The document discusses radiology in evaluating the acute abdomen. Key points include: - Imaging plays an important role in diagnosing the cause of an acute abdomen, which is a life-threatening situation requiring urgent diagnosis and often surgery. - Erect chest x-ray, abdominal x-rays, ultrasound, CT, and in some cases IVU, angiography or MRI may be used to identify conditions like pneumoperitoneum, intestinal obstruction, gastric dilatation, volvulus, appendicitis, cholecystitis, pancreatitis, abscesses, trauma injuries to organs like the spleen and liver. - CT is often the best initial study as it is not limited by overlying gas or tissue and

1. Radiology in acute
abdomen

2. The acute abdomen is defined as
a life threatening situation that is produced
by a variety of intraperitoneal pathologic
conditions and that requires expeditious and
accurate diagnosis, and, in most instances,
emergency surgical intervention

3. Imaging

4. ƒ Erect chest radiograph:
o Small pneumoperitoneum can be detected
o Various chest conditions may mimic an acute abdomen.
o Acute abdominal conditions may be complicated by chest
pathology
o Acts as a valuable baseline

5. ƒ Abdominal radiographs: (kv:60-65, short exposure time)
o Supine abdominal radiograph- distribution of gas
calibre of bowel
displacement of bowel
obliteration of fat lines
o Erect abdominal radiograph- fluid level and free gas
o Horizontal-ray films( erect or lateral decubitus)- free intra- abdominal air,
fluid levels
o Lateral abdominal radiograph- demonstrate calcification in an aortic
aneurysm

6. ƒ Ultrasonography- extremely effective in conditions like
acute cholecystitis, appendicitis,
gynaecological disease, intraperitoneal
fluid etc
ƒ CT- modality of choice in acute abdominal cases as it is
not hampered by overlying gas, bone or adipose tissue
ƒ IVU- in a case presenting with a renal colic
- in renal trauma
ƒ Angiography- helps to define anatomy and globally assess
major organ and vascular structures
ƒ MRI
ƒ Nuclear medicine

7. Conditions presenting as an
acute abdomen

8. Pneumoperitoneum

9. ‰ Presence of free gas in the peritoneal cavity always indicates
perforation of a viscus
‰ Commonest cause is peptic ulcer perforation, less common causes are
diverticulitis and malignant tumours.
Imaging
‰ Erect chest radiograph & left lateral abdominal radiograph
‰ Signs of free gas on the supine radiograph-
o Morison’s pouch air
o Perihepatic air
o Rigler’s(double wall) sign
o Falciform ligament
o Umbilical ligament
o Urachus
o The cupula
o Football or air-dome
‰ C.T.-most sensitive.

10. Free air under the diaphragm Rigler’s sign

11. Pneumoperitoneum

13. Intestinal obstruction

14. Gastric dilatation-
‰ Causes-
o Paralytic ileus
ƒ Post operative
ƒ Trauma
ƒ Peritonitis
ƒ Pancreatitis , Cholecystitis
ƒ Diabetic & hepatic coma
o Mechanical gastric outlet obstruction
ƒ Peptic ulceration
ƒ Antral carcinoma
ƒ Extrinsic duodenal compression
o Gastric volvulus
o Air swallowing
o Intubation
o Secondary to intestinal obstruction
o Drugs
Massive fluid filled stomach
with little or no bowel gas
beyond
Distended stomach with
fluid and gas

15. Gastric volvulus

16. o Twisting of the stomach around its
longitudinal or mesenteric axis
o Laxity of the gastro-colic, gastro-
hepatic & gastro-lienal ligament
predisposes to gastric volvulus
o In organo-axial volvulus, the
stomach twists either anteriorly or
posteriorly around its longitudinal
axis with two points of luminal
obstruction
ƒ Contrast studies reveal complete
obstruction at the lower end of
oesophagus/no passage beyond the
obstructed pylorus

17. o In mesentero-axial volvulus,
the stomach twists around the
mesentery, so that the antrum
and pylorus lie above the
gastric fundus
o Can cause complete
obstruction, strangulation and
perforation
o The fluid and air containing
dilated stomach is identified as
a spherical viscus displaced
upward and to the left with
little or no gas beyond

