Acute abdomen causes,role of imaging,modalities and imaging features of a few conditions

1. IMAGING APPROACH IN
ACUTE ABDOMEN
Dr.Parvathy S Nair

2. The 'acute abdomen' is a clinical condition
characterized by severe abdominal pain,
requiring the clinician to make an urgent
therapeutic decision.

3. Role of imaging
• Indicated management may vary from emergency
surgery to reassurance of the patient. So misdiagnosis
may easily result in delayed necessary treatment or
unnecessary surgery.
• 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 symptoms.
• Laboratory findings (leucocyte count, erythrocyte
sedimentation rate, CRP) are equally nonconclusive.

4. CAUSES

5. • Before imaging, clinical history, physical
examination findings, top diagnosis and
possible differentials have to be obtained.
• This helps in choosing the appropriate imaging
modality as well as narrows down the area to
be concentrated

6. Plain Radiographs
• Important initial imaging modality
• Non-specific
• Normal radiograph do not rule out illeus or
other pathology
• Greatest value in cases of hollow viscus
perforation and intestinal obstruction

7. • Abdomen erect including both diaphragm
• Abdomen supine films
• Left lateral decubitus or cross-table lateral
view in ill patients
– Air between the liver and the abdominal wall is
seen easily
• Right lateral decubitus in colonic obstruction

8. Perforation
• RT upper quadrant gas
Perihepatic
Subhepatic
Morrison’s pouch
Ligament visualisation - falciform,umbilical
• Rigler’s sign(double wall sign)
• Triangular air indicating lateral umbilical ligament
• Cupola sign-under surface of the central part of
diaphragm is seen
• Foot ball sign –large quantity of air filling the
peritoneal cavity

10. Cupola sign

12. 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 edemaIschemia
• Intramural air-Necrotizing enterocolitis
• “Coffee bean” appearance- Sigmoid volvulus

14. Appendicitis
• 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.

16. 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

19. USG and CT

20. 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.

21. Appendicitis
• A normal appendix has a maximum diameter of 6
mm, is surrounded by homogeneous noninflamed fat, is compressible and often contains
intraluminal gas.
• An inflamed appendix has a diameter larger than
6 mm, and is usually surrounded by inflamed fat.
The presence of a fecolith or hypervascularity on
power Doppler strongly supports inflammation.

22. Appendicitis

24. 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.

27. Cholecystitis
• As gallstones are often occult on CT,
sonography is the preferred imaging method
for the evaluation of cholecystitis
• GB wall thickening
• Hydropic GB

30. Small Bowel Obstruction
• Small bowel obstruction (SBO) accounts for
approximately 4% of all patients presenting with
an acute abdomen.
• 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.

33. 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.

35. 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.

37. Urolithiasis

38. Ruptured Aneurysm
• Most abdominal aortic aneurysms rupture into the left
retroperitoneum
Clinically this may simulate sigmoid diverticulitis or renal
colic due to impingement of the hematoma on adjacent
structures.
However most patient will present with the classic triad of
hypotension, a pulsating mass and back pain.
Continuous leakage will lead to rupture into the peritoneal
cavity and eventually death.
Sonography is a quick and convenient modality, but it is
much less sensitive and specific for the diagnosis of
aneurysmal rupture than CT.
The absence of sonographic evidence of rupture does not
rule out this entity if clinical suspicion is high.

40. 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

43. 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

44. • 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