
of beads' sign which is
virtually diagnostic of small
bowel obstruction and does
not occur in normal people.

87.  Strangulating obstruction is a mechanical
obstruction caused when two limbs of a loop are
incarcerated within a hernia so as to cause
vascular compromise by compression of the
mesenteric vessels.
 Presence of thumb-printing due to submucosal
edema or hemorrhage should suggest ischemia
in the loops. If left untreated, the ischemia may
progress causing breach of the mucosa,
intramural air, air in the mesenteric and portal
veins and frank perforation which are all ominous
signs.

88.  Intramural air in the form of parallel streaks of gas
along the bowel wall or as rings may also be seen
in infants with necrotizing enterocolitis.
 This appearance should not be confused with the
bubbly appearance of pneumatosis coli which is a
benign condition affecting the colon in adults.

89.  The causes of intestinal obstruction vary with the age of the
patient.
 In neonates and infants, the usual causes of obstruction
are congenital conditions such as :
1. hypertrophic pyloric stenosis,
2. duodenal stenosis or atresia,
3. ileal atresia etc.
a) In young children,intussusception or Ladd’s bands are
common causes of
b) obstruction.
c) Intussusception may be seen as a mass-like soft tissue
shadow with a crescent of gas surrounding the leading edge.
d) A barium examination will reveal the coil-spring appearance
of the intussuscepiens with the “claw” sign

90. 90
There is a prominent crescent sign in the left upper quadrant with
a subtle target sign in right upper quadrant.

91. 91
Intussusceptions in the left upper
quadrant on this plain film of an
infant with pain vomiting

95.  In adults, adhesions and hernias account for
more than 80% of small bowel obstructions.
 Other causes include an intraluminal obturation
by neoplasm, gallstone or bezoar or a volvulus
due to twisting of the gut around its mesentery.

96. Gall stone ileus
 This is a mechanical obstruction
caused by the impaction of one or
more gall stones in the intestine,
usually in the terminal ileum, but
rarely in the duodenum or the
colon.
The commonest radiological signs to
be observed are :
1- A gas shadow within the bile ducts
and/ or the gall bladder.
2- Complete or incomplete intestinal
obstruction.
3- An abnormal location of an already
observed gall stone.

98. Air in
biliary
tree
Gallstone Gallstone Ileus

99. Large bowel obstruction
 The commonest cause is carcinoma, of which
about 60% are situated in the sigmoid colon.
The radiological appearance of large bowel
obstruction depends on the state of
competence of the ileocecal valve :
- TYPE 1A:the ileocecal valve is competent
leading to dilated gas filled colon with its
haustral markings and a distended thin-walled
cecum but no distension of small bowel., this
can lead to massively distended cecum, which
is in then at a higher risk of perforation
secondary to ischemia ( transverse
cecal diameter of 9 cm had been suggested
as the critical point above which the danger of
perforation exists).

100. As this type progresses, small bowel
distention occur (type 1B), with a
radiological appearance identical to that of
paralytic ileus .
In TYPE II obstruction, the ileocecal
valve is incompetent and the cecum and
ascending colon are not distended, but the
back pressure from the colon extends into
the small bowel which may simulate small
bowel obstruction.

101. Cecal volvulus
(Right colon volvulus)
 This account for less than 2% of
adult intestinal obstruction
( young age group).
 The diagnosis of acute cecal
volvulus is rarely made on
clinical ground alone, and so
radiological diagnosis become
much more important & it is
usually comprises a distended
lower abdominal viscus with
one or two haustral markings,
concomitant small bowel
dilatation & a collapsed left half
of the colon.
 Note: identification of gas filled
appendix confirm the diagnosis.

103. Sigmoid volvulus
 This is the classic volvulus,
occurring in old, mentally
subnormal patients.
 It is usually chronic with
intermittent acute attacks.
 Radiological signs :
 inverted U shaped
distended loop which is
devoid of haustra
(ahaustral).
 Liver or left flank overlap
signs.
 Apex of the volvulus above
T10.
 Air fluid ratio greater than
2:1.

