CT Imaging of Acute Pancreatitis

Erin Rikard

Radiology

December 2007

Outline

• Definition• Epidemiology• Causal Factors• Pathophysiology• CT Evaluation and Findings – Normal and

abnormal• Complications• Management• Prognosis

Definition

Definition

Acute Pancreatitis -

Inflammation of

pancreas with

potential for

complete healing

Epidemiology

Epidemiology

• 79.8/100,000 per year → 185,000 new cases annually in U.S.

• Peak incidence in 6th decade

Causal Factors

Causal Factors

Etiology Incidence

Cholelithiasis 30-60%

Alcohol 15-30%

Iatrogenic 2-5%

Trauma/Surgery --

Metabolic Disorders --

Viral Infection --

Pathophysiology

Pathophysiology

• Pancreatic autodigestion, with activated pancreatic enzymes escaping the ductal system and lysing tissue of pancreas and adjacent structures

• Lack of capsule facilitates spread

Normal CT Findings

Normal Anatomy by CT

• Pancreas arcing anteriorly over spine

• Head adjacent to duodenum

• Tail extending toward spleen

• Splenic vein posterior to body and tail

• Portal vein confluence immediately posterior & left of pancreatic neck

Normal Morphology by CT

• Pancreatic acini → lobulated contour• 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) Empties into ampulla of Vater, along medial aspect

of 2nd portion of duodenum

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CT scans of normal kidneys and pancreas

Spleen

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Pancreas

Evaluation by CT

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

Recommendations for Contrast-Enhanced CT

• Clinical diagnosis in doubt

• Severe clinical pancreatitis

• Ranson score > 3

• APACHE score > 8

• Failure to rapidly improve within 72 hours of beginning conservative medical therapy

• Initial improvement with later deterioration

Ranson Criteria

At admission

• Age > 55• WBC > 16,000• Blood glucose > 200• Serum AST > 250• Serum LDH > 350

After 48 hours

• Hematocrit ↓ > 10%• ↑ BUN ≥ 1.8 after

rehydration• Serum calcium < 8.0• PO2 < 60• Base deficit > 4 • Estimated fluid

sequestration > 6L

Abnormal CT Findings

• Peripancreatic inflammation

• Diffuse or focal pancreatic edema

• Poor definition and heterogeneity of gland

• Fluid collections

• Necrosis

• Thickening of pararenal fascia

Abnormal CT Findings

Spectrum of Disease

• Mild Cases May be normal or

show only mild gland enlargement

• Severe Cases May reveal

peripancreatic fluid &/or pancreatic necrosis and phlegmon

Peripancreatic Inflammation/ Pancreatic Edema/

Fluid Collections

Transverse CT scan obtained with intravenous and oral contrast material reveals a large, edematous, homogeneously attenuating (73-HU) pancreas (1) and peripancreatic inflammatory changes (white arrows). Although the attenuation values are low, there is no pancreatic necrosis. Calcified gallstones are seen in gallbladder (black arrow). 2 = liver (140 HU).

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Infection?• Gallium-67 SPECT (perfusion studies)

• ? with (+) findings had infection at intervention – 78% of all patients

• No false (+)

• No correlation between gallium uptake and presence or absence of necrosis

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47-year-old man with severe pancreatitis

Fluid collection replacing pancreatic body and tail

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647-year-old man with severe pancreatitis

47-year-old man with severe pancreatitis who had true-positive finding for 47-year-old man with severe pancreatitis who had true-positive finding for infection on gallium study. Fusion image of CT scan and gallium study was infection on gallium study. Fusion image of CT scan and gallium study was helpful in localizing infection. helpful in localizing infection.

Necrosis

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57-year-old man with acute necrotizing pancreatitis and severe back pain

Large region of unenhancement (necrosis) involving most of body and tail of pancreas. Inflammatory fluid is present in anterior pararenal space. Note ascites around liver.

50 year-old woman with acute pancreatitis (1st view)

(a, b) Transverse CT scans obtained with intravenous and oral contrast material reveal an encapsulated fluid collection associated with liquefied necrosis (large straight arrows) in the body of the pancreas. The head, part of the body, and the tail of the pancreas are still enhancing (small straight arrows). N = liquefied gland necrosis, S = stomach.

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(a, b) Transverse CT scans obtained with intravenous and oral contrast material. The head, part of the body, and the tail of the pancreas are still enhancing (straight arrows). Residual fluid collections and areas of soft-tissue attenuation (curved arrow) consistent with fat necrosis are seen adjacent to the pancreas. f = fluid, N = liquefied gland necrosis.

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Complications

Complications

• Pancreatic Pseudocysts

• Abscess

• Hemorrhagic Pancreatitis

• Splenic Artery Pseudoaneurysm formation or rupture/ Splenic Venous Thrombosis

Pancreatic Pseudocyst

• Fluid collection surrounded by fibrous capsule but not lined by epithelium

• Occurs in 10% of cases

• Significant % will not resolve spontaneously

• Seen within pancreas and potential spaces with which gland is continuous (lesser sac and left pararenal space)

28 year-old man with pseudocyst

Image demonstrates a pseudocyst (arrow) in the tail of the pancreas surrounded by a thick enhancing wall. The lesion appears heterogeneous with central areas of higher attenuation, which is suggestive of fresh hemorrhage. Note infiltration (arrowheads) of the peripancreatic fat.

