Transcript IMAGING OF ACUTE ABDOMEN


“Acute abdomen” is a term used to
encompass a spectrum of surgical, medical
and
gynecological
conditions
(intraabdominal process), ranging from the trivial
to the life threatening, which require hospital
admission, investigation and treatment
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Assesing the patient with an acute abdomen
need
many
investigation
including
laboratory test and imaging studiesplain
photo, US, CT and contrast study .
Plain abdominal films: erect chest film,
supine, and upright (optional:left lateral
decubitus)
 Abdominal US
 Abdominal CT
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Plain abdominal film
Table 1 Plain abdominal film
Erect Chest
Best for free air under
right diaphragm
Supine Abdomen
Best for abdominal
detail: Organs, bones
and joints,
calcifications, fat and
gas pattern
Erect Abdomen
For air-fluid levels and
little else
Left Lateral Decubitus
Abdomen
For free air and airfluid levels
Looking
for
› Gas pattern
› Calcifications
› Soft tissue masses
Substitute
– none
Looking
for
› Free air
› Air-fluid levels
Substitute
– left
lateral decubitus
Hemorrhage
 GI perforation
 Bowel obstruction
 Inflammatory disorder
 Circulatory impairment
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Intraperitoneal hemorrhage
› Rupture:
 hepatoma
 aortic anuerysm
 ectopic pregnancy
 ovarian bleeding
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Gastrointestinal hemorrhage
› Upper GI hemorrhage
 Duodenal ulcer
 Gastric ulcer
 Hemorrhagic gastritis
 Esophageal or gastric varices ect.
› Lower GI hemorrhage
 Bleeding of colon cancer
 Ischemic colitis ect.
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US finding
› Free peritoneal fluid accumulation on the
Morison’s pouch, the rectovesical pouch, the
pouch of Douglas, and the bilateral subphrenic
space
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Abdominal CT
› CTgold standars for specific intraabdominal
pathology
Gastrointestinal perforation are serious
disorder requiring rapid diagnosis and
treatment
 Since they may be severe enough to
produce septic or hypovolemic shockrapid
decision-making for urgent laparotomy is
crucially important
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Radiological appearances:
Plain abdominal film:
- Oval/linear collection of gas:
♠ Subhepatic space
♠ Morison’s pouch
♠ Beneath the diaphragm (the cupola sign)
♠ In the centre of the abdomen over a fluid
collection (the football sign)
♠ Fissure for ligamentum teres
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Fissure for ligamentum teres
Rigler’s sign
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The first investigation when bowel
obstruction is suspected is the supine plain
abdominal X-ray, together with an erect
chest film if perforation is a possibility
 Occasionally, all the dilated bowel may be
fluid fill and not visible on a plain X-ray and
further imaging with contrast studies, CT or
US may be needed to demonstrate dilated
bowel
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Imaging aims: to confirm the presence of
bowel obstruction, define
the level
obstruction, identify the cause and detect
complications such as perforation
Extrinsic
Bowel wall
Intraluminal
Adhesions
Neoplasia
Intussusception
Hernia
Strictures:inflamma Foreign body
tory,
radiation,chemical
Volvulus
Intestinal
ischaemia
Inflammation/abscess
Malignant infiltration
(e.g. peritoenal
deposits)
Gallstone ileus
 Etiology:
- Adhesions due to previous surgery
- Strangulated hernias
- Volvulus
- Gallstone ileus
- Intussusception
- Neoplastic, etc.
Plain filmprimary investigation of choice
 Plain film of SBO:
Dilated small bowel loops:
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Tend to the central
Numerous
2.5-5.0 cm diameter
Have a small radius of curvature
Valvulae conniventes: thin, numerous, and
extend right across the bowel
› Do not contain solid faeces
Multiple fluid levels on the erect film
 String of beads sign on the erect film
 Absent or little air in the large bowel
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US:SBO
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CT sign of SBO
› Small bowel loops measuring>2.5 cm in diameter
› Identifiable focal transition zone from prestenotic
dilated bowel to post-stenotic collapsed bowel
loops
Fluid-filled loops
Bowel calibre change
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Etiology:
- Neoplastic (benign & malignant)
- Volvulus (caecal & sigmoid), etc.
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Radiological appearances:
Depends on the state of competence
of the ileocaecal valve:
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Plain-film signs of LBO:
› Dilated large bowel loops which:
 Tend to be peripheral
 Few in number
 Large: above 5.0 cm diameter
 Wide radius of curvature
 Haustra: thick and widely separated and may or
may not extend right across the bowel (compare
these features with the valvulae conniventes found
in the small bowel
 Contain solid faeces
› Caecum maybe dilated
› Small bowel may be dilated
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Contrast enema maybe helpful:
› To differentiate pseudo-obstruction and may be
indistinguishable on plain film from mechanical
of obstruction
› To localized the point of obstruction
› To diagnose the cause of obstruction e.g.
tumour, inflamatory mass
Plain film:Sigmoid volvulus
coffee bean sign
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Generalised paralytic ileus:
●Etiology:
- Peritonitis
- Post-operative
- Hypokalaemia
- General debility or infection
- Drugs: morphine
- Congestive cardiac failure, renal colic, etc.
