Role of CT in acute pancreatitis

Consultant radiologist Riyadh Military Hospital

Dr. Ahmed Refaey

Normal CT anatomy of the upper abdomen

Anterior pararenal space

Normal Anatomy by CT• Pancreas is located in the

anterior pararenal space• Head adjacent to

duodenum• Tail extending toward

spleen• Splenic vein posterior to

body and tail

Normal Morphology by CT

• No capsule• AP dimensions

Head 2-2.5 cm Body and tail 1-2 cm

• Pancreatic duct Maximal diameter 3 mm in adults (5 mm in elderly)

Evaluation of Acute Pancreatitis

• Contrast-enhanced CT is imaging modality of choice

• Oral and IV contrast differentiate pancreatic tissue from adjacent blood vessels and duodenum

• There is no additional value of an early CT (within 72 hours) in patients with acute pancreatitis.

• The diagnosis is usually made on clinical and laboratory findings.

• An early CT may be misleading concerning the severity of the pancreatitis, since it can underestimate the presence and amount of necrosis.

Etiology

Pathophysiology

• Activated pancreatic enzymes escaping the ductal system and auto digesting the pancreas and adjacent structures ( mainly amylase, lipase & trypsin ).

• Lack of capsule facilitates spread

Acute pancreatitis

• Mild acute pancreatitis ----- 80 % * edematous ( interstitial ) * exudative

• Severe acute pancreatitis ----20 %

• Mild acute pancreatitis

- run a mild course without development of multiple organ failure

- improvement within 3 days following conservative therapy with gradual decrease of elevated enzymes.

- has a mortality rate of < 1%

• Severe acute pancreatitis “ necrotizing “

- run a serious clinical course with pancreatic necrosis and the development of multiple organ failure

- of these, 60% of pancreatic necrosis remain sterile , while 40% becomes infected

- this last category ( infected necrosis ) , has the highest mortality rate ( 25-70%)

Clinical outcome

CT Imaging of acute pancreatitis

• Acute edematous “interstitial” pancreatitis• Acute exudative pancreatitis

Mild acute pancreatitis

Acute edematous “interstitial” pancreatitis

• Edematous pancreas with/without peripancreatic

fat stranding.• No collections or necrosis

Acute exudative pancreatitis

• an intermediate form of pancreatitis without pancreatic necrosis with an intermediate clinical course.

• This is called extrapancreatic necrosis (EXPN)

• Avoid early drainage of collections and avoid introducing infection!

• 50% of these collections show spontaneous regression The other 50% either remain stable ( pseudocyt ) or develop infection ( abscess ) .

Peripancreatic fluid

50% spontaneous regression 50% stable

sterile ( pseudocyst) infection ( asbscess )

Spontaneous regression of peripancreatic collection

Severe pancreatitis “ necrotizing pancreatitis”

occurs in 20% of patients.

* partial necrotizing pancreatitis * total necrotizing pancreatitis

Partial necrotizing Total necrotizing

• Delayed or no response to conservative therapy

• Delayed or no normalization of enzymes

• Mortality : 30 – 75 %

• Deterioration under conservative therapy

• Mortality : 100 % - 40% by 2nd day - 75% by 5th day - 100% by 10th day

Central gland necrosis

Central gland necrosis

• Subtype of necrotizing pancreatitis.• Necrosis between the pancreatic head and tail and is

nearly always associated with disruption of the pancreatic duct.

• This leads to persistent collections as the viable pancreatic tail continues to secrete pancreatic juices.

• These collections react poorly to endoscopic or percutaneous drainage.

• Definitive treatment often requires distal pancreatectomy.

• An early CT may be misleading concerning the severity of the pancreatitis, since it can underestimate the presence and amount of necrosis.

Mortality

• Early mortality in acute pancreatitis is the result of the systemic inflammatory response with multiple organ failure.

Late mortality is the result of infection of pancreatic necrosis and peripancreatic fluid collections which results in sepsis and is seen in more than 50% of deaths.

• CT Severity Index

• It is critical to identify patients who are at high risk for severe disease, since they require close monitoring and possible intervention

• Balthazar et al constructed a CT severity index (CTSI) for acute pancreatitis that combines the grade of pancreatitis (A-E) with the extent of pancreatic necrosis.

CT Severity Index

• 1- 3 …………….. Mild • 4-6 …………….. Moderate • 7-10 ……………. Severe

Complications of pancreatits

Complications

• Pancreatic Pseudocysts• Abscess• Hemorrhagic Pancreatitis• Splenic Artery Pseudoaneurysm

Pancreatic Pseudocyst

• Fluid collection surrounded by fibrous capsule • Time of onset : > 4 weeks from the onset• Amylase rich-fluid• Prognosis : spontaneous resolution in 44%

Abscess

• Well demarcated fluid collection of pus • Suspected clinically with fever and septicemia• Pathognomonic finding → presence of gas• Time of onset : 2- 4 weeks after onset

Hemorrhagic pancreatitis

• Type of severe pancreatitis• Peripancreatic fat necrosis and hemorrhage

due to erosion of small vessels• Falling hematocrit • Cullen sign and Grey-Turner sign

–

• (Grey-Turner sign): flank ecchymosis • (Cullen sign) : periumbilical ecchymosis

• associated with a 37% mortality rate

• Grey Turner sign• Cullen’s sign

Splenic Artery Pseudoaneurysm

• Presents similarly to hemorrhagic pancreatitis with a ↓ in hematocrit

Take home messages

• Severity of acute pancreatitis and pancreatic necrosis can only be reliably assessed by imaging after 72 hours.

• CT can not reliably differentiate between collections that consist of fluid and those that contain solid debris.In these cases MRI can be of additional value.

• Central gland necrosis is a subtype of necrotizing pancreatitis with important implications.

• Avoid early drainage of collections and avoid introducing infection!

Thank you