What is the initial imaging test of choice for diagnosing chronic pancreatitis?

Initial Imaging for Chronic Pancreatitis

CT is the most appropriate initial imaging modality for evaluating suspected chronic pancreatitis, as it depicts most morphological changes, is widely available, and can exclude other intraabdominal pathologies presenting with similar symptoms. 1

Rationale for CT as First-Line Imaging

CT serves as the optimal starting point for several key reasons:

• CT effectively demonstrates advanced disease features including pancreatic calcifications, ductal dilation, gland atrophy, and structural complications that characterize moderate to severe chronic pancreatitis 1, 2
• CT provides rapid, comprehensive abdominal evaluation to exclude alternative diagnoses such as pancreatic malignancy, pseudocysts, or vascular complications that may present with similar symptoms 1, 3
• CT has comparable diagnostic accuracy to other modalities with sensitivity of 75% and specificity of 91% for chronic pancreatitis diagnosis 4

Critical Limitations of CT

Understanding when CT is insufficient is essential for appropriate diagnostic workup:

• CT cannot exclude chronic pancreatitis and has poor sensitivity for early or mild disease where morphological changes are subtle 1
• CT misses early parenchymal and ductal changes that precede calcification and advanced structural abnormalities 1, 3

When to Advance to MRI/MRCP

If CT shows no specific pathological changes but clinical suspicion for chronic pancreatitis remains high, MRI with MRCP is superior and should be performed next. 1

MRI/MRCP offers distinct advantages in this scenario:

• MRI/MRCP has increased sensitivity for pancreatic ductal and gland changes in mild to moderate disease compared to CT 3
• MRI/MRCP demonstrates sensitivity of 78% with specificity of 96% for chronic pancreatitis diagnosis 4
• MRCP is more sensitive and accurate than CT for detecting chronic pancreatitis, as recommended by the American Pancreatic Association 5

Role of Secretin-Enhanced MRCP

For cases where standard MRCP is negative but clinical suspicion persists:

• Secretin-stimulated MRCP is more accurate than standard MRCP for depicting subtle ductal changes and should be performed after negative MRCP when clinical suspicion remains 1
• Secretin-MRCP is not recommended for initial diagnostic investigation due to issues with standardization and interpretation 5

Role of Endoscopic Ultrasound (EUS)

EUS serves as a complementary advanced diagnostic tool:

• EUS detects mild parenchymal and ductal abnormalities not visible on CT with sensitivity of 68-100% and specificity of 78-97% 5
• EUS and MRCP-S are effective diagnostic tests best used in complementary fashion for early/mild chronic pancreatitis when CT or pancreatic function tests are negative or equivocal 5
• EUS has slightly higher sensitivity than MRCP-S for changes suggestive of chronic pancreatitis, though the clinical relevance of some subtle EUS findings remains questionable 5

Common Pitfalls to Avoid

• Do not rely on ultrasound as initial imaging - transabdominal ultrasound has poor sensitivity (approximately 60%) for chronic pancreatitis and the lowest diagnostic accuracy among imaging modalities 5, 4
• Do not assume a negative CT excludes the diagnosis - proceed to MRI/MRCP in patients with persistent clinical suspicion 1
• Do not order invasive pancreatic function tests - these have no place in UK and European practice despite American guidelines recommending them 5