104. Sigmoid volvulus
`bird of prey' sign
chronic volvulus.

105. Contrast failed to progress beyond the
recto-sigmoid junction. At this point, there
is smooth, curved tapering like a bird's
beak ("bird of prey sign")

106. Intestinal obstruction
 Dilated gas filled bowel loops with air-fluid levels
proximal to the obstruction
 Paralytic ileus-both SB and LB are dilated
 “String of beads” sign-Mechanical obstruction
 Thumb printing due to sub mucosal edema-
Ischemia
 Intramural air-Necrotizing enterocolitis
 “Coffee bean” appearance- Sigmoid volvulus

107. Toxic Megacolon
 Toxic megacolon is an acute transmural fulminant
colitis which can occur as a complication of any
colitis.
 most commonly seen with ulcerative colitis (1.6-
13% of
cases).
 Plain radiographs show marked colonic
dilatation(> 8 cm) particularly of the transverse
colon as this is the least dependent part of the
large bowel in the supine position.
 The wall has a shaggy appearance with mucosal
islands or pseudopolyps with absence of haustra
due to profound inflammation and ulceration.
 Theremay be air-fluid levels and small bowel

108. Toxic megacolon

109.  CT shows the distended colon filled with air, fluid
and blood with a distorted or absent haustral
pattern and irregular, nodular wall. There may be
presence of intra-mural air or blood

111. Other conditions
 Gangrenous cholecystitis -intraluminal and
intramural air
 Sentinel loop, gasless abdomen and colon cutoff
sign in Pancreatitis
 Extraluminal mottled gas in Abdominal abscess
 Gas in perinephric region – Emphysematous
pyelonephritis
 Ureteric colic – Urolithiasis

115. USG and CT
 An ileus may not be appreciated on a plain
abdominal film if bowel loops are filled with fluid
only without intraluminal air.
 Alternatively if a plain abdominal film does
indicate an ileus then sonography or CT are
usually needed to identify its cause.

116. APPENDICITIS

117. Appendicitis plain radiograph
 Fluid levels localized to the caecum and terminal
ileum, indicating inflammation in the right lower
quadrant
 Localized ileus with gas in the cecum, ascending
colon and terminal ileum
 Increased soft tissue density of the right lower
quadrant
 Blurring of the right flank stripe and presence of a
radiolucent line between the fat of the peritoneum
and tansverus abdominis
 Fecolith in the right iliac fossa
 Gas filled appendix
 Blurring of the psoas shadow on the right side.

120. Appendicitis usg
 A normal appendix has a maximum diameter of 6
mm, is surrounded by homogeneous non-
inflamed fat, is compressible and often contains
intraluminal gas.

122. Appendicitis

124. Appendicitis
General CT findings for acute appendicitis include:
1. Dilated appendix greater than 6 mm or visualization
of an appendicolith with an appendix of any size
2. Peri-appendicial fat stranding

127. This image of an acute abdomen (arrow)
displays periappendicial stranding and
dilattion of its terminal portion .
For comparison, this image of a normal
appendix can be visualized at the
ileocecal junction. Also notethe fat
ventralcontaining heria

128. Inflammation- Cholecystitis
Acute cholecystitis is inflammation of the
gallbladder
usually from impaction of a gallstone within the
cystic or common bile duct.
 Plain radiograph:
 Gallstones seen in 20%
 Duodenal ileus
 Il eus of hepatic flexure of colon
 Right hypochondrial mass due to enlarged
gallbladder
 Gas within the biliary system

129. Ultrasound is the preferred imaging method to
confirm cholecystitis in the appropriate clinical
setting.
sonographic signs include
 calculi (in 95%)
 distension of the gallbladder
 edematous wall,
 mucosal irregularity,
 intramural gas and/or pericholecystic
collection
Doppler: increased mural colour uptake

130. Acute calculous cholecystitis:
Calculus obstructs the cystic duct
The trapped concentrated bile irritates the gallbladder wall,
causing increased secretion, which in turn leads to
distention and edema of the wall.
Rising intra luminal pressure compresses the vessels,
resulting in thrombosis, ischemia, and subsequent
necrosis and perforation of the wall.

131. CT findings of cholecystitis include:
 wall thickening,
 pericholecystic stranding,
 GB distension,
 pericholecystic fluid, subserosal edema,
 high attenuation bile and sloughed membranes,
 gas or septations within the gallbladder
Complicated cases may reveal perforation or
hepatic abscess formation.

