This document discusses imaging of the pancreas using CT. It provides details on the CT pancreas protocol, including indications, purposes, techniques, and assessment of acute pancreatitis. Key points include: 1) CT is used to confirm acute pancreatitis diagnosis and differentiate interstitial from necrotizing pancreatitis. 2) Necrosis is best assessed on contrast-enhanced CT. 3) Fluid collections are classified based on age and presence of capsule wall. CT severity index sums Balthazar score and necrosis extent to assess severity.

1. Imaging of Pancreas
Dr. Shireen Ahmed
Assistant professor
Dept. of GHPD

2. CT pancreas protocol
The CT pancreas protocol serves as an outline
for a dedicated examination of the pancreas. As a
separate examination, it is usually conducted
as a biphasic contrast study and might be
conducted as a part of other scans such as CT
abdomen-pelvis, CT chest-abdomen-pelvis.

3. Indications
Typical indications include an evaluation of the
following:
• jaundice
• evaluation of pancreatic tumors and/or cystic
lesions
• acute or chronic pancreatitis
• complications of pancreatic diseases
• unclear findings on ultrasound or CT abdomen
• pancreatic interventions (e.g. CT-guided
biopsy, drainage)

4. Purpose
• The purposes of a pancreatic CT includes the
following :
• detection and characterization of pancreatic tumors
– arterial phase: hypervascular
lesions e.g. neuroendocrine tumors, vascular lesions
– pancreatic phase: depiction of hypoattenuating
tumors such as pancreatic ductal adenocarcinoma
– portal venous phase: depiction of hepatic
metastases, venous thrombosis etc.
• detection and characterization of cystic pancreatic
lesions

5. • acute pancreatitis
– staging and severity assessment (best-done ≥2-
3days after symptom onset)
– search for etiology
(choledocholithiasis, autoimmune
pancreatitis, etc.)
– detection of complications in early and late
phases including extrapancreatic complications
– confirmation of the diagnosis of pancreatitis (only
if clinically unclear - rare)
• chronic pancreatitis
• identification and characterization of pancreatic
calcifications
Purpose

6. Technique
• patient position
– supine position, abdomen centered within the
gantry
– both arms elevated
• scout
– diaphragm to the iliac crest (or symphysis)
• scan extent
– arterial/pancreatic phase: mid diaphragm to the
iliac crest
– venous phase: above the diaphragm to the iliac
crest, might be extended to include the whole
pelvis
• scan direction- craniocaudal

7. • oral contrast
– neutral contrast agent: 800 ml water 20-30min before
the scan
• contrast injection considerations
– non-contrast (rarely indicated)
– biphasic pancreatic ± venous acquisition (pancreatic
mass)
• contrast volume: 70-120ml (1 mL/kg) with 30-40
mL saline chaser at 3-5 mL/s
• pancreatic phase: scan delay 15-20 sec after
trigger or 35-40 sec after contrast injection
• portal venous phase: 30 sec after the pancreatic
phase or 65-70 sec after contrast injection

8. – biphasic arterial ± venous acquisition (neuroendocrine
tumors)
• contrast volume: 70-120ml (1 mL/kg) with 30-40
mL saline chaser at 4-5 mL/s
• arterial phase: minimal scan delay
• portal venous phase: 40 seconds after the arterial
phase or 60-70 seconds after contrast injection
– single acquisition with a monophasic injection
(venous phase)
• contrast volume: 70-120ml (1 mL/kg) with 30-40
mL saline chaser at 3-5 mL/s
• portal venous phase: 65-70 sec after contrast
injection

9. • respiration phase
– single breath-hold: inspiration
• multiplanar reconstructions
– slice thickness: soft tissue ≤2,5 mm, bone ≤2
mm overlap 20-40%

10. Acute pancreatitis
The role of imaging is manifold:
• to clarify the diagnosis when the clinical picture
is confusing
• to assess severity (e.g. Balthazar score) and
thus to determine prognosis
• to detect complications
• to determine possible causes

11. • Imaging studies of acute pancreatitis may be
normal in mild cases.
• Contrast-enhanced CT provides the most
comprehensive initial assessment, typically with
a dual-phase (arterial and portal venous)
protocol.
• However, ultrasound is useful for the follow-up of
specific abnormalities, such as fluid collections
and pseudocysts.
Radiographic features

12. Plain radiograph
• Radiographs are insensitive for evidence of acute
pancreatitis: many patients have normal exams.
Moreover, none of the signs is specific enough to
establish the diagnosis of pancreatitis.
Abdominal radiographs may demonstrate:
• localized ileus of the small intestine (sentinel loop)
• spasm of the descending colon (colon cut-off sign)
Chest radiographs may demonstrate:
• Pleural effusion, usually left-sided
• Hemi-diaphragm elevation
• Basal atelectasis
• pulmonary edema suggestive of acute respiratory
distress syndrome

13. Sentinel loop
• A sentinel
loop is a short
segment
of adynamic
ileus close to an
intra-abdominal
inflammatory
process.

14. Colon cut-off sign
The colon cut-off sign describes gaseous
distension seen in the proximal colon associated
with abrupt termination of gas within the colon
usually at the level of the splenic flexure and
decompression of the more distal part of the colon.