18. Mesentero-axial volvulus
Organo-axial volvulus

19. Small bowel obstruction

20. Extrinsic causes - adhesions
- hernias
- masses
- congenital malrotations
Intramural causes - inflammatory strictures
- ischaemia
- primary small bowel tumours
Intraluminal causes - gall stones
-foreign bodies

21. Imaging-
‰ Plain film
o Signs appear after 3-5 hours,
marked after 12 hours
o Supine abdominal X-rays- dilated
gas filled loops, identified as sausage
shaped, oval or round soft tissue
densities
o Erect films- multiple fluid level
o Horizontal ray films- ‘string of
beads’ sign

22. Dilated small bowel loops
Multiple air-fluid levels

23. ‰Contrast studies- 100ml of non-ionic contrast given orally
& further film taken at 4 hours. If no
contrast in caecum- high likelihood for surgery
‰ USG - dilated fluid-filled loops
- peristaltic activity can be
assessed
‰ C.T.- bowel calibre
- fluid filled loops
- Level & cause of obstruction
- ascitis

24. Strangulating obstruction
o Occurs when two limbs of a loop are incarcerated by a
band or in a hernia, compromising the blood supply
o Plain radiograph- soft tissue mass or pseudotumour
- gas filled loops separated by thickened
walls may resemble a large coffee bean
- if gangrene occurs, lines of gas seen in
the wall of the small bowel

25. C.T.- small bowel dilatation
- V shaped or radial fluid filled loops
- mesenteric vessels converging towards the point of obstruction
- stangulation- thickened loop with venous congestion of the
mesentery locally
- haemorrhage- increased attenuation of bowel wall
- necrosis- gas in the bowel wall

26. Gallstone ileus
o Mechanical intestinal obstruction due to impaction of
gall stones in the intestine
o Comprises about 2% of small bowel obstruction
o Signs- gas within bile ducts/ the gall bladder
- complete or incomplete small bowel obstruction
- abnormal location of gallstone
- change in position of gallstone
o C.T.- small bowel dilatation
- gas within the biliary tree
- gallstone at the point of obstruction

27. Gall stone ileus

28. Intussusception
• It is the invagination of a segment of bowel
( intussusceptum) into the contiguous segment
( intussuscipiens)
• Commonly seen in children below 2 years
• Ileocolic segment involved in 90% cases, ileoileocolic,
colocolic and ileoileal intussusception may also occur
• Usually commences in the ileum due to inflammation of the lymphoid
tissue in Peyer’s patches
• Pathological lead points – 5‐ 10 % cases
• In adults – surgery/ tumour

29. ‰ Plain radiograph-
- absence of bowel gas in RIF
- Soft tisssue mass, spherical
or oval, surrounded by
cresent of air
-“Target sign”- two concentric
circles of fat density
- Small bowel obstruction

30. ‰ Contrast examination-
- Intraluminal crescentic filling defect
- Outer surface may show a rim of barium similar to a “coiled spring”
- reduction can be achieved

31. USG-
-mass with a central echogenic area
surrounded by concentric sonolucent
rings
CT- sausage shaped mass
Ileo-colic intussusception

32. Small intestinal infarction
‰ Caused by thrombosis or embolism of the superior mesenteric artery
‰ Plain film findings:
- Gas and fluid filled dilated small bowel loops
- Multiple fluid levels
- Submucosal haemorrhage and oedema- Wall thickening
- Gangrene-Linear gas streaks in bowel wall
- Perforation- free gas
-Gas in the portal vein-grave prognostic sign
‰ CT-
- Bowel wall thickening
- Engorgement of mesenteric veins
- Increased attenuation of mesenteric fat

33. Large bowel obstruction
‰ Common causes include tumour, abscess, diverticular
disease, volvulus etc
‰ Plain radiographs- depends on the site of obstruction and
the competency of the ileo-caecal valve
Type Ia
Type Ib
Type II

34. Large bowel volvulus
• Sigmoid colon and caecum ‐ most common sites
• Compound volvulus, involving interwining of two loops of bowel is rare

35. Caecal volvulus
‰ Seen when caecum & ascending colon
are on a mesentery
‰ the caecum twists and inverts( 50%),
in the other half the twist occurs in
an axial plane
‰ Plain radiograph - large viscus filled
with gas and fluid
- 1 or 2 haustral markings
- left side of the colon
is collapsed