134. MRI IS COMPLEMENTORY TO CT
AND USG IN
 Demonstrating impacted calculi in the
gallbladder neckor cystic duct which are
often difficult to detect on US.
 Also, conditions causing acalculous
cholecystitis like adenomyomatosis, gall
bladder polyp, malignant neoplasm or
other cancers can be depicted on mr

135. Thickening of gallbladder wall
Cholelithiasis.

138. Complications of acute cholecystitis include:
 empyema,
 gangrenous cholecystitis,
 Gallbladder perforation and
 emphysematous cholecystitis.

139.  Empyema: occurs when pus fills the
distended and inflamed GB,typically in diabetic
patients.
 On US and CT, pus resembles sludge. Heavily
T2-weighted images are sensitive in
demonstrating purulent bile as a dependent
hypointense layer relative to normal bile.

142.  Gangrenous cholecystitis : is an
advanced, severe form of acute cholecystitis, seen
more common in elderly men.
 It results from marked distension of the GB with
resultant increase in tension in the wall.
 Associated inflammation leads to ischemic necrosis.
US reveals heterogenous or striated thickening of GB
wall or intraluminal membranes representing
desquamated mucosa.
 US findings typical of uncomplicated acute
cholecystitis may be absent in this subset of patients:
GB wall thickness may be less than 3 mm
 CT features consist of:
 intraluminal membranes, irregular wall,
pericholecystic
 fluid/abscess and lack of mural enhancement.

143. Gall bladder perforation :
 most often a complication of acute gangrenous
cholecystitis.
 blood supply is poor in the region of fundus, this is the
most common site of perforation.
 Perforation can be classified into 3 types:
A)acute free perforation into peritoneal cavity,
B) subacute perforation with pericholecystic abscess and
C) chronic perforation with a cholecystoenteric fistula.
 Subacute perforations are the most common. Following
perforation,
 US, CT and MR show complex pericholecystic
 fluid collections and the wall of GB can appear focally
 disrupted.

145.  Emphysematous cholecystitis :
 rare form of acute cholecystitis seen in patients
with diabetes and peripheral atherosclerotic
disease.
 The majority of patients are between 50-70 years.
 US demonstrates intraluminal and intramural gas
as highly echogenic foci.
 CT is the most sensitive and specific imaging
modality to identify gas in the lumen or wall.

148. ACUTE PANCREATITIS
 Acute pancreatitis refers to acute inflammation of
the pancreas.
 Causes
 Gallstones (most common)
 Alcohol abuse, usually chronic
 Trauma, more often penetrating
 Drug-induced
 Anatomic abnormality
 ERCP-induced
 Infectious, especially post-viral in children
 Vasculitis
 Idiopathic

149. ACUTE PANCREATITIS
 Pathological changes are edema,
hemorrhege,lnfarction,fat necrosis followed
by acute suppuration
 Inflammatory processes tend into gastro
colic ligament or paraduodenal areas- follow
route of mesentry or extend out of
peritoneum into perirenal space.
 Lot of radiological signs described, but
many are of little value in diagnosing
individual cases.

150. Plain film changes-
 Chest x-ray-
o Left sided pleural effusion
o Splinting of left hemidiaphragm
o Basal atelactasis
 Abdominal film-
o Duodenal ileus
o Gasless abdomen
o “colon cut off” sign
o Renal “halo” sign
o Absent left psoas shadow
o Indistinct mottled shadowing
o Sentinel loop
o Intrapancreatic gas-abscess/ enteric fistula
150

151. The abrupt termination of gas within the proximal colon at the level
of the radiographic splenic flexure, usually with decompression of
the distal colon

152. A sentinel loop is a focal area of adynamic ileus close to an intra-abdominal
inflammatory process. The sentinel loop sign may aid in localizing the source of
inflammation

153.  Later stages- pancreatic pseudocyst visible on
plain film as large soft tissue mass
 Pleural effusions, mainly left sided.

154. A/c pancreatitis
 Early stages-USG is preferred
 USG reveals enlarged hypoechoic pancreas with
peripancreatic fluid,+/- cholelithiasis
 Also in follow up of fluid collection or pseudocyst
formation.
 CECET – modality of choice- for diagnosis,detect
extrapancreatic,intras abdomial pathology
 For staging of severity-CTSI

155. CT Findings typical of pancreatitis include:
1. An enlarged pancreas with infiltration of the
surrounding fat
2. Peripancreatic fluid collections can often be
seen
3. Pseudocysts, (encapsulated fluid
collections containing pancreatic secretions,
are later complications of pancreatitis)

158. MRI
 Recent improvements in resolution and faster
breath hold sequences have drastically increased
usage of MRI in abdomen.
 But not routinely used in a/c abdomen except in
situations where contrast cannot be administered
or in pregnant patients

159.  Most important objective of imaging in a/c
abdomen is
 Identify most common causes
 Choose the modality of imaging appropriately
 Diagnose or exclude common conditions

160. Notice the peripancreatic stranding (bars) as well
as the fluid thickening of the interfascial space

161. A common complication
of pancreatitis is the
development of
pancreatic necrosis.
Lack of gland
enhancement following
IV contrast
administration is
diagnostic. When over
half the pancreas
becomes necrosed,
the mortality rate may
reach as high as 30%.

