What is the best approach to imaging in a patient with suspected or known chronic pancreatitis?

Imaging in Chronic Pancreatitis

Primary Imaging Recommendation

CT is the most appropriate initial imaging modality for suspected chronic pancreatitis, as it depicts most morphological changes and excludes other intra-abdominal pathologies, but MRI/MRCP is superior for early or mild disease when CT is negative. 1

Initial Imaging Strategy

• Start with contrast-enhanced CT using a dedicated pancreas protocol when chronic pancreatitis is suspected, as it effectively demonstrates calcifications, ductal dilatation, gland atrophy, and pseudocysts in moderate to advanced disease 1, 2

• CT has a sensitivity of 75% (95% CI: 66%-83%) and specificity of 91% (95% CI: 81%-96%) for chronic pancreatitis diagnosis 2

• Critical limitation: CT cannot exclude chronic pancreatitis nor diagnose early/mild disease reliably—a negative CT does not rule out the diagnosis 1

When CT is Negative or Inconclusive

Proceed to MRI/MRCP when clinical suspicion persists despite negative or equivocal CT findings, as MRI is superior for detecting subtle ductal changes and early parenchymal alterations 1, 3

• MRI/MRCP demonstrates sensitivity of 78% (95% CI: 69%-85%) and specificity of 96% (95% CI: 90%-98%), with particular strength in mild to moderate disease 2, 3

• MRI better visualizes pancreatic ductal changes, gland atrophy, and parenchymal fibrosis compared to CT 1, 3

• Secretin-stimulated MRCP should be performed after negative standard MRCP when clinical suspicion remains high, as it is more accurate for detecting subtle ductal changes and can assess exocrine function 1

Role of Endoscopic Ultrasound (EUS)

EUS is an outperformer for diagnosing parenchymal and ductal changes, particularly in early-stage disease, with sensitivity of 81% (95% CI: 70%-89%) and specificity of 90% (95% CI: 82%-95%) 2

• EUS and ERCP have comparable high diagnostic accuracy, with ERCP showing sensitivity of 82% (95% CI: 76%-87%) and specificity of 94% (95% CI: 87%-98%) 2

• The choice between EUS and cross-sectional imaging depends on local availability, expertise, invasiveness considerations, and costs 2

Ultrasound Limitations

Abdominal ultrasound has the lowest diagnostic accuracy with sensitivity of only 67% (95% CI: 53%-78%), though specificity remains high at 98% (95% CI: 89%-100%) 2

• Ultrasound is inadequate as a primary diagnostic tool for chronic pancreatitis and should not be relied upon for definitive diagnosis 2, 4

Diagnostic Algorithm

1. First-line: Contrast-enhanced CT with pancreas protocol to identify moderate-to-advanced disease and exclude alternative diagnoses 1, 2

2. Second-line: MRI/MRCP if CT is negative or equivocal but clinical suspicion persists, especially for early/mild disease 1, 3

3. Third-line: Secretin-stimulated MRCP if standard MRCP is negative but suspicion remains high 1

4. Alternative/Adjunct: EUS when cross-sectional imaging is inconclusive, particularly for early parenchymal changes 2

Key Imaging Features to Assess

• Ductal changes: Main pancreatic duct dilatation, irregularity, strictures, side branch ectasia 1, 4

• Parenchymal calcifications: Best seen on CT, pathognomonic for chronic pancreatitis 1, 3

• Glandular atrophy: Volume loss and size reduction 1

• Parenchymal fibrosis: Better characterized on MRI than CT 1, 3

• Complications: Pseudocysts, vascular thrombosis, bile duct strictures 3

Critical Pitfalls to Avoid

• Do not rely on CT alone to exclude chronic pancreatitis—negative CT does not rule out early or mild disease 1

• Do not use abdominal ultrasound as the primary diagnostic modality—it has insufficient sensitivity for chronic pancreatitis 2

• Do not stop at standard MRCP if negative—secretin-stimulated MRCP significantly improves detection of subtle ductal abnormalities 1

• Recognize that parenchymal changes precede ductal involvement—combining ductal and parenchymal findings improves diagnostic accuracy 3