36. Sigmoid volvulus
• Twisting of the sigmoid loop around the mesenteric axis, axial torsion
is rare
• Plain radiograph‐
• northern exposure sign
coffee bean sign
white stripe sign
three line sign

37. Sigmoid volvulus

38. Contrast enema-
-“ bird of prey” sign-smooth,
curved tapering of the
barium column
-mucosal folds show a
“cork screw “ pattern
-In chronic cases-
shouldering
Bird of prey & cork screw app

39. Distinction between
small and
large bowel dilatation
Small bowel Large bowel
Valvulae conniventes present in jejunum Absent
No. of loops Many Few
Distribution of loops Central Peripheral
Haustra Absent Present
Diameter 3-5 cm 5 cm+
Radius of curvature Small Large
Solid faeces Absent Present

40. Paralytic ileus
• Occurs when intestinal
peristalsis ceases and, as a
result, fluid and gas accumulate
in the dilated bowel
• Abdominal radiographs‐
‐small and large
bowel dilatation
‐ multiple fluid levels

41. Acute Colitis

42. Toxic megacolon
‰ A fulminating form of colitis with
trans-mural inflammation,
extensive and deep ulceration and
neuromuscular degeneration
‰ Plain abdominal radiographs-
- mucosal islands
- dilatation(>5.5cm)
-perforation : pneumoperitoneum

43. Ischaemic colitis
‰ Disorder caused by vascular insufficiency
and bleeding into the wall of the colon
‰ Preferentially involves the splenic flexure
‰ Ischaemia causes oedema, haemorrhage &
ulceration and fibrosis following
transmural ischaemia may result in
stricture formation
‰ Imaging- splenic flexure irregularity with
mural thickening
Barium studies :
-Thumb printing
- ulcerations
- loss of haustra Thumb printing

44. Inflammatory conditions

45. Acute appendicitis
o Commonest acute surgical condition in the developed world
o Radiological signs-
ƒ Appendix calculus(0.5-0.6)cm
ƒ Right lower quadrant mass indenting
the caecum
ƒ Dilated caecum
ƒ Sentinel loop
ƒ Widening / blurring extraperitoneal
fat line
ƒ Scoliosis concave to the right
ƒ Right lower quadrant haze
ƒ Gas in the appendix

46. ‰ Ultrasonography:
ƒ Blind ending tubular structure
ƒ Non compressible
ƒ Diameter 7 mm or greater
ƒ No peristalsis
ƒ Appendiculolith
ƒ High echogenicity non-compressible
surrounding fat
ƒ Surrounding fluid or abscess

47. ‰ Barium study:
- mass indenting the caecum
- displacement of caecum
- partial filling or non filling of the appendix

48. ‰ C.T. :
- Appendix measuring greater than 6mm in diameter
- Failure of the appendix to fill with oral contrast / air upto its tip
- Appendiculolith
- Wall enhancement
- The ‘arrow head’ sign

49. Acute cholecystitis
Almost all cases of acute cholecystitis are associated with gall
stones and most are caused by obstruction of the cystic duct
Plain radiograph- normal in 2/3rd cases
o Gall stones
o Porcelein GB
o Distended GB
o Duodenal ileus
o Hepatic flexure ileus
o Gas within the gallbladder or biliary tree

50. Ultrasound-
- Mural thickening >3mm, with a hypoechoic halo
- Pericholecystic abscess formation
- Gallstones/ sludge
- Positive sonographic Murphy’s sign

51. Acute pancreatitis
Inflammation of the pancreas with release of various enzymes
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

52. Bone changes-
o Bone infarcts
o Avasular necrosis
o Lytic lesions
CT-
o Demonstrates gland enlargement, necrosis, haemorrhage and presence of
solid parenchyma
o Localisation of extrapancreatic fluid collection
o Detect pseudocyst formation
Balthazar et.al. devised the following grading system based on CT findings-
Grade A : Normal pancreas
Grade B : focal or diffuse enlargement of the gland
Grade C : peripancreatic oedema and intrinsic abnormalities of grade A
Grade D : single, ill-defined fluid collection or phlegmon
Grade E : two or more fluid collections or presence of gas
USG-
o Pancreatic enlargement,
hypoechoic parenchyma
o Fluid collections
o Ascitis