163. Pancreatic necrosis

164. Pancreatic pseudocyst

166. Intra-Abdominal Abscess
 A localized collection of pus can occur anywhere in
the abdomen:
 in the parenchyma of solid organs, in the peritoneal or
extra-peritoneal spaces. Early detection, may be
seen. At times, the abscess may have a solid
appearance.
 Color Doppler demonstrates peripheral
hypervascularity.
 CT will show a low attenuation fluid collection with
mass effect and peripheral rim enhancement with or
without gas bubbles or an air-fluid level.

168. OTHER CAUSES OF ACUTE
ABDOMEN

169. Sigmoid diverticulitis
 If the pain is located in the LLQ main concern is
sigmoid diverticulitis.
In diverticulitis sonography and CT show
diverticulosis with segmental colonic wall
thickening and inflammatory changes in the fat
surrounding a diverticulum.
 Complications of diverticulitis such as abscess
formation or perforation, can best be excluded
with CT.

171. Diverticulitis

172. A case of diverticulitis showing a thickened sigmoid colon and a diverticulum

174. Mesenteric lymphadenitis
 A common mimicker of appendicitis.
 It is the second most common cause of right lower
quadrant pain after appendicitis.
 It is defined as a benign self-limiting inflammation of
right-sided mesenteric lymph nodes without an
identifiable underlying inflammatory process,
occurring more often in children than in adults.
 This diagnosis can only be made confidently when a
normal appendix is found, because adenopathy also
frequently occurs with appendicitis.

176. Epiploic Appendagitis
 Epiploic appendages are small adipose
protrusions from the serosal surface of the colon.
 An epiploic appendage may undergo torsion and
secondary inflammation causing focal abdominal
pain that simulates appendicitis when located in
the right lower quadrant or diverticulitis when
located in the left lower quadrant.
 The characteristic ring-sign corresponds to
inflamed visceral peritoneal lining surrounding an
infarcted fatty epiploic appendage.

177. Plain radiograph
 Calcifications in acute
appendagitis

178. USG
 rounded, noncompressible, hyperechoic mass,
without internal vascularity, and surrounded by a
subtle hypoechoic line 5. They are typically 2-4 cm in
maximal diameter.

180. Renal Colic

181. Distal ureteral stone lead ing to right
hyrdronephrosis in above image
Ureteral junctional stone
Renal Colic

182. Renal stone right sided hydronephrosis
Renal Colic

184. Urolithiasis

185. Inflammation- Colitis
Colitis, or inflammation of the colon, is a frequent
cause of abdominal pain.
Specific entities which produce inflammatory
thickening of the colon include:-
Diverticulitis, inflammatory bowel disease,
pseudomembranous colitis, and other bacterial
infections (i.e. typhlitis).

187. This example of colitis shows thickening of the colon
and pericolonic stranding typical of inflammation.

188. Thickening of sigmoid colon due to pseudomembranous colitis

189. MESENTRIC ISCHEMIA
 Acute occlusion of the superior
mesenteric artery (SMA) due to embolus
is the most common cause of
mesenteric ischemia accounting for
nearly 50% of cases due to
 Thrombosis of the SMA or the superior
mesenteric vein (SMV) are responsible
for another 10-20% of cases.

