Imaging Anatomy of the Pancreas Ben Barnard Department of Diagnostic Radiology; KHC

Outline  Embryology  Variants  Gross anatomy  Anatomical relations  Arterial supply  Venous drainage  Lymphatic drainage  Radiological anatomy

Embryology  The pancreas is formed by dorsal and ventral buds originating from the endodermal lining of the duodenum  The smaller ventral bud arises in conjunction with the bile duct and consists of two portions  Left bud which atrophies during development  Right bud which swings posteriorly and unites with the inferior division of the dorsal bud

Langman’s Medical Embryology

Variants  Agenesis of the dorsal pancreatic moeity  Pancreas with a head but no body or tail – very rare  Left-sided pancreas  Effect of age with laxity of suspensory fascia  Accessory nodules (pancreatic rests)  Can occur in the wall of the stomach, duodenum, jejunum, appendix, Meckel’s diverticulum (1-15% )  Pancreas divisum  Failure of fusion of dorsal and ventral moeities  Anterosuperior head and body drain via accessory ampulla  Posterioinferior head drains to ampulla  Annular pancreas

Annular pancreas  Occurs when the left portion of the ventral bud fails to atrophy and migrates around the duodenum in the opposite direction to the normal right portion  Duodenum is thus surrounded bypancreatic tissue, and an annular pancreas is formed  This tissue constricts the duodenum and may cause complete obstruction

Gross Anatomy  Retroperitoneal organ  15cm long  Transverse mesocolon originates from anterior surface.

 Head  C-curve of duodenum (L2)  Uncinate process  Inferior-medial extension of head under SMA (L2)  Neck  Overlies L1 vertebral body immediately to the left of the head  Body  Extends left and slightly superior (L1)  Tail  Tapering portion extending to hilum of spleen (T12)

Various normal shapes

Anatomical Relations  Anterior relations  Peritonium  1 st part duodenum  Lesser sac and stomach  Transverse colon/mesocolon

Anatomical Relations  Posterior relations  CBD  IVC  PV  Aorta  SMA  SMV  Right renal vein  Left kidney  Crurae of diaphragm.

Retroperitoneal Compartments  The pancreas (P) lies in the anterior pararenal space (APRS) together with the ascending and descending colon (C) and duodenum  ST = stomach  S = spleen  RK = right kidney  LK = left kidney  A = aorta  V = inferior vena cava  LS = lesser sac  PRS = perirenal space  PPRS = posterior pararenal space

Grants Anatomy

Pancreatic duct  Pancreatic duct measures  3mm in the head  2mm in the neck  1mm in the tail  Unites with the common bile duct to form the ampulla of Vater and opens into the 2 nd part of duodenum

Pancreatic duct variants  Santorini  Wirsung

Arterial supply  Pancreas neck, body and tail  Dorsal pancreatic artery (from splenic artery or coeliac trunk)  Pancreatica magna artery ( emerges halfway along the splenic artery)  Transverse pancreatic artery (travels along the length of the pancreatic duct and anastomoses with the above arteries)  Pancreas head  Superior pancreaticoduodenal artery (anterior and posterior branches from the gastroduodenal artery)  Inferior pancreaticoduodenal artery (anterior and posterior branches from the superior mesenteric artery)

Venous drainage  SMV  Splenic vein  Portal vein

Lymphatic drainage  Along arterial blood supply to pre-aortic coeliac lymph nodes

Radiological anatomy

US  MHz probe  Sagittal, transverse and oblique planes  Occasionally, may have non-visualization due to bowel gas which can be overcome by: 1. Fill stomach with fluid 2. Position patient erect (liver descends) 3. Prone position for tail

CT  Similar density as liver  Density is reduced with increasing age due to normal accumulation of fat  Homogenous enhancement post contrast

MRI

ERCP

MRCP

References Imaging Anatomy of the Pancreas Referaat, Dr Frans Naude Normal Findings in CT and MRI,Moeller Pocket Atlas of Sectional Anatomy Computer Tomography and Magnetic Resonance Imaging, Torsten B. Moeller, MD Last’s anatomy 11 th ed, Sinnatamby Applied radiological anatomy, Butler Atlas of human anatomy, F Netter Pocket Atlas of Radiographic Anatomy,second edition,Moeller Atlas of normal rontgen variants that may simulate disease, R Keats Color Atlas of Ultrasound Anatomy,Berthold Block Grant atlas of anatomy