56. Intra‐abdominal abscess
‰ Abscesses are collections of pus that may displace adjacent structures
following their involvement by inflammatory process

57. Subphrenic abscess
• Nearly always occurs as a result of surgery
• Chest X‐ray‐ raised hemidiaphragm
‐ basal consolidation
‐ pleural effusion
‰ Abdominal radiographs‐ gas/fluid level
‐ Irregular gas pocket
‐ Scoliosis towards the lesion
‐ localised paralytic ileus
‰ Fluoroscopy‐ decrease diaphragmatic movement
‐ locates small gas‐fluid level/ irregular gas pockets

58. ƒ Barium studies- displacement of bowel
- Presence of gas/fluid level outside the bowel
ƒ USG- helpful in detection of gas free abscesses
ƒ CT- ill defined or partially encapsulated fluid collections
with/ without gas foci
ƒ Radionuclide scanning – Indium-111 chelated to leucocytes with
either oxine or tropolone

59. Sub-phrenic abscess

60. Trauma

61. Visceral injuries
Pattern of injuries encountered at laparotomy following trauma
Organ Relative incidence
(i) Spleen 46%
(ii) Liver 33%
(iii) Mesentery 10%
(iv) Urologic 09%
(v) Pancreas 09%
(vi) Small bowel 08%
(vii) Colon 07%
(viii) Duodenum 05%
(ix) Vascular 04%
(x) Gall bladdder 02%

62. Splenic trauma
• Most commonly injured organ
• Lesions may be‐
‐ subcapsular/intrasplenic haematomas
‐ splenic lacerations
• USG‐ normal appearing spleen with
free intraperitoneal fluid
‐ curved/cresenteric subcapsular
haematoma
‐ round, linear or irregular
intrasplenic haematomas
‐ non‐homogenous splenic
echotexture
Lacerated splenic injury

63. Splenic laceration Fractured spleen
CT- modality of choice
o Subcapsular haematomas- low attenuation collections that
indent the splenic margin
o Intrasplenic haematoma- diffuse hypoattenuating lesions
o Splenic lacerations- low attenuation defects
o Complex interconnecting lacerations- shattered spleen
Angiography- determines presence of active extravasation

64. Benya’s grading of splenic injury(1995)
Grade I- superficial laceration & subcapsular haematoma
(<1cm in diameter)
Grade II- parenchymal laceration/central/subcapsular
haematoma (<3cm in diameter)
Grade III- lacerations/central or subcapsular
haematoma(>3cm)
Grade IV- three or more lacerations(>3 cm deep)
or foci of devascularized spleen

65. Hepatic trauma
• 2nd most injured organ in blunt
abdominal trauma
• Right lobe> left lobe
ƒ USG:
o haematomas‐
:subcapsular( lens shaped)
:deep (linear, spherical, ovoid,
irregular or branching)
o Bilomas‐ anechoic well defined
intra/extrahepatic masses
without any visible capsule Hepatic laceration

66. CT: contrast enhanced CT remains the best investigative modality
Contusions- illdefined areas of low attenuation
Lacerations- low attenuation areas in linear or branching patterns
- multiple radiating lacerations-“bear claw” appearance
Haematomas –subcapsular: indents the liver margin
- intraparenchymal: round/oval with central high
attenuation
Fractures- laceration extending from one surface to another

67. Bear claw appearance
Subcapsular haematoma

68. CT grading (blunt abdominal trauma):
Grade I-capsular avulsion, superficial lacerations(<1cm deep),
subcapsular haematoma(<1cm thick),
isolated periportal blood tracking
Grade II-Parenchymal laceration(s)1-3 cm deep,
central/subcapsular haematoma(s) 1-3 cm
Grade III- laceration(s) >3 cm deep,
central/subcapsular haematoma(s) >3 cm
Grade IV- massive central/subcapsular haematoma >10 cm,
lobar tissue destruction or devascularisation
Grade V- Bilobar tissue destruction or devascularisation