193.  The manifestation may range from a self-limiting
superficial ischemia involving the watershed zones to
a diffuse ischemic injury to the entire bowel - “shock
bowel”.
 There are three stages of acute mesenteric ischemia:
 In the first stage, there is mucosal involvement
with necrosis, ulcerations and/or hemorrhage. The
injury is superficial and will eventually heal
completely.
 In stage II, there is necrosis of the deep
submucosal and muscular layers which may lead
to the development of fibrotic strictures.
 Stage III ischemia represents transmural bowel
necrosis which requires immediate surgical
intervention. The imaging appearance in a given

194.  Plain films reveal the characteristic thick-walled
dilated loops with thumb-printing.
 Intramural air or porto-mesenteric air is also
rarely visualized on the plain radiograph.
 MDCT angiography is the modality of choice for
the evaluation of bowel ischemia
 The arterial occlusion/narrowing as well as the
venous occlusion can be readily detected.
Involvement of the vasa recta (Coombs’ sign)
may be seen in small vessel vasculitis

196.  In addition, involvement of a long segment of
bowel or both small and large bowel with skip
segments are features of small vessel disease.
 The most common finding of mesenteric ischemia
is bowel wall thickening though this feature
strongly depends on the degree of bowel
distension. Mural thickening is commoner with
ischemic colitis and with veno-occlusive disease
but is rare in arterio-occlusive disease where the
involved segment of bowel may show dilated,
fluid-filled loops with paper-thin walls

197.  The bowel wall may show a striated appearance
due to the presence of sub-mucosal edema or
hemorrhage. In complete arterial occlusion, there
can be absence of the normal enhancement of
the bowel wall. Conversely, in non-occlusive
ischemia there can be abnormal persistent mural
enhancement. The target sign is seen when there
is hyperenhancement of the mucosa and
submucosa due to hyperemia and hyperperfusion
with mural edema

198. THMB PRINTING IN ISCHEMIC
COLITIS

199. SMA thrombosis

200. VASCULAR CAUSES
 Vascular conditions that may present as acute
abdomen include rupture of an aortic aneurysm,
spontaneous aortic occlusion, acute hemorrhage
and hepatic or splenic vascular occlusion
 average age at the time of diagnosis being 65-70
years.
 Most abdominal aortic aneurysms are true
aneurysms and
 occur below the level of renal arteries. An
abdominal aortic aneurysm is defined as an aortic
diameter of 3cm or more42 while a diameter of
5.5 cm or more warrants urgent intervention.

201.  Multidetector CT is the modality of choice for
evaluation of acute aortic syndrome.
 The most common finding of rupture of aortic
aneurysm is a retroperitoneal hematoma adjacent
to the aneurysm
 . Other CT features may include active
extravasation of contrast, extension of periaortic
blood into perirenal or pararenal spaces or the
psoas muscle or peritoneal cavity

202. Aneurysms

204. Signs predictive of impending rupture
are:
 a. Draped aorta
sign – Seen with
contained leak.
The posterior
wall of aorta
cannot be
defined due to
close application
and lateral
‘draping’ of the
aneurysm
around the
adjacent

206.  b. Increase in aneurysm size – A patient with a
very large aneurysm (> 7cm diameter) who
presents with acute aortic syndrome has a high
likelihood of aneurysm rupture. Also, a rate of
enlargement of >10 mm per year warrants
surgical repair.
 c. Thrombus-to-lumen ratio - This ratio decreases
with increasing aneurysm size. A thick
circumferential thrombus is protective against
rupture.
 d. Focal discontinuity in intimal calcification.

207.  e. Hyperattenuating crescent sign due to
hemorrhage in either the peripheral thrombus or
aneurysm wall.

208.  Acute abdominal hemorrhage may result due to
ruptured aneurysm in a case of polyarteritis
nodosa, ruptured tumor (usually renal cell
carcinoma) or in a patient on anticoagulant
therapy.
 Non-contrast CT demonstrates a hyperdense
collection at the site of hemorrhage.
 MDCT angiography can accurately delineate the
site and cause of hemorrhage.

209.  Rare causes of acute abdomen include:
 hepatic vein thrombosis (acute Budd-Chiari
syndrome) and
 portal vein thrombosis.
 US in the acute phase may show liver enlargement,
partial or complete inability to visualize hepatic veins,
intraluminal hepatic vein echogenicity or thrombosis,
marked narrowing of intrahepatic IVC and ascites.
 Color Doppler: Absence of flow or flow in an
abnormal direction in all or part of the hepatic veins
may be seen.
 CT and MR are complimentary techniques for
definitive diagnosis which provide a more complete
evaluation of the hepatic parenchyma, hepatic veins
and IVC.