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Axial CT scan obtained with intravenous contrast material demonstrates calcifications from chronic pancreatitis in the head of the pancreas. A high-attenuation focus of blood (arrow) is seen within the low-attenuation pseudocyst, a finding that is consistent with hemorrhage.

44 year-old man with acute abdominal pain – hemorrhagic pseudocyst

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Abscess

• 1 in 20 cases and fatal in ¾ of cases

• Suspected clinically with fever and septicemia

• Pathognomonic finding → presence of gas bubbles in pancreatic bed

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Pancreatic abscess containing gas in 54-year-old man

Large fluid collection containing gas bubbles in pancreatic bed due to abscess complicating acute pancreatitis. Note infiltration of peripancreatic fat and calcified gallstones.

Hemorrhagic Pancreatitis

• Rare• Noted clinically by ↓ in

hematocrit

CT scan demonstrates hemorrhagic pancreatitis as a heterogeneous mass in the area of the pancreatic bed (*). Arrow indicates active extravasation (hemorrhage).

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Splenic Artery Pseudoaneurysm

• Presents similarly to hemorrhagic pancreatitis with a ↓ in hematocrit

Axial CT scan with intravenous contrast material reveals a pseudoaneurysm (arrow) projecting from the splenic artery.

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Management

Management

• Acute pancreatitis usually self-limited Inflammation ↓ within 3-7 days in 90% of

cases

• Medical therapy Analgesics IV hydration Decrease PO intake → Decreased pancreatic

secretionAntimicrobials in severe necrotizing

pancreatitis

• Presence of abscess or necrosis indicates need for intervention

• Percutaneous drainage of abscess

• Surgical debridement (necrosectomy) of infected necrotic tissue when conservative treatment has failed

Management

Prognosis

Prognosis

• Mortality ↓ over last 20 years 5% for all cases20% for severe cases

Reasons for Reduced Mortality• Initially - Recognition and application of

severity signs• 1990s – More selective endoscopic or

surgical debridement of infected tissue, endoscopic cyst drainage, and angiographic control of GI bleeding

• Later – Improved nutritional support by jejunal feeding, earlier use of antibiotic therapy, gut sterilization, early ERCP for common bile duct stones, and necrosectomy for necrotic tissue

Resources

Resources• Balthazar, Emil J. “Acute Pancreatitis: Assessment of Severity With

Clinical and CT Evaluation.” Radiology. 2002; 223: 603-613.• Banu, S., P. Singh, N. Pooran, and B. Stark. “Evaluation of Factors

That Have Reduced Mortality from Acute Pancreatitis Over the Past 20 Years.” Journal of Clinical Gastroenterology. 2002 July; 35: 50-60.

• Bennett, William F., Kuldeep Vaswani, and Kenneth Vitellas. “Case 1: Parenchymal Lymphoma.” American Journal of Roentgenology. 2000; 175: 882-883.

• Cohen-Scali, Frank, et al. “Discrimination of Unilocular Macrocystic Serous Cystadeoma from Pancreatic Pseudocyst and Mucinous Cystadenoma with CT: Initial Observations.” Radiology. 2003; 228: 727-733.

• Demos, Terrence C., et al. “Cystic Lesions of the Pancreas.” American Journal of Roentgenology. 2002; 179: 1375-1388.

• Gore, Richard M., et al. “ Helical CT in the Evaluation of the Acute Abdomen.” American Journal of Roentgenology. 2000; 174: 901-913.

Resources Continued• Gunderman, Richard B. Essential Radiology. 1998.• Greenberger, Norton J. and Phillip P. Toskes. “Acute and Chronic

Pancreatitis.” Harrison’s Internal Medicine. • Mitchell, RM, MF Byrne, and J. Baillie. “Pancreatitis.” Lancet. 2003

Apr 26; 361: 1447-1455.• Novelline, Robert A. Squire’s Fundamentals of Radiology. 6th ed.

2004.• Pretorius, E. Scott and Jeffrey A. Solomon. Radiology Secrets. 2nd

ed. 2006. • Ranson, JH, et al. “Prognostic Signs and the Role of Operative

Management in Acute Pancreatitis.” Surgery, Gynecology, and Obstetrics.

• Tang, Linda J., Stan Zipser, and Young S. Kang. “Temporary Spontaneous Thrombosis of a Splenic Artery Pseudoaneurysm in Chronic Pancreatitis During Intravenous Octreotide Administration.” Journal of Vascular Interventional Radiology. 2005; 16: 863-866.

Resources Continued• Urban, Bruce A. and Elliot K. Fishman. “Tailored Helical CT

Evaluation of Acute Abdomen.” Radiographics. 2000; 20: 725-749.• West, Jeffrey H., Stephen B. Vogel, and Walter E. Drane. “Gallium

Uptake in Complicated Pancreatitis.” American Journal of Roentgenology. 2002; 178: 841-846.