Lecture Notes: Pancreas Anatomy, Physiology, and Ultrasound Imaging

Introduction

• Pancreas Functions: Dual function as an exocrine and endocrine organ.
• Imaging Challenges: Difficult to see by ultrasound due to its central and posterior position.

5.1 Global Anatomy

• Vascular Landmarks: Key for identifying pancreas by ultrasound.
• Development: Forms at week 4, functions by week 10; arises from dorsal and ventral embryonic buds.
• Location: Across back of abdomen, behind stomach; head lies on right side, tail extends to left near spleen.
• Anatomical Relations:
  • Anterior peri-renal space
  • Posterior: connective tissues, portal splenic confluence, superior mesenteric vessels, aorta, IVC, diaphragm
  • Superior/lateral: stomach, duodenum, transverse colon

5.2 Pancreas Anatomy

• Divided Into 5 Parts: Uncinate process, head, neck, body, tail.
• Landmarks: IVC, SMV, portal confluence, gastroduodenal artery, common bile duct.
• Individual Section Details:
  • Uncinate Process: Curved tip, located between IVC and SMV.
  • Head: Inferior, surrounded by duodenum; grooves for bile duct and artery.
  • Neck: Small, between head and body; posterior to SMV and portal confluence.
  • Body: Largest part, posterior to stomach; landmarks include aorta, celiac access, renal vein.
  • Tail: Near spleen, between spleen and left kidney.

5.3 Pancreatic Ducts

• Duct of Wirsung: Main pancreatic duct, joins bile duct.
• Duct of Santorini: Accessory duct, has separate duodenum entry.

5.4 Pancreatic Vasculature

• Blood Supply:
  • Head: Gastroduodenal artery.
  • Body/Tail: Splenic artery, superior mesenteric artery.
• Venous Drainage: Mainly by splenic vein; also superior/inferior mesenteric veins.

5.5 Variants

• Annular Pancreas: Pancreatic tissue surrounds duodenum.
• Ectopic Pancreas: Pancreatic tissue scattered in GI tract.
• Agenesis: Missing portions of pancreas, often dorsal.
• Pancreas Divisum: Dorsal and ventral portions not fused.

5.6 Microanatomy

• Exocrine Function: Acini cells produce digestive enzymes.
• Endocrine Function: Islets of Langerhans with alpha, beta, delta, gamma, epsilon cells.

5.7 Physiology

• Exocrine Function: Enzymes (amylase, lipase, proteases) produced by acini cells.
• Endocrine Function: Hormones (insulin, amylin, glucagon, somatostatin) regulate glucose levels.

5.8 Pancreas Chemistry

• Lab Tests: Amylase, lipase indicate pancreatic issues (e.g., pancreatitis).
• Endocrine Tests: Blood glucose levels used to assess insulin function.

5.9 Normal Appearance on Ultrasound

• Appearance: Echogenic, homogeneous, smooth texture.
• Landmarks: Uncinate process (IVC/SMV), head (GDA/CBD), neck (portal confluence), body (SMA/aorta), tail (splenic vein).
• Challenges: Obscured by gas; use liver as a window.

5.10 Pancreas Protocol

• Imaging Protocols:
  • Transabdominal Ultrasound: Use curvilinear probe; patient usually NPO.
  • Transesophageal Ultrasound: Used for detailed imaging; invasive.
• Scanning Tips: Use liver as a window, apply pressure to move bowel, adjust transducer angle for body/tail.
• Measurement: AP dimension < 3 cm; duct of Wirsung < 2 mm.

Conclusion

• Review and Practice: Engage in activities, use open-ended questions, and study images for better understanding.