the pancreas. i.introduction/general information a. located in epigastric & left hypochondriac...

THE PANCREAS

I. Introduction/General Information

A. Located in epigastric & left hypochondriac regions

B. Dimensions:1. 5 - 6” length x 2. 1-1/2” width x 3. 1/2 - 1” thick

C. Lies retroperitoneally at ~T-12/L-1 to L-3

The Pancreas in situ

Right lobe of liver

Falciform ligament

Gallbladder

Pancreas

Duodenum

L-3

Pancreas, Introduction, continued …

D. Head fills concavity of duodenum

E. Body crosses left kidney

F. Tail reaches hilus of the spleen

G. Related anteriorly to transverse colon

Pancreas in situ

Duodenum

Head of Pancreas

Pancreas, Introduction, continued …

H. Aorta, IVC lie posterior

I. Uncinate process:

a. Lies posterior to SMA and SMV

b. Lies anterior to aorta

J. Neck lies anterior to SMV, with pylorus just above

Venous Drainage of the Pancreas

IVC

SMV

Introduction, continued

L. Body related posteriorly to left crus, left adrenal, left renal vein, and splenic vein

K. Celiac Axis (trunk, artery) lies superior to body

II. Detailed Anatomy

A. Landmark structures

1. Splenic Artery:

a. Branch of celiac trunk

b. passes right to left

c. Course is along upper margin of body and tail

Detailed Anatomy, con’t…

2. Hepatic Artery: a. Branch of celiac trunkb. courses left to right c. along upper margin of neck and

head

3. Superior Mesenteric Artery: at its origin from aorta, points at body of pancreas

Arterial Supply to Pancreas

Common Hepatic Artery

Proper Hepatic Artery

Superior Mesenteric Artery

Landmark structures, continued …

4. Splenic Vein: a. runs parallel to artery b. on posterior surface of pancreasc. Terminates in portal vein

Landmark structures, continued …

5. Superior & Inferior Mesenteric Veins: a. pass (inferior to superior) deep

to pancreas

b. merge with splenic vein

c. Terminate in portal vein

Landmark structures, continued …

6. Common Bile Duct: a. passes behind first portion of

duodenum b. then through head of pancreasc. Terminates at ampulla of vater

Detailed Anatomy continued …

B. Head of Pancreas

1. Important clinically because:a. Numerous ducts and vessels traverse it b. Carcinoma usually located here

Head of Pancreas, Detailed Anatomy, continued …

2. Tumor will compress surrounding structuresa. First indication may be jaundiceb. Tumor may compress

duodenumc. May involve local vessels

*Metastases may spread through these vessels*

Head of Pancreas, Detailed Anatomy, continued …

3. Lymphatics from head of pancreas

a. Drain to celiac nodes

b. metastases may follow lymph

c. Metastases may spread via lesser omentum to liver

d. Some terminate in lumbar nodes

Head of Pancreas, Detailed Anatomy, continued …

4. Vessels supplying head of pancreas a. Superior & inferior pancreaticoduodenal arteriesb. Both divide into two parallel

vessels c. one anterior and one posterior to

head

Head of Pancreas, Detailed Anatomy, continued …

1. Anterior branch of pancreaticoduodenal artery

a. superior branch:anterior superior

pancreaticoduodenal arteryb. inferior branch:

anterior inferior pancreaticoduodenal artery

Head of Pancreas, Detailed Anatomy, continued …

2. Posterior branch of pancreaticoduodenal artery

a. superior branch:posterior superior

pancreaticoduodenal artery

b. inferior branch:posterior inferior

pancreaticoduodenal artery

**extensive blood supply**

Anterior Pancreaticoduodenal Artery

•Branches are continuous with one another

•Superior branches originate from the GDA

•Inferior branches originate from the SMA

Detailed Anatomy, continued …

C. Body & Tail of Pancreas:

1. Supplied by splenic artery 2. Have three surfaces:

a. Anterior surface 1. Concave2. Deep to stomach3. Separated from stomach

by lesser sac of peritoneum (aka omental bursa)

