Pancreas Ultrasound: Anatomy, Imaging, and Pathology (Chapters 1–8)

Pancreas location and regional anatomy

• Pancreas sits mostly in the epigastric region; tail may extend into the left hypochondriac region. Head is more posterior; tail is relatively superior.
• Pancreas lies in a complex way relative to surrounding structures; the differential in ultrasound comes from how the beam cuts through the organ.
• In the body’s nine abdominal regions, the pancreas is primarily in the epigastric region, with the tail crossing into the left hypochondriac region.

Pancreas anatomy in transverse ultrasound

• In transverse view, the pancreas appears with the tail more superior than the head; the head is posterior in this orientation.
• Uncinate process is a small hook-like projection inferior/medial to the head; the neck lies on top of the curve; the body is between the neck and tail.
• Transverse imaging often does not show the entire head or uncinate process due to the beam’s cut; you may see only the neck, body, and tail.
• The ductal and vascular relationships you see depend on the slice; the pancreatic tail sits posterior to some vessels.

Vascular landmarks around the pancreas (landmarks to identify on ultrasound)

• Portal confluence (portal vein formation): where the splenic vein and superior mesenteric vein (SMV) join to form the portal vein. In transverse view, you often see the portal confluence rather than the individual vessels unless you rotate to the long axis.
• Splenic vein: runs posterior to the body and tail of the pancreas; joins the portal vein at the portal confluence.
• Superior mesenteric artery (SMA): located anterior to the uncinate process; appears as a bright, circular, hyperechoic border due to collagen.
• Aorta: posterior to the pancreas and a landmark just off to the left of the SMA in cross-section; aorta and IVC are posterior to the pancreas.
• Left renal vein: lies between the SMA and the aorta; anterior to the aorta and posterior to the SMA (a classic cross-sectional landmark).
• Common bile duct (CBD) and gastroduodenal artery (GDA): in the head of the pancreas; seen as two anechoic circles in transverse; GDA is near the head and often anterior to some structures; CBD is also adjacent to the head and is a key landmark in head imaging.

Pancreatic ducts and ductal anatomy

• Ducts of the pancreas:
  • Wirsung (pancreatic duct): runs the length of the pancreas; joins the common bile duct and drains at the ampulla of Vater into the duodenum.
  • Santorini (accessory pancreatic duct): an auxiliary duct that drains part of the head and joins the main duct; together they drain into the duodenum via the common bile duct route.
• Ducts join and drain toward the duodenum via the ampulla of Vater.
• Divisum: ducts of the pancreas do not communicate normally; pancreatic drainage is divided (non-communication between the main and accessory ducts).
• Ectopic pancreatic tissue can occur (pancreatic tissue outside the normal location).
• Annular pancreas: ventral pancreatic tissue encircles the duodenum, which can constrict the duodenum and cause obstruction.

Pancreas shape, orientation, and everyday landmarks

• The pancreas generally lies in this configuration: head and neck near the duodenum, body central, tail toward the left upper quadrant.
• The head sits in the “lap” of the duodenum; the uncinate process lies posterior to the superior mesenteric vessels and toward the spine.
• The tail tends to be superior and posterior relative to the head.
• Directional relationships to remember:
  • Head: anterior to the IVC? (described as inferior to the main portal vein and right of the portal confluence, and medial to the second part of the duodenum).
  • Neck: anterior to the portal confluence or SMV/SV junction.
  • Body: anterior to the aorta and celiac axis; the splenic artery lies along the superior border of the gland and is tortuous.
  • Tail: lateral to the left kidney and near the spleen; the splenic vein runs along the posterior border of the pancreas.
• The duct system and the bile duct cross near the head; common bile duct and GDA are often the small anechoic circles seen in transverse near the head.
• The pancreas lies in the lap of the stomach/duodenum in life; gas can obscure ultrasound visualization.

Pancreatic endocrine vs exocrine function

• Exocrine pancreas: produces digestive enzymes (lipase, amylase, proteases) and bicarbonate; enzymes travel via ducts (Wirsung/Santorini) to the duodenum.
• Endocrine pancreas: islets of Langerhans secrete hormones (insulin, glucagon, somatostatin) directly into the bloodstream.
• The islets are composed of alpha and beta cells (beta cells produce insulin).
• Insulin and glucose exchange: insulin binds to receptors, opens glucose gates to allow glucose entry into cells.