210. Pelvic Disease

211. Signs of a ruptured ectopic
pregnancy on ultrasound
 an inhomogeneous adnexal mass,
 pelvic fluidor hematoma,
 decidual reaction without intrauterine gestation sac,
in the presence of a positive pregnancy test.
 Visualization of an echogenic adnexal ring separate
from the ovary that has prominent peripheral flow on
color Doppler is highly suggestive of ectopic
gestation.
 Corpus luteum is a useful guide while looking for an
ectopic pregnancy and is usually seen in the
ipsilateral ovary in 70-85% cases. Using transvaginal
ultrasound, the live embryo can be detected in upto
17% of all ectopic pregnancies.

215. FIBROIDS
 Fibroids may present with acute pain if there is
torsion or degeneration of a submucosal or
subserosal fibroid.
 On imaging, uterine enlargement with a focal
mass or contour deformity are seen.
Degenerated fibroids may have a cystic
appearance.

217. MRI
 Haemorrhagic fibroid degeneration. This patient, known to have
uterine fibroids, presented to the accident and emergency
department with low-grade pyrexia, tachycardia and acute lower
abdominal pain. a Sagittal T2 image demonstrates a large uterine
fibroid with high signal intensity centrally with a very low signal
intensity rim suggestive of peripheral haemosiderin. b Axial T1 with
fat-saturated image shows high signal intensity within the fibroid
consistent with haemorrhage (black arrow). c Axial T1 with fat
saturation following gadolinium administration demonstrates lack of
enhancement within the fibroid (black arrow), consistent with
infarction. The surrounding myometrium enhances normally (white

218. OVARIAN TORSION
Ovarian torsion usually occurs in children and is
attributed to excessive mobility of the ovary.
In adults,a cyst or mass, frequently a cystic teratoma, is present
in the ovary undergoing torsion.
Sonographic findings :
1. enlarged ovary with peripherally distributed follicles,
2. an associated cyst or mass
3. diminished or absent central venous flow on Doppler.
CT:
deviation of the uterus to the twisted side,
obliteration of fat planes and an enlarged ovarydisplaced from its
adnexal location is seen.
Contrast enhanced CT may show surrounding enhancing blood
vessels due to congestion.

221. Hemorrhage into a corpus luteal or
follicular cyst
 manifest with abrupt onset of pelvic pain.
 If the cyst ruptures, associated hemoperitoneum
can be life threatening.
 On imaging, hemorrhagic ovarian cysts can
mimic a variety of solid and mixed solid-
cysticmasses.
 A fluid-fluid level may be present.
 On CT, high attenuation components are usually
seen due to hemorrhage.

223.  A CT predominantly cystic lesion.
MRI.
On MRI the hemorrhagic content will make endometrioma appear
bright on T1-weighted images.
On T1-fatsat images an endometrioma will remain bright.
This in contrast to teratomas, that are also bright on T1 but dark on
T1-fatsat images.
On T2-weighted images endometriomas typically show 'shading'

224. Ovarian vein thrombosis
Pregnancy increases the risk for venous
thrombosis
due to stasis, alteration in coagulation factors and
by nearly tripling the diameter of the ovarian
veins.
In 90% of cases, the right ovarian vein is involved
due to dextrotorsion of the uterus.
OVT may be diagnosed by US, CT or MRI,
however, CT is the modality of choice and
demonstrates a low attenuation thrombus in
lumen of ovarian vein

227. MRI IN ACUTE ABDOMEN

228.  Although US is the first-line investigation for
suspected appendicitis in a pregnant patient,
 MR imaging is better than CT as the second-line
imaging modality when US results are nondiagnostic
or equivocal.
 Although the safety of MR imaging to the fetus has
not been proved, no proved human teratogenic or
carcinogenic effects of MR imaging have been
described in the literature.

232. ADNEXAL TORSION
 The suitability of MR imaging is equal to that of
CT in patients in whom an adnexal lesion is
believed to be present.
 according to the ACR criteria; however, in
postmenopausal women with a complex or solid
adnexal mass depicted at US,
 MR imaging is considered superior to CT.
 MR imaging and CT are used mainly when the
presence
of acute torsion with a pelvic mass is suspected
or when the signs and symptoms are suggestive
of a subacute or chronic condition.

233. The MR imaging features of ovarian torsion:
 which have been well described, include ovarian
enlargement with stromal edema.
 The common CT and MR imaging features of
adnexal torsion include thickening of the twisted
fallopian tube, smooth thickening of the wall of
the cystic ovarian mass, ascites, and uterine deviation
to the side of torsion

235. PID