69. Gall bladder & extrahepatic
biliary tree
trauma
‰ Very rare
USG CT
Perforation pericholecystic fluid ascitis
collapsed GB localised fluid collection
ascites collapsed GB
Contusion wall thickening wall thickening with
of GB inhomogenous enhancement
Avulsion biloma biloma
hemoperitoneum hemoperitoneum

70. GB haematoma

71. Renal injury
• Occurs in 8‐10% of all abdominal trauma
• Predisposing factors‐ anatomical variants like horse shoe,
cross fused and pelvic or transplanted
kidney
• IVU – confirm the presence of a functioning kidney on the
contralateral side
• USG‐ acute retroperitoneal or renal haematoma appears
hypoechoic, becoming more hyperechoic with time

72. CT is the gold standard in renal trauma with accuracy as high as 98%
Contusions- ill-defined areas of low attenuation with irregular margins
Traumatic segmental infarcts- well defined and wedge shaped
Lacerations- linear disruption that may extend into the medulla,
causing urinary extravasation
Intra renal haematoma- expand the kidney
Subcapsular haematoma- distort the renal contour
Angiography: to investigate delayed or protracted bleeding
: treatment of CT detected traumatic vascular
malformations

74. Classification of renal trauma according to severity
(Federle’s classification):
Category I(75-85%)-contusions and CM lacerations that donot
communicate with the collecting system
Category II(10-15%)-parenchymal lacerations communicating with the
collecting system resulting in extravasation
-perinephric/paranephric haematoma
Category III(5%) -major renal lesions or damage to vascular pedicle
-renal arterial avulsion/thrombosis
-multiple fractures running across segmental blood vessels
-Rarely, traumatic renal vein thrombosis
-subcapsular rim sign-complete renal artery occlusion
Category IV-ureteropelvic junction avulsion
- laceration of renal pelvis
-ureter may fail to fill but calyces are intact

75. Urinary Bladder trauma
• Susceptibility to trauma‐infant bladder
‐ distended/obstructed bladder
• Usually associated with pubic ramus fracture
• Classification‐
o Extra‐peritoneal rupture‐ localised collection of contrast lying
anterior & lateral to the bladder
o Intra‐peritoneal rupture‐ splillage of contrast around pelvic small
bowel loops and in the paracolic gutters
o Combined intra & Extraperitoneal rupture
Type I‐ bladder contusion
Type II‐ intra‐peritoneal rupture
Type III‐ interstitial bladder injury
Type IV‐ extra‐peritoneal rupture
Type V‐ combined bladder injury

77. Pancreatic injuries
• Accounts for 3‐12% of cases
• USG ‐diffuse swelling of the pancreas
‐ fluid collections
• CT‐ normal (40%)
‐ thickening of left anterior renal fascia
‐ lacerations & contusions seen as areas of low attenuation
‐ sequele like pseudocyst, abscess detected
• ERCP & MRCP‐ detects site of pancreatic duct rupture
• Angiography‐ detects sites of active bleeding/pseudoaneurysm

79. CT grading (blunt pancreatic injury):
Grade I- minor contusion or laceration without duct injury
Grade II- minor contusion or laceration without duct injury or tissue loss
Grade III- distal transection or parenchymal injury with duct injury
Grade IV- proximal transection or parenchymal injury involving ampulla
Grade V- massive disruption of pancreatic head

80. Bowel and mesentery
• Occurs in 5% of blunt abdominal trauma cases
• Deceleration injuries occurs at
the point of fixation of the bowel
• CT findings‐
‐ oral contrast extravasation
‐ visualisation of the disrupted bowel
‐ extraluminal mesenteric gas
‐ pneumoperitoneum
‐ focal wall thickening
‐ abnormal bowel wall enancement
‐ free peritoneal fluid

81. Vascular injuries
• Very rare except at the junction of the hepatic vein & IVC
• Imaging plays little role
• In haemodynamically stable patients, CT, DSA, doppler studies can be done
• CT‐
o Caval injuries‐ lumen is irregular or compressed by haematoma
‐ active vascular contrast extravasation
o Aortic injuries
‐ contrast extravasation
‐ Psoas or mesenteric haemorrhages
‐ Enhancing pseudoaneurysm
ƒ Angiography‐ gold standard