Pancreatic neoplasms and lesions (overview by type)

• Endocrine (islet cell) neoplasms (often secretory):
  • Insulinoma: produces insulin; hypoglycemic symptoms; most common functioning islet cell tumor.
  • Gastrinoma: secretes gastrin; causes gastric acid overproduction, ulcers, heartburn; often malignant; second most common functioning islet cell tumor.
  • Glucagonoma, somatostatinoma: rarer functioning tumors.
  • MEN1 syndrome: endocrine tumor syndrome affecting pituitary, adrenal, thyroid, parathyroid; pancreas involvement common; multiple endocrine neoplasia type 1.
• Endocrine tumors (non-functioning) and other neuroendocrine tumors may occur; the terminology emphasizes islet cell origin.
• Exocrine pancreatic adenocarcinoma: pancreatic cancer arising from exocrine tissue; poor prognosis, especially when in the head due to ductal dilation and early symptom onset; often metastasizes to liver; lymph nodes around the aorta may be enlarged.
• Lymphoma and other retroperitoneal neoplasms can involve the pancreas; appearances vary (hypoechoic masses, enlarged lymph nodes near vessels).
• Cystic lesions of the pancreas:
  • Serous cystadenoma (microcystic; typically benign; serous fluid-filled cysts).
  • Mucinous cystadenoma (macrocystic; potentially malignant); often in the body/t tail.
  • Intraductal papillary mucinous neoplasm (IPMN): originates in or near pancreatic ducts; may be benign or malignant; involves ducts and branches.
• Other cystic lesions: cystic fibrosis-related pancreatic cysts; polycystic disease; pancreatic lymphangiomas; cystic teratomas.

Pancreatitis and related complications on ultrasound

• Acute pancreatitis:
  • May show an enlarged pancreas with altered echotexture (often hypoechoic edema).
  • Labs: elevated amylase and lipase; urine amylase may be checked.
  • Complications: pseudocysts; abscess formation; hemorrhagic changes with hemorrhagic pancreatitis (pancreatic tissue may appear heterogeneous with areas of echogenic blood products).
• Chronic pancreatitis:
  • Coarse, heterogeneous echotexture; calcifications within the gland; ductal dilation; gland may become smaller due to fibrosis.
  • Pseudocysts are common in chronic pancreatitis.
  • Chronic pancreatitis carries increased risk for pancreatic cancer.
• Ductal changes can include dilation of the pancreatic duct due to obstruction from fibrosis/calcifications.

Specific imaging findings and signs discussed

• Courvoisier sign (often misspelled in notes as “Porvirciet”): non-tender, palpable, distended gallbladder with jaundice, typically indicating obstruction from pancreatic head mass.
• Pancreatic duct dilation and CBD dilation may accompany head lesions; dilated biliary system and jaundice suggest obstructive process.
• Pseudocysts, abscess, phlegmon (inflammation), and peritonitis risk with pancreatic disease.
• Antemortem ultrasound findings may be subtle; CT or MRI is preferred for cancer detection and staging; ultrasound often used first due to cost/access and to avoid unnecessary CTs/MRIs if possible.

Imaging technique and patient preparation tips

• Ultrasound limitations: gas in stomach/duodenum and bowel can obscure pancreas; thus an ultrasound window is sometimes improved by stomach filling.
• When: patient is NPO; water can be given to fill the stomach, creating a “window” for better visualization of the pancreas (often with the patient in the right lateral decubitus to move the stomach and gas away from the pancreas).
• If visualization is poor, CT or MRI is used for detailed assessment of suspected pancreatic disease, especially cancer.
• In practice, many clinics perform US first (insurance-driven), then CT/MRI if needed.
• The normal pancreas is typically measured in AP (anterior-posterior) orientation in transverse imaging; measurements are often reported for head, neck, body, and tail.
• Typical normal size:
  • Normal pancreatic size: 3\,\text{cm} (overall standard; some sources vary with measurement technique).
  • Pancreatic duct: generally < 2\,\text{mm} (some sources cite <3 mm depending on protocol).
  • Common bile duct: typically size thresholds vary by patient; some notes mention measurement without a fixed unit; clinical practice varies and color Doppler is used to differentiate ducts from vessels.
• Typical ultrasound protocol views include:
  • Transverse pancreas view showing head, neck, body, tail with landmarks (aorta, IVC, SMA, portal confluence, splenic vein).
  • Longitudinal view (less commonly used for pancreas than transverse) to assess extent and ducts; coin purse view of neck/uncinate process (SMV between neck and uncinate).
• Key landmarks to identify in practice:
  • Head and neck in relation to the portal confluence and SMV; neck anterior to the portal confluence.
  • Body anterior to the aorta and the celiac axis; tortuous splenic artery along the superior border.
  • Tail near the left kidney and lateral to the spleen; splenic vein on the posterior border.
  • Ducts and CBD near the head (Wirsung and Santorini; CBD near ampulla of Vater).

Normal measurements, echotexture, and interpretation cues

• Echotexture: normal pancreas is typically homogeneous and smooth in texture.
• Echogenicity: pancreas is usually hyperechoic relative to liver in some patients; the liver is darker than pancreas; spleen is variable depending on patient.
• Pancreas size and interpretation:
  • Head is the largest of the four parts; measure AP, verify size thresholds.
  • Ducts: Wirsung and Santorini are assessed with color Doppler to distinguish from vessels; if a duct looks like a vessel on gray-scale, color Doppler helps confirm.
• What you look for when a mass is suspected:
  • Ill-defined borders, ductal dilation, vascular involvement, lymph node enlargement around the aorta, liver metastases.
• Normal vs abnormal for cancer risk:
  • Pancreatic cancer risk and poor prognosis increase when a mass is found in the head; tail lesions may be harder to detect early due to limited surrounding anatomy to compress.

