The ‘acute abdomen’ is a clinical condition
characterized by severe non-traumatic abdominal
pain, requiring the clinician to make an urgent
3. Clinical presentation
-The clinical presentation of patients with an
acute abdomen is often nonspecific.
-Both surgical and nonsurgical diseases may
present with a similar clinical history and
-Findings may be normal in patients who need
emergency surgery (such as appendicitis) and
may be abnormal in patients without a surgical
disease (like salpingitis).
5. Role of imaging
• To help surgeon decide whether or not a patient
with acute abdomen needs to have a surgery
• Whether operation needs to be done immediately
or time can be spent on resuscitation or further
• To support the clinical findings.
• To narrow down the differential diagnosis
7. Role of plain radiograph
A plain abdominal film has a limited value in the
evaluation of abdominal pain.
A normal film does not exclude an ileus or other
pathology and may falsely reassure the clinician.
Plain film is useful for-
•Radioopaque stone / calcification detection
•Air / air-fluid pattern detection
10. Role of USG in acute abdomen
• Real time USG allows confirmation of palpable masses
and focal point of tenderness
• Evaluation of visible gas and fluid
• Perienteric soft tissue mass
• Evaluation of peristalsis
• Acute appendicitis
• Acute cholecystitis
• No ionizing radiation
11. Focused assessment with sonography for
trauma ( FAST)
• Rapid bedside ultrasound examination performed by
surgeons, emergency physicians as a screening test for
blood around the heart (pericardial effusion) or
abdominal organs (hemoperitoneum) after trauma.
• The four classic areas (4P) that are examined for free
fluid are -
Perihepatic space (also called Morison's pouch or the
• With this technique it is possible to identify the
presence of intraperitoneal or pericardial free fluid.
• In the context of traumatic injury, this fluid will usually
be due to bleeding.
12. Role of CT scan
• Most sensitive method for the detection of peritoneal
• Confirm the diagnosis of intestinal obstruction
• H/O previous abdominal malignancy
• Extra luminal disease
• In acute pancreatitis, renal colic, leaking abdominal
aneurysm, Intra abdominal abscess
• Before imaging- clinical history, relevant physical
examination & laboratory investigation findings,
top diagnosis and possible differentials have to
• This helps in choosing the appropriate imaging
modality as well as narrows down the area to be
We may follow this following two step approach-
• Confirm or exclude the most common diseases.
• Screen for general signs of pathology.
18. ACUTE Cholecystitis
Occurs when a calculus
obstructs the cystic duct. The
trapped bile causes
inflammation of the
U S G is the preferred
imaging method for the
evaluation of cholecystitis,
also allowing assessment
of the compressibility of
19. Acute cholecystitis
Signs of acute cholecystitis on
Usually insensitive for acute
• Gallstone seen in
• Duodenal ileus
• Ileus of hepatic
flexure of colon
• Right hypochondrial
mass due to enlarged
• Gas within the biliary
22. One or two tube-like branching
lucencies in the RUQ, confined to
location of major bile ducts
23. “Normal” if Sphincter of Oddi incompetence
Previous surgery including sphincterotomy or
transplantation of CBD
■ Gallstone ileus: gallstone erodes through wall of GB
into the duodenum producing a fistula between the
bowel and the biliary system.
■ Stone impacts in small bowel = mechanical SBO.
24. Portal venous air
within 2 cm of
the liver capsule
Air is peripheral
rather than central
25. Ultrasound : The mainstay of imaging in cholecystitis
• Gallbladder wall thickening (>3 mm), which may be poorly
• Impacted calculi in the gallbladder neck or cystic duct.
Gallstones are visualized as echogenic foci with posterior
• Biliary sludge may be seen as echogenic debris layering in
• Pericholecystic fluid.
• Positive sonographic Murphy’s sign
27. CT is not routinely required but may be utilized as part
of the investigation of nonspecific abdominal pain or
to assess for secondary complications of cholecystitis.
