Pancreas Divisum

Description

Pancreas divisum is the most common congenital anomaly of the pancreas, resulting from failure of fusion of the dorsal and ventral pancreatic ducts during embryological development. In the normal pancreas, the dorsal duct (of Santorini) and ventral duct (of Wirsung) fuse to form a single main pancreatic duct that drains via the major papilla into the duodenum. In pancreas divisum, the ducts remain separate, and the majority of pancreatic secretions drain through the dorsal duct via the minor papilla.

This configuration may lead to functional obstruction at the minor papilla, particularly during increased exocrine activity, and is thought to predispose some individuals to recurrent acute or chronic pancreatitis, although many cases are asymptomatic.

The condition is typically identified incidentally on imaging, particularly MRCP, and may be classified into different types based on the degree of ductal non-fusion.

The term “divisum” derives from Latin dividere, meaning “to divide” or “to separate”.

Pathogenesis

During embryological development, the pancreas forms from two separate buds:

• The ventral bud gives rise to the inferior head and uncinate process
• The dorsal bud forms the superior head, neck, body, and tail

Normally, the ventral and dorsal ducts fuse by the 8th week of gestation, creating a single ductal system draining via the major papilla. In pancreas divisum:

• Ductal fusion fails, resulting in:
  • The dorsal duct of Santorini draining the body and tail via the minor papilla
  • The ventral duct of Wirsung draining only the inferior head and uncinate process via the major papilla
• The minor papilla, being small and less developed, may offer limited drainage capacity, leading to ductal hypertension and pancreatitis in a subset of patients

There is no associated genetic mutation or syndromic pattern.

Subtypes

• Type 1 (Classic pancreas divisum):
  • Complete failure of ductal fusion
  • Dorsal duct drains the majority of the gland via the minor papilla
• Type 2:
  • No connection between the dorsal and ventral duct
  • Ventral duct is rudimentary or absent
• Type 3 (Incomplete/functional pancreas divisum):
  • A small filamentous communication between dorsal and ventral ducts
  • Partial drainage may occur via both papillae

Epidemiology, Risk Factors & Associations

• Prevalence: 5–10% in the general population
• Equal sex distribution
• Usually asymptomatic
• Associated with:
  • Idiopathic recurrent acute pancreatitis
  • Chronic pancreatitis (especially in young patients without other risk factors)
  • Pancreatic-type pain without overt pancreatitis
  • Rare association with sphincter of Oddi dysfunction

Clinical Features

• Asymptomatic in most cases
• In symptomatic patients:
  • Recurrent episodes of acute pancreatitis
  • Chronic abdominal pain (epigastric or mid-abdominal)
  • Nausea and vomiting
  • Chronic pancreatitis with exocrine or endocrine insufficiency in late stages
• No pathognomonic physical signs
• Pancreatic enzyme elevations during acute episodes

Complications

• Recurrent acute pancreatitis
• Chronic pancreatitis with glandular fibrosis and atrophy
• Pancreatic ductal dilatation
• Parenchymal calcifications (in chronic cases)
• Formation of pancreatic pseudocysts
• Rarely, pancreatic divisum may mask or complicate pancreatic neoplasms

Pathological Features

Histopathology

• Not typically applicable unless biopsy or surgical resection performed
• Chronic pancreatitis changes may be present:
  • Fibrosis, ductal ectasia, acinar atrophy

Serology

• Amylase and lipase elevated during acute episodes
• IgG4 if autoimmune pancreatitis is in the differential

Biochemistry

• May show evidence of exocrine pancreatic insufficiency (e.g. low faecal elastase)

Immunohistochemistry

• Not used in routine diagnosis

Molecular

• No associated molecular markers

Genetics

• Not a genetically inherited condition
• Not associated with cystic fibrosis or other congenital duct anomalies

Radiological Features

General Features

• Ductal anatomy shows non-fusion of ventral and dorsal pancreatic ducts
• Dominant drainage via the minor papilla through the dorsal duct
• Ventral duct is short, draining only the inferior head/uncinate via the major papilla
• Most reliably identified using secretin-enhanced MRCP or ERCP
  • Secretin is a gastrointestinal hormone that stimulates the exocrine pancreas to secrete bicarbonate-rich fluid, enhancing visualisation of the pancreatic ductal system on MRCP.
  • Secretin-enhanced MRCP increases ductal calibre, particularly of the dorsal duct, improving the detection of pancreas divisum and minor papilla stenosis.
  • It also aids in functional assessment, allowing dynamic evaluation of pancreatic exocrine drainage and minor papilla outflow obstruction.

XR

• Not contributory
• May show calcifications if chronic pancreatitis is present

CT

• Non-contrast:
  • May appear normal
  • Chronic cases: parenchymal atrophy, calcifications
• C+ Arterial/Venous:
  • May show ductal dilatation
  • Occasionally, dual ducts may be inferred
  • Inferior head enhancement consistent with uncinate drainage via ventral duct

MRI

• T1:
  • Gland may appear normal or atrophic if chronic pancreatitis present
• T2:
  • Ducts appear as high signal fluid structures
• MRCP (non-enhanced):
  • Demonstrates separate dorsal and ventral ducts
  • Dorsal duct draining majority of pancreas via minor papilla
  • Absence of communication between the two ducts
• Secretin-enhanced MRCP:
  • Modality of choice
  • Enhances ductal distension, improves visualisation of minor papilla drainage
  • Helps evaluate functional drainage and identify minor papilla stenosis

US

• Limited sensitivity for ductal anomalies
• May identify ductal dilatation or chronic pancreatitis features

NM

• Not routinely used
• Functional evaluation of drainage may be done in experimental settings

Associated Findings

• Dorsal duct dilatation (>3 mm) if minor papilla is stenotic
• Signs of pancreatitis: peripancreatic fluid, gland swelling, necrosis
• Pseudocyst formation, especially in chronic or recurrent cases

Grading and Staging

• No formal grading system

Diagnosis

• Confirmed with MRCP, especially secretin-enhanced sequences
• ERCP may be used in selected cases (e.g. therapeutic intervention)
• Cross-sectional imaging supports diagnosis in symptomatic patients or complications

Differential Diagnosis

Image-based

• Annular pancreas:
  • Ring of pancreatic tissue encircling duodenum
  • May co-exist with pancreas divisum
• Santorinicoele:
  • Focal cystic dilatation of the dorsal duct at minor papilla
  • Seen with or without divisum
• Chronic pancreatitis:
  • Ductal dilatation, calcifications, parenchymal atrophy
  • Not exclusive to divisum
• Pancreatic ductal anomalies (bifid duct, ansa pancreatica):
  • Aberrant configurations but with communication between ducts

Clinically-based

• Functional dyspepsia
• Biliary colic
• Recurrent idiopathic pancreatitis
• Sphincter of Oddi dysfunction
• Pancreatic neoplasm (especially in setting of chronic pancreatitis)

Management

• Asymptomatic cases: no treatment required
• Symptomatic cases:
  • Endoscopic minor papilla sphincterotomy
  • Minor papilla stenting to improve drainage
• Recurrent pancreatitis or obstruction:
  • Endoscopic or surgical intervention
  • Longitudinal pancreaticojejunostomy (modified Puestow procedure) in chronic cases
• Multidisciplinary care involving gastroenterology, endoscopy, and surgery for complex cases