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●Radiological appearances:
- Both small & large-bowel dilatation
- Horizontal-ray films: multiple fluid levels
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Acute appendicitis
 Acute pancreatitis
 Acute cholecystitis
 Abdominal absces
 Peritonitis
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Abdominal x-ray (AXR)
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US
› Non-specific finding
› Approximately 10%a calcified appendicolith
› Generally, the normal cannot be defined with US,
clear visualization of the appendix is suggestif of
inflammation
› Swollen, non compressible appendix greater than
7 mm in diameter with a target or bulls-eye
configuration is produced by the hypoechoic
dilated appendiceal lumen
› Assymetrical wall thickening due to phlegmonous
infiltration, an appendicolith with acoustic
shadowing
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US finding
› Echogenic hallo form by omental tissues draped
over the appendix
› Free fluid in the culdesac
› Atony in the terminal ileum with compression US
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CT finding
› 90% diagnostic accuracy to detect acute appendicitis
› With the good contrastfilling of the terminal ileum
and the cecum (oral contrast given 1 hour before
examination)
› Tubular structure 4 mm to 20 mm in diameter with a
thickened wall that enhance after administration IV
contrast medium
› Pericecal fluid collection and calcified appendicolith
Plain film:apendicolith
Severity of acute
pancreatitis
rangesmild edema
with minimal
symptoms to a severe
necrotizing process
that culminates in
multiple organ failure
 US and CT most
precisely define the
anatomic extent of
the lesions and the
detect local
complications
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Plain filmsno significant plain film
findings in up to two-thirds of patients wih
acute pancreatitis
 Plain-film signs may include:
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› Paralytic ileus in the left upper quadrant
› Generalized ileus
› Loss of left psoas outline
› Separation of greater curve of stomach from
tranverse colon
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CXR signs that may be seen include:
› Left pleura effusion
› Atelectasis of left lower lobe
› Elevated left hemidiaphragm
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US finding:
› The acutely inflamed pancreasenlarged with
decreased echogenicity and blurred irregular
margin
› Fluid collection are seen as hypoechoic areas
› US can be used to guide aspiration and the
drainage procedures, and for follow up
CTimaging investigation of choice for
acute pancreatitis, and is particularly
useful for the following:
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Confirmation of the diagnosis
Identification of necrotic gland tissue
Diagnosis of complication
Guidance of interventional procedures
CT signs of acute pancreatitis include:
› Diffuse or focal pancreatic enlargement with decreased
density and indistinct gland margins
› Thickening of surrounding fascial planes e.g. left
paranephric fascia
› Acute fluid collections, most commonly related to
pancreas though also in the lesser sac and in the left
pararenal space
› Phlegmon appears as an irregular mass spreading along
fascial planes and can be quite extensive
› Abscess
› Pseudocyst
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Approximately 85%-90% of
cases with acute
cholecystitis (AC) develop
as a complication of
cholelithiasis
Conversely, approximately
10%-20% of patients with
gallstone will require
surgery for complication,
usually cholecystitis, within
15 years after their stone
disease is diagnosed
Acalculous cholecystitis
account for 5%-15% of
cases of acute cholecystitis
(immunocompromize,
critically ill,iatrogenic,
congenital etc)
Plain filmsinsensitive for acute
cholecystitis
 Plain films signnonspesific and include:
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› Gallstone (only seen in 10%)
› Soft tissue mass in the right upper quadrant
due to distended gallbladeer
› Paralytic ileus in the right upper quadrant
USinvestigation of choice for suspected
acute cholecystitis
 US signs of acute cholecystitis include:
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› Gallstones:hyperechoic lesions with acoustic
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shadowing which are mobile
Thickening of gallbladder wall to greater than 4
mm
Hypoechoic gallblader wall due to oedema
Surrounding fluid or localized fluid collection
Distended gallbladder
Localized tenderness to direct probe pressure
CTscanning contribute little to
diagnosis of cholecystitis
 CTinvestigation of
complicatiosbiliary or pericholecystic
abscess
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Peritonitisan inflammatory or
suppurative reaction of the peritoneum
to direct irritation
 Cause:
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› Inflammatory
› Infectious
› Ischemic
Exudation,
Hematogenous,
Contiguous extension,
Iatrogenic manipulation
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Plain abdominal radiograph: cannot
provide specific
Air-fluid Levels
Stones
Ascites
Eggshell calcification
Air in Biliary tree.
Obliteration of psoas-shadow in retro- peritoneal
disease
› Right lower quadrant sentinel loops in acute
appendicitis
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USnonspecific
 Abdominal CT
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› CT signs 
 Ascites (free or encapsulated)
 Infiltration of the omentum and/or mesentery
 Thickening of the parietal peritoneum
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Angiography for ischaemia, hemorrhage
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Acute inflammatory colitis
Toxic megacolon
Pseudomembranous colitis
Ischaemic colitis
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Plain film can assess :
♠ the extent of the colitis
♠ the state of mucosa:
It can be assessed from :
- the faecal residue:
In left-sided disease, the proximal limit of
faecal residue will indicate the extent of
active mucosal lesion.
- the width of the bowel lumen
- the mucosal edge
- the haustral pattern
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A fulminating form of colitis with transmural
inflammation, extensive & deep ulceration &
neuromuscular degeneration.
Involve the transverse colon
Ro. Findings:
Mucosal islands (=pseudopolyps) & dilatation (8
cm)
Common complication:
Perforation in the sigmoid & peritonitis
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Etiology:
Vascular insufficiency & bleeding into the wall
of the colon.
Sudden onset of severe abd.pain in the early
hours of the morning, followed by bloody
diarrhoea.
In middle-aged & elderly patients.
The wall of splenic flexure & descending colon
is greatly thickened→ thumb printing (plain
films).
The right side of colon is frequently distended.
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thumb printing
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