Anterior surface of pancreas

Anterior surface of pancreas

Epiploic foramen

Lesser sac, continued …

4. Lesser sac bounded by:a. Liver, superiorlyb. Below, extends to greater omentumc. Anteriorly: lesser omentum, stomach,

greater omentum

Lesser sac, continued …

d. Posteriorly: greater omentum transverse colon, transverse mesocolon

e. Laterally:

1. Foramen of Winslow on right

2. Spleen on left

Detailed Anatomy, continued …

f. Foramen of Winslow (AKA: Epiploic Foramen):

1. Lies between greater & lesser sacs of peritoneum

2. posterior to free edge of lesser omentum

3. close to porta hepatis

Three Surfaces, continued …

2. Posterior surface: separated from vertebrae by

a. Aortab. Splenic vein c. Left kidney and renal vesselsd. Left adrenal glande. Left Crus of diaphragmf. SMA and SMV

Three surfaces, continued …

3. Inferior surface of Pancreatic body:a. Rests on duodeno-jejunal flexureb. Left extremity (tail)

1. Rests on splenic flexure2. Abuts hilus of spleen

Detailed Anatomy, continued …

D. Pancreatic Duct System

1. Pancreatic Duct (of Wirsung) a. Course is left to right b. Receives numerous small ductsc. @ neck of pancreas, duct turns

inferior, posterior & to the right

d. AKA “main pancreatic duct’

Duct of Wirsung (Main pancreatic duct)

Pancreatic Duct System, continued …

d. joins CBD at Ampulla of Vater 3 - 4” below pylorus

e. results from fusion of ducts during fetal development

1. One from ventral pancreas

2. One from dorsal pancreas

(see Netter’s Embryology, p. 142, for Pancreas development)

Duct of Wirsung

Duct of Wirsung

Pancreatic Duct System, continued …

2. Duct of Santorini:

a. accessory pancreatic duct

b. Not universally identified

c. joins duodenum @ minor papilla

d. part of duct from dorsal pancreas

Duct of Santorini

Pancreatic Duct System, continued …

3. In 10% of population a. ducts fail to fuse b. result is drainage of tail, body, &

most of head through minor papillac. Not pathological

III. Scanning Anatomy

A. Depends on recognition of pancreaticmargins

B. Sonography best used as screening procedure

1. May be interference from bowel gas (especially in tail region)

Scanning Anatomy, continued …

2. Extremely accurate in detection of pseudocysts

3. U/S can show texture of organ

4. By ID-ing vessels, can delineate head, portions of body

Scanning Anatomy, continued …

5. U/S can frequently detect dilation of pancreatic duct

6. Splenic Vein: landmark vessela. usually seen along posterior

margin of body, tailb. May be anterior (~30%)

Scanning Anatomy, continued …

C. Head: 1. SMV outlines medial head to neck

region2. Duodenum & GB outline lateral head3. Superiorly, delineated by gastroduodenal artery (GDA)4. Inferiorly, bounded by CBD

Scanning Anatomy, continued …

D. Further delineation by vascular landmarks:

1. SMA: a. Lies immediately posterior to body, points to it! b. Recognized by echogenic fat

collar surrounding vessel

Vascular Landmarks of the Pancreas

Pancreatic sonography depends largely on identifying surrounding landmark vessels