16. Ultrasound
The main role of ultrasound is:
• to identify gallstones as a possible cause
• diagnosis of vascular complications, e.g.
thrombosis
• identify areas of necrosis that appear as
hypoechoic regions
• assessment of clinically similar etiologies of an
acute abdomen

17. • Typical ultrasonographic features with acute
pancreatitis include:
increased pancreatic volume with a marked decrease
in echogenicity
– volume increase quantified as a pancreatic body
exceeding 2.4 cm in diameter, with marked
anterior bowing and surface irregularity
– decreased echogenicity secondary to fluid
exudation, which may result in a marked
heterogeneity of the parenchyma
• displacement of the adjacent transverse colon
and/or stomach secondary to pancreatic volume
expansion
Ultrasound

18. Complications
• Pancreatic fluid collections are defined by presence or absence of
necrosis (as described by the Revised Atlanta Classification):
– necrosis absent (i.e. interstitial edematous pancreatitis)
• acute peripancreatic fluid collections (APFCs) (in the first 4
weeks)
• pseudocysts: encapsulated fluid collections after 4 weeks
– necrosis present (i.e. necrotizing pancreatitis)
• acute necrotic collections (ANCs): develop in the first 4
weeks
• walled-off necrosis (WON): encapsulated collections after 4
weeks
• Liquefactive necrosis of pancreatic parenchyma (e.g. necrotizing
pancreatitis)
– increased morbidity and mortality
– may become secondarily infected (emphysematous
pancreatitis)

19. • Vascular complications
– hemorrhage: resulting from erosion of blood
vessels and tissue necrosis
– pseudoaneurysm: autodigestion of arterial walls
by pancreatic enzymes results in pulsatile mass
that is lined by fibrous tissue and maintains
communication with parent artery
– splenic vein thrombosis
– portal vein thrombosis
• Fistula formation with pancreatic ascites: leakage of
pancreatic secretions into the peritoneal cavity
• Abdominal compartment syndrome
Complications

20. • Abdominal compartment syndrome (ACS) is
a severe illness seen in critically ill
patients. ACS results from the progression
of steady-state pressure within the
abdominal cavity to a repeated pathological
elevation of pressure above 20mmHg with
associated organ dysfunction.

21. MRI
• Contrast-enhanced MRI is equivalent to CT in
the assessment of pancreatitis.

22. CT severity index (CTSI)
• The CT severity index (CTSI) is based on
findings from an enhanced CT scan to assess
the severity of acute pancreatitis. The severity
of acute pancreatitis CT findings has been found
to correlate well with clinical indices of severity.
• The CT severity index sums two scores:
• Balthazar score: grading of pancreatitis (A-E)
• grading the extent of pancreatic necrosis
• The necrosis scoring system was added to the
traditional Balthazar score in 1990
• Modifications have been made to the CTSI,
resulting in the modified CTSI (2004).

23. CT severity index
Grading of pancreatitis (Balthazar score)
• A: normal pancreas: 0
• B: enlargement of pancreas: 1
• C: inflammatory changes in pancreas and
peripancreatic fat: 2
• D: ill-defined single peripancreatic fluid collection: 3
• E: two or more poorly defined peripancreatic fluid
collections: 4
Pancreatic necrosis
• none: 0
• ≤30%: 2
• >30-50%: 4
• >50%: 6

24. Balthazar score

25. CT severity index
The CT severity index is the sum of the scores
obtained with the Balthazar score and those
obtained with the evaluation of pancreatic
necrosis:
• 0-3: mild acute pancreatitis
• 4-6: moderate acute pancreatitis
• 7-10: severe acute pancreatitis

27. Peripancreatic fluid collection

28. Pancreatic pseudocyst

29. Necrotizing pancreatitis

30. Walled-off pancreatic necrosis

31. KEY POINTS
1. CT is used to confirm the diagnosis of acute
pancreatitis when the diagnosis is in doubt and to
differentiate acute interstitial pancreatitis from
necrotizing pancreatitis, which is a key element of
the updated Atlanta nomenclature. The acute
interstitial variety accounts for 90–95% of cases,
with acute necrotizing pancreatitis accounting for
the remaining cases.

32. 2. Necrosis due to acute pancreatitis is best
assessed on IV contrast-enhanced CT performed
40 seconds after injection. Peripancreatic necrosis
is a subtype of necrotizing pancreatitis in which
tissue death occurs in peripancreatic tissues. This
is seen in isolation in 20% of patients with
necrotizing pancreatitis.
KEY POINTS

33. 3. Simple fluid collections associated with acute
interstitial pancreatitis are subdivided
chronologically. A collection observed within
approximately 4 weeks of acute pancreatitis onset is
termed an “acute peripancreatic fluid collection
(APFC).” A collection older than 4 weeks should
have a thin wall and is termed a “pseudocyst.” Both
APFCs and pseudocysts can be infected or sterile.
KEY POINTS

34. 4. Fluid collections associated with necrotizing
pancreatitis are labeled on the basis of age and the
presence of a capsule. Within 4 weeks of acute
pancreatitis onset, a fluid collection associated with
necrotizing pancreatitis is termed an “acute necrotic
collection (ANC)” whereas an older collection is
termed an area of “walled-off necrosis (WON)” if it
has a perceptible wall on CT. The term “pseudocyst”
is not used in the setting of necrotizing pancreatitis
collections. Although an ANC and a (WON can be
infected or sterile, infection is far more likely
compared with acute interstitial pancreatitis
collections.
KEY POINTS

35. 5. The severity of acute pancreatitis is graded on the
basis of the presence of acute complications or organ
failure. Mild acute pancreatitis has neither acute
complications nor organ failure. Moderate-severity
acute pancreatitis is associated with acute
complications or organ failure lasting fewer than 48
hours. Severe acute pancreatitis is characterized by
single- or multiorgan failure persisting for greater than
48 hours
KEY POINTS