• Gallbladder wall thickening (>3 mm).
• Biliary calculi may be visualized as foci of high attenuation
within the gallbladder.
• Inflammatory stranding in the pericholecystic fat
• Pericholecystic fluid/focal enhancing collections will
appear as a low-attenuation collection surrounding the
• Locules of free gas adjacent to the gallbladder secondary to
• Cholecystoenteric fistulae are rare.
At sonography and CT the appendix is seen as
a blind-ending nonperistaltic tubular structure
arising from the base of the cecum.
May mistake a small bowel loop for the
The outer-to-outer diameter of the appendix is
the most important imaging criterion.
31. Signs of acute appendicitis in plain film
• Appendix calculus (0.5-6 cm)
• Sentinel loop-dilated atonic ileum containing a fluid level
• Dilated caecum
• Widening of the properitoneal fat line
• Blurring of the properitoneal fat line
• Right lower quadrant haze due to fluid and oedema
• Scoliosis concave to the right
• Right lower quadrant mass indenting the caecum
• Blurring of the right psoas outline-unreliable
• Gas in the appendix-rare, unreliable
34. Sign of acute appendicitis in ultrasound
• Blind-ending tubular structure at the point of tenderness
• Diameter 7 mm or greater
• No peristalsis
• Appendicolith casting acoustic shadow
• High echogenicity non-compressible surrounding fat
• Surrounding fluid or abscess
• Oedema of caecal pole
• Hypervascularity on power Doppler
37. Ultrasound images showing an anechoic blind-ending tubular structure
measuring 10mm in diameter in the right iliac fossa (RIF): this was
found to be non-peristaltic and non- compressible.
An echogenic round body, with posterior acoustic shadowing seen
within the tubular structure, in keeping with an Appendicolith.
38. CT findings in acute appendicitis
90% diagnostic accuracy to detect acute appendicitis
• An appendix measuring greater than 6 mm in diameter
• Failure of the appendix to fill with oral contrast or air up to
• An appendicolith
• Enhancement of its wall with intravenous contrast
• Surrounding inflammatory changes include increased fat
attenuation, fluid, inflammatory phlegmon, caecal
thickening, abscess, extraluminal gas and
39. Acute appendicitis. CT
showing an appendix which
contains a dense
Appendix inflammatory mass. CT
shows soft- tissue density in the
right iliac fossa containing an
42. It is a very common condition in older patients
Diverticula- A characteristic muscle abnormality in
the sigmoid colon with typical ‘out pouching’ from
the colonic wall
Diverticulosis - presence of diverticula
Diverticulitis – refers to inflammatory changes
within one or more diverticula
43. USG 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
46. Screen for general signs of pathology-
Free air/ Air-fluid pattern
Bowel wall thickening
Rupture of a hollow viscus-
• Perforated peptic ulcer
• Perforated diverticulitis (usually seals off)
• Perforated carcinoma
Post-op - 3-7 days normal, should get
less with successive studies
Free air / Pneumoperitoneum
49. Abdomen erect / Upright chest / Left lateral decubitus /
Supine abdomen ?
Uprigh chest P/A Left lateral decubitus
50. The patient should be positioned sitting
upright for 10-20 minutes prior to
acquiring the erect chest X-ray image.
This allows any free intra-abdominal gas to rise
up, forming a crescent beneath the diaphragm.
It is said that as little as 1ml of gas can be
detected in this way.
57. The triangle sign
refers to small
triangles of free gas
that can typically be
the large bowel and
58. May mimic air under
Look for haustral folds
Get left lateral
decubitus to confirm
In patients who have
cirrhosis or flattened
diaphragms due to lung
hyperinflation, a void is
created within the upper
abdomen above the liver.
This space may be filled by
bowel. If this bowel is air
filled then it may mimic free
62. On Plain films
• Dilated gas & fluid filled loops of small bowel.
