acute abdomen conditions in radiology and their evaluation
acute pancreatitis, cholicystitis, pelvic pathology, mri evaluation , intra abdominal abcess, plain radiography evaluation of acute abdomen, vascular causes of acute abdomen, causes of 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
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
23. Large vs. Small Bowel
Large Bowel
Peripheral
Haustral markings don't extend
from wall to wall
Small Bowel
Central
Valvulae extend across lumen
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
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
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.
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
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
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
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
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.
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.
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
66.
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
68.
69. Mechanical SBO
Key Features
Dilated small bowel
Little gas in colon, especially
rectum
Key: disproportionate
dilatation of SB
SBO
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
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).
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.
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.
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.
102.
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.
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
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
110.
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
112.
113.
114.
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.
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.
118.
119.
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.
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
125.
126.
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.
132.
133.
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
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.
140.
141.
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.
144.
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.
146.
147.
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)
156.
157.
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%.
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.
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.
172. A case of diverticulitis showing a thickened sigmoid colon and a diverticulum
173.
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.
175.
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.
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.
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).
186.
187. This example of colitis shows thickening of the colon
and pericolonic stranding typical of inflammation.
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.
190.
191.
192.
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
195.
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
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
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
205.
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.
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.
212.
213.
214.
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.
216.
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.
219.
220.
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.
222.
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
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.
229.
230.
231.
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