Pancreatic ductal adenocarcinoma and related cancer concepts

• Common site and signs:
  • Head lesions: may cause obstructive jaundice and Courvoisier sign; dilation of pancreatic and common bile ducts; gallbladder changes.
  • Tail/body lesions: often present later; may present with pain or weight loss rather than jaundice.
• Metastasis and lymph nodes:
  • Lymph nodes around the aorta are commonly enlarged in pancreatic cancer and portend a poor prognosis.
  • Metastasis to liver is common; prognosis is generally poor after diagnosis.
• Lymphoma and other retroperitoneal tumors can involve the pancreas; appearances vary widely on ultrasound.

Whipple procedure (pancreaticoduodenectomy)

• Indication: tumors or serious disease in the head of the pancreas or the uncinate process; also applied in select benign conditions.
• Basic steps described in the video:
  • Access the abdomen via upper midline incision.
  • Kocher maneuver to mobilize duodenum and head of the pancreas; identify inferior vena cava (IVC).
  • Remove gallbladder; transect across the intestine and at the neck of the pancreas and the common bile duct to remove the specimen.
  • Reconstruct: pancreaticojejunostomy (pancreas to jejunum), choledochojejunostomy (bile duct to jejunum), and gastrojejunostomy (stomach to jejunum).
  • Variant: pylorus-preserving Whipple (preserve pylorus and connect stomach differently).
  • Approaches can be open, laparoscopic, or robotic; open is the time-tested standard.
• Postoperative pancreatic remnant imaging considerations:
  • After resection, the remaining pancreas (body and tail) is imaged to verify anatomy and ensure no residual disease; calcifications may be seen in the tail.

Practical takeaways and exam-ready notes

• Expect ultrasound to be less than ideal for full pancreatic evaluation; CT/MRI is preferred for cancer.
• When you do ultrasound of the pancreas, use water-in-stomach technique to create a window and rotate patient to optimize views.
• Remember: the pancreas is a mixed organ with both endocrine and exocrine functions; islet cells secrete insulin, glucagon, somatostatin; acini cells secrete digestive enzymes.
• Ducts are crucial: Wirsung (main duct) and Santorini (accessory); they drain into the duodenum via the ampulla of Vater; Divisum and annular pancreas are congenital variants to be aware of.
• Normal pancreas size is around 3\,\text{cm}; the pancreatic duct is typically < 2\,\text{mm} (some protocols allow up to 3 mm); CBD diameter thresholds vary but are typically small in a healthy state.
• Always differentiate ducts from vessels with color Doppler when you see a circular anechoic structure near the pancreas.
• Be mindful of directional anatomy: SMA crosses anterior to the uncinate process; left renal vein lies between SMA and aorta; splenic vein runs posterior to the pancreas and joins the portal vein at the portal confluence.
• Inflammatory and cystic pancreatic diseases can mimic or accompany each other (pseudocysts in pancreatitis, serous/mucinous cystadenomas, IPMNs).
• Endocrine pancreatic neoplasms are uncommon but important; insulinomas are the most common functioning islet cell tumor; gastrinomas cause ulcers and GI symptoms.
• Pancreatic cancer prognosis is generally poor, especially for tail tumors; head tumors may present earlier due to biliary obstruction; lymph nodes and liver metastases worsen prognosis.
• Whipple procedure overview: major operation to remove head/duodenum with reconstruction; examine remaining pancreas (body/tail) for disease post-resection; can be open, laparoscopic, or robotic.

Quick reference summary (one-liners)

• Pancreas location: epigastric region; tail into left hypochondriac; head posterior.
• Major ducts: Wirsung (main), Santorini (accessory); drain into ampulla of Vater with CBD.
• Key landmarks: SMA (anterior to uncinate), portal confluence (SV+SMV), splenic vein (posterior to pancreas), left renal vein (between SMA and aorta).
• Normal size: about 3\,\text{cm}; duct < 2\,\text{mm} (±3 mm in some protocols).
• Pancreatitis: acute (edematous, enlarged), chronic (calcifications, coarse echotexture, duct dilation).
• Tumors: neuroendocrine (insulinoma, gastrinoma, etc.) vs exocrine adenocarcinoma; prognosis worse for tail lesions; head lesions cause biliary obstruction.
• Imaging strategy: US first; CT/MRI for cancer; water window technique to improve visualization; consider duodenoscope views for special ductal anatomy.
• Whipple procedure: pancreaticoduodenectomy with pancreaticojejunostomy, choledochojejunostomy, gastrojejunostomy; pylorus-preserving variant exists; open technique is standard.