Pancreas: Accessory digestive gland lying behind stomach in anterior pararenal space (APS) of retroperitoneum

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  Exocrine function: Pancreatic acinar cells secrete pancreatic juice → pancreatic duct → duodenum

  
  
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  Endocrine: Pancreatic islet cells (of Langerhans) secrete insulin, glucagon, and other polypeptides → portal venous system

Head: Thickest part; lies to right of superior mesenteric artery and vein (SMA, SMV)

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  Attached to “C” loop of duodenum (2nd and 3rd parts)

  
  
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  Uncinate process: Head extension, posterior to SMV

  
  
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  Bile duct lies along posterior surface of head, joins with pancreatic duct (of Wirsung) to form hepatopancreatic ampulla (of Vater)

  
  
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  Main pancreatic and bile ducts empty into major papilla in 2nd portion of duodenum

Neck: Thinnest part; lies anterior to SMA, SMV

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  SMV joins splenic vein behind pancreatic neck to form portal vein

Body: Main part; lies to left of SMA, SMV

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  Splenic vein lies in groove on posterior surface of body

  
  
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  Anterior surface is covered with peritoneum forming back surface of omental bursa (lesser sac)

Tail: Lies between layers of splenorenal ligament in splenic hilum

Pancreatic duct (of Wirsung) runs length of pancreas, turning inferiorly through head to join bile duct

Accessory pancreatic duct (of Santorini) opens into duodenum at minor duodenal papilla

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  Usually communicates with main pancreatic duct

  
  
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  Variations are common, including dominant accessory duct draining most pancreatic juice

Vessels, nerves, and lymphatics

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  Arteries to head mainly from gastroduodenal artery

  
  
  
  
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    Pancreaticoduodenal arcade of vessels around head also supplied by SMA branches

  
  
  
  
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  Arteries to body and tail from splenic artery

  
  
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  Veins are tributaries of SMV and splenic vein → portal vein

  
  
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  Autonomic nerves from celiac and superior mesenteric plexus

  
  
  
  
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    Parasympathetic stimulation of pancreatic secretion, but pancreatic juice secretion is mostly under hormonal control (secretin, from duodenum)

  
  
  
  
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  Lymphatics follow blood vessels

  
  
  
  
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    Collect in splenic, celiac, superior mesenteric and hepatic nodes

  
  

Pancreas can be localized on ultrasound by

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  Typical parenchymal architecture: Homogeneously isoechoic/hyperechoic echo pattern when compared with overlying liver

  
  
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  Surrounding anatomical landmarks: Body anterior to splenic vein; neck anterior to SMA/SMV

Variations in reflectivity related to degree of fatty infiltration; uncinate process and posterior pancreatic head are relatively echo poor in 25% of subjects (lack of intraparenchymal fat)

Use 2- to 5-MHz transducers or up to 9 MHz for smaller patients

Techniques to combat overlying stomach and bowel gas include

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  Displacement of intervening bowel gas by gentle graded compression with transducer

  
  
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  Overnight fasting or fasting > 6-8 hours

  
  
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  Noneffervescent fluid can be given orally to fill gastric fundus

  
  
  
  
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    Scanning delayed for few minutes to allow fluid to settle

    
    
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    Patient can lie on left side to allow imaging of body and tail of pancreas

    
    
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    Patient can then be turned right to allow gastric fluid to flow to stomach antrum and duodenum, allowing imaging of head and uncinate process

  
  

CT is preferred imaging modality for imaging of pancreas

MRCP (± secretin) or ERCP useful for defining pancreatic duct

Ultrasound examination of pancreas is often limited by overlying bowel gas

Shape, size, and texture of pancreas are quite variable

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  Largest in young adults

  
  
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  Atrophy and fatty infiltration with age (> 70), obesity, diabetes, corticosteroids, Cushing disease

  
  
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  Pancreatic duct also becomes more prominent with age (normal < 3 mm diameter)

  
  
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  Focal bulge or mass effect is abnormal

Location behind lesser sac

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  Acute pancreatitis often results in lesser sac fluid (may mimic pseudocyst)

Pancreas lies in APS

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  Inflammation (from pancreatitis) easily spreads to duodenum and descending colon, which are also located in APS

  
  
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  Inflammation easily spreads into mesentery and mesocolon; roots of these lie just ventral to pancreas

Obstruction of pancreatic duct

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  Relatively common result of chronic pancreatitis (fibrosis &/or stone occluding pancreatic duct) or pancreatic ductal carcinoma

Acute pancreatitis

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  Relatively common result of gallstone (lodged in hepatopancreatic ampulla causing bile to reflux into pancreas) or damage from alcohol abuse