Scanning Anatomy, continued …

2. SMV: a. Delineates medial head b. Larger diameter than SMA c. Lies to right of SMA

d. Uncinate process wraps it (and SMA), lies posterior & medial

Vascular Landmarks of the Pancreas

Venous landmarks of the pancreas include the SMV and renal veins

Scanning Anatomy, continued …

3. Left Renal Vein:a. as it enters IVC b. head & uncinate process should lie within 1 – 2 cmc. Landmark vessel posterior

to body of pancreas

Scanning Anatomy, continued …

E. Tail of Pancreas

1. May be visualized through fluid-filled stomach

2. Tail seen as 2-3 cm rounded mass anterior to hilus of left

kidney

IV. Pancreatic Disorders

A. Pancreatitis: diagnosis depends on clinical evidence

1. Usually secondary to biliary tract disease

2. Surgery of biliary tract or stomach, alcoholism are other causes

Pancreatitis, Pancreatic Disorders, continued …

3. Infrequent causes:a. Infectious diseases b. Trauma d. Drugs

e. Hyperparathyroidism

4. Inflammation may be diffuse or spotty

Pancreatitis, Pancreatic Disorders, continued …

5. Important factor is release of protein kinins

a. Increase permeability of vessels & cellsb. Releases tissue fluid c. Edema may compress vesselsd. Tissue damage occurs

Pancreatitis, Pancreatic Disorders, continued …

6. WBC’s may increase to 20,000/ml

7. Increase in pancreatic enzymes

a. serum bilirubinase (by 25%)

b. serum amylase

c. serum lipase

Pancreatic Disorders, continued …

B. Pseudocysts:

1. “False” cysts that may arise

a. due to tissue necrosis

b. From enzymatic destruction

2. May persist after inflammation subsides

3. Usually near or in pancreas

Pancreatic Disorders, continued …

4. Rarely, may be elsewhere

a. in abdomen or pelvis

b. Rarely, mediastinum

5. Pseudocyst appearance

a. unilocular or multilocular

b. echoes from pus & cellular debris

Pancreatic Diseases, continued

C. Acute Pancreatitis

1. Diffuse enlargement

2. Less echogenic due to edema

3. Echogenicity usually > liver parenchyma

Pancreatic Diseases, continued …

D. Chronic Pancreatitis

1. organ usually appears as small, atrophic

2. Contains scattered echoes from calcifications

3. Primary cause is alcoholism

Pancreatic Diseases, continued …

E. Dilation of Pancreatic Duct

1. Seen in acute or chronic pancreatitis

2. Frequently associated with neoplasm of pancreas

3. Biliary tract problems

Pancreatic Diseases, continued …

F. Abscess or Hemorrhagic Pancreatitis 1. Similar in sonographic appearance 2. Hemorrhagic:

a. Mass with inhomogeneous texture b. Acute hemorrhage: sonolucent to

echogenic c. CT scan used for differentiation

Pancreatic Disorders, continued …

G. Pancreatic Tumors

1. Malignant tumors usually arise as adenocarcinomas

2. In head of Pancreas: Sxa. Painless jaundiceb. Anorexia

Pancreatic Tumors, In head, continued …

c. Nausea

d. Weight loss

e. Increased plasma amylase

f. Increased alkaline phosphatase

g. May involve compression of pancreatic duct, CBD

Pancreatic Tumors in the Head

Tumors in the head may compress biliary ducts or pancreatic ducts

Pancreatic tumors, continued …

3. In Body of Pancreas: Sxa. Gnawing pain radiating to backb. Pain increases after eating or lying downc. Weight loss, anorexiad. Large tumor may compress IVC, portal vein

Pancreatic tumors, continued …

4. In Tail of Pancreas: Sxa. Often silent until local metastasis occursb. May metastasize to: 1. para-aortic lymph nodes

2. spleen

Pancreatic tumors, continued …

5. Identified by organ enlargement, subtle echo changes, irregular outline

6. Metastases to stomach, liver & lungs are common

7. Often causes dilation of ducts

Pancreatic Disorders, continued …

H. Fibrocystic Disease

1. Result of cystic fibrosis

2. Diagnosed by methods other than ultrasound

Pancreatic Disorders, continued …

I. Pancreaticolithiasis

1. Characteristic stone echoes in pancreatic duct

2. May see atrophied pancreatic parenchyma

3. Associated with chronic alcoholic pancreatitis

4. Contours of body, tail show irregularities

Pancreatolithiasis, continued …

5. Incidence slightly higher in head

6. Associated with occult pancreatic carcinoma

a. Mass < 2mm diameter

b. Seen with dilation of pancreatic duct or CBD