• Multiple fluid level
• Dilated fluid-filled loops of small bowel may be
identified as oval or round soft tissue densities that
changes with position.
• Absent or little air in large bowel
65. String of pearls sign in a patient with small-bowel obstruction (SBO).
Erect radiograph of the abdomen demonstrates a row of small air
bubbles (arrows), which represents air trapped between the valvulae
66. Role of USG in bowel obstruction
• Presence of abundant gas produces images of non diagnostic
• USG may be used for evaluation of
• GIT caliber
• Peristaltic activity
• Site of obstruction
• Gut wall morphology
• Extrinsic soft tissues
68. Role of CT scan
• CT can confirm the diagnosis of SBO, indicate the location
of the obstruction
• Fluid filled bowels are clearly visible on CT
• Indicated with H/O –
- previous abdominal surgery
- extra luminal disease
• Effective at detective hernias
• A focal calibre change from dilated to collapsed bowel, the
transition point, indicates the level of obstruction.
• The small bowel is considered dilated when its diameter is
greater than 3 cm.
69. The 'Small Bowel Feces Sign' (SBFS) - seen
at the zone of transition thus facilitating
identification of the cause of the obstruction.
Small bowel faeces sign
70. SBO due to gall stone ileus
• Is mechanical bowel obstruction due to gall
stone/s in the intestine
• 2% of SBO
Signs of gall stone ileus
• Gas within the bile ducts and / or the gall bladder
• Complete or incomplete SBO
• Abnormal location of gall stone
• Change in position of gall stone
Invagination or prolapse of a
segment of intestinal tract (
intussusceptum) into the lumen of
the adjacent intestine (
90% are ileocolic and ileo-ileocolic.
• Severe colicky pain and vomiting.
• Initial stools passed at the start
of symptoms are unremarkable;
blood and mucus
(‘redcurrant jelly’) stools are passed
73. Plain film
• There are multiple gas filled
loops of dilated
• Soft tissue mass in right iliac
74. Seen in infants
Represents dilatation of the proximal duodenum and
It is seen in both radiographs and ultrasound, and
can be identified antenatally
Seen in duodenal atresia.
77. Plain film signs of large bowel obstruction
• Depends on the state of competence of ileo caecal
• Distended bowel is few in number
• Large: above 5.0 cm diameter
• Large amount of air is peripheraly placed
• Haustra : thick and widely separated
• CT confirms obstruction with a colonic diameter
of >5.5 cm (9 cm in the caecum) considered
• Identification of a transition point indicates the
level of obstruction.
• CT clearly demonstrates intramural gas,
perforation and abscess formation.
80. Colonic carcinoma
• Focal irregular bowel-wall thickening with proximal
• There may be inflammatory stranding in the
Axial and coronal images demonstrating large-bowel
obstruction (asterix) secondary to a colonic carcinoma
in the distal descending colon (arrow).
81. Contrast enema maybe helpful
• To differentiate pseudo-obstruction from
• To localize the point of obstruction
• To diagnose the cause of obstruction e.g. tumour,
83. Identification of loop in sigmoid volvulus
Massively dilated sigmoid loop (an air-filled, dilated viscus)
arising from the pelvis.
• Ahaustral margin
• Left flank overlap sign
• Apex at or above T10 level
• Apex under the left hemidiaphragm
• Inferior convergence on the left (upper sacral
• Liver overlap sign
• Inverted U -shaped appearance, with the limbs of the
sigmoid loop directed toward the pelvis
87. Caecal volvulus
• Associated with degree of malrotation
• Accounts for less than 2% of adult intestinal obstruction
• Age -30-60 years
• Pole of the caecum and the appendix lie in LUQ(50%)
• Caecum twists in axial plane and lies in the central part
on right half of abdomen(50%)
• One or two haustral markings can usually be identified
• Seen as large gas filled or fluid filled viscus
• Identification of adjacent gas filled appendix confirms the
• Left half of colon is usually collapsed