IMAGING IN ACUTE PANCREATITIS

 

Overview

In this session, we will explore imaging techniques used in acute pancreatitis, including diagnosis, phases of the disease, and key radiographic signs.

Causes of Acute Pancreatitis

• Common Causes:
• Alcohol intake
• Gallstone disease

• Uncommon Causes:
  • Trauma
  • Drugs
  • Post-ERCP complications
  • Tumors
  • Infections (e.g., mumps)

Diagnosis Criteria

Acute pancreatitis is diagnosed when any two of the following criteria are met:

1. Symptoms of epigastric pain radiating to the back.
2. Elevated amylase and lipase levels (more than three times the normal).
3. Typical imaging features present on ultrasound, CT, or MRI.

Phases of Acute Pancreatitis

1. Early Phase (first week):
   • Possible systemic inflammatory response syndrome (SIRS) or multi-organ failure.
2. Late Phase (after the first week):
   • May develop complications like infections or sepsis.

Severity Grading

• Mild: No organ failure or complications.
• Moderate: Transient organ failure (< 48 hours) or local/systemic complications.
• Severe: Persistent organ failure (> 48 hours), with or without complications.

Revised Atlanta Classification

• Acute Interstitial Edematous Pancreatitis:
  • Less than four weeks: peripancreatic collection.
  • More than four weeks: pseudocyst.
• Acute Necrotizing Pancreatitis:
• Less than four weeks: acute necrotic collection.
• More than four weeks: wall of necrosis.

Key Radiographic Signs

• Colon Cutoff Sign: Lack of visualization of the colon due to spasm.
• Sentinel Loop Sign: Localized ileus of a small intestinal loop, typically in the jejunum.

• Emphysematous Pancreatitis: Presence of air foci in the upper abdomen due to anaerobic infections.

• Pleural Effusion: More commonly on the left side; can lead to basal atelectasis.

Imaging Modalities

Ultrasound

• First-line modality to visualize gallstones and assess pancreatic size and echogenicity.
• Bulky, edematous pancreas appears hypoechoic.

CT Imaging

• Timing: Best performed 72 hours after onset for optimal visualization of necrosis.
• Phases:
• Arterial Phase: Visualizes vascular complications.
• Pancreatic Parenchymal Phase: Homogeneous enhancement of pancreatic parenchyma.
• Portal Venous Phase: Visualizes portal vein thrombosis.

Normal Pancreas Appearance on CT

• Positioned anterior to the portal vein.
• Size criteria:
  • Head: 23 ± 3 mm
  • Neck: 19 ± 2.5 mm
  • Body: 20 ± 3 mm
  • Tail: 15 ± 2.5 mm

MRI Appearance

• Slightly hyperintense on T1-weighted images compared to liver and spleen.

Pathologies

Acute Interstitial Pancreatitis

• Bulky, edematous pancreas with surrounding fluid collections.
• Differentiates into peripancreatic collections or pseudocysts based on time.

Acute Necrotizing Pancreatitis

• Necrotic collections appear hypodense and heterogeneous within the pancreatic parenchyma.
• After four weeks, this becomes a wall of necrosis.

Pseudocyst

• Thick-walled, homogeneously appearing cystic lesions.

Complications

• Vascular Complications: Arterial pseudoaneurysm or rupture, venous thrombosis.
• Infected Necrosis: Can occur due to collections.
• Bowel Complications: Necrosis or perforation.
• Pancreatic Ascites: Accumulation of fluid.

Conclusion

Imaging plays a crucial role in diagnosing and managing acute pancreatitis. Understanding the various stages, complications, and imaging characteristics helps guide appropriate treatment.

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