Pancreatic sonographic anatomy

1. PANCREATIC SONOGRAPHIC
anatomy
Dr.mohamed soliman

2. General Anatomic Considerations
• Pancreas is non-encapsulated, retroperitoneal structure
that lies in anterior pararenal space
• Obliquely in transverse plane spanning between duodenal
loop and splenic hilum
• Level changes on respiratory movement
o Craniocaudal shifting of 2-8 cm may occur on respiration
• Length - 12-15 cm across
• Pancreas can be identified & localized on ultrasound by
o Typical parenchymal architecture, homogeneously
isoechoic/hyperechoic echotexture
o Surrounding anatomical landmarks: Anterior to splenic vein,
SMA

3. Critical Anatomic Structures
• Anatomical division
o Head: Parenchyma to the right of superior mesenteric
vessels
o Uncinate process: Represents medial extension of head
• Lies posterior to superior mesenteric vessels
o Neck: Narrow portion anterior to superior mesenteric
vessels
• Serves as dividing line between pancreatic head and body
o Body: Parenchyma to left of superior mesenteric vessels
• Constitute main bulk of pancreatic parenchyma
o Tail: Most distal portion of pancreatic parenchyma
• No clear anatomic landmark separates tail from body

4. Critical Anatomic Structures•
Histological division
o Functionally the pancreas comprised of
exocrine and endocrine tissues
• 80% exocrine tissue; ductal and acinar cells
• 2% endocrine tissue; islet cell of Langerhans
• 18% fibrous stroma containing blood vessels,
nerves and lymphatics

5. Anatomic Relationships
• Pancreas is closely related to several important
structures/ organs
o Gastrointestinal tract & peritoneal spaces
• Anteriorly: Stomach, transverse colon and
root of transverse mesocolon, lesser sac
• Right: Duodenal loop (esp. second part of
duodenum)

6. Anatomic Relationships - Major vessels
• Abdominal aorta: Posterior to body of pancreas
• Coeliac axis: Related to superior border of pancreas
• Common hepatic artery: Branch of coeliac axis, related to superior border of
pancreatic neck and head
• Gastroduodenal artery: Branch of coeliac axis, coursing inferiorly anterior to
pancreatic head
• Splenic artery: Branch of coeliac axis, towards the left in tortuous course along superior
border of pancreatic body and tail
• Superior mesenteric artery (SMA): Arises from abdominal aorta just caudal to
inferior border of pancreas, descends anterior to uncinate process
• Inferior vena cava: Posterior to head of pancreas
• Splenic vein: Coursing transversely from splenic hilum to portal vein confluence posterior
to pancreatic tail and body
• Superior mesenteric vein: Ascends to right of SMA anterior to uncinate process
• Portal vein: Confluence posterior to pancreatic neck, proximal portion above superior
margin of pancreatic head

7. Anatomic Relationships - Common bile duct
• Distal portion posterior to or embedded within
pancreatic head
• Forms common trunk with pancreatic duct in
80% to drain into ampulla of Vater

8. Imaging technique
• Transabdominal ultrasound serves as a useful initial imaging modality for
suspected pancreatic lesion
• Advantages of US
o Readily available o Relatively inexpensive imaging technique
o Does not involve ionizing radiation o Supplemented with Doppler US to identify
abnormal flow (thrombosis, tumor encasement) or abnormal vascularity
(tumor vascularity)
o Use as real time imaging guide for interventional procedures
• Disadvantages of US
o Pancreas is retroperitoneal structure and considered "deep" intra abdominal
organ for imaging with transabdominal ultrasound
o Limited US beam penetration in obese patient with thick subcutaneous and
omental fat
o Often entire pancreatic parenchyma cannot be completely examined due to
overlying bowel gas
o Operator-dependent imaging technique

9. Technical consideration in transabdominal US
o Examination should begin in transverse plane in midline below
xiphisternum, using vascular landmarks to identify pancreas
• Longitudinal view for further evaluation particularly if lesion is
detected
o Pancreatic body can usually be better delineated by transducer
pressure to displace overlying bowel gas
o If there is abundant bowel gas obscuring pancreatic parenchyma
• Scanning with patient in various positions including erect,
sitting, both obliques and decubitus may help
• Ask patient to drink plenty of water to distend the
stomach which acts as an acoustic window

10. Technical consideration in transabdominal US
o Using left kidney/spleen as acoustic window,
pancreatic tail can be visualized in left coronal view
o Head can be better assessed through right
lateral/decubitus approach in a coronal plane
o Place area of interest within the focal zone of
transducer
o Always examine the rest of the abdomen in detail
o Doppler US to aid assessment of patency and
flow characteristics of vessels

11. • Special US techniques such as endoscopic US
(EUS) or intra-operative US (IOU) are useful in
detecting small pancreatic tumors (e.g., islet
cell tumor) which are not apparent on
transabdominal US, CT or MR

12. • Cross-sectional imaging techniques including CT and MR are
usually required for further characterization of pancreatic
lesion detected on US
• Advantages of CT
o Fast scanning in era of multi-detector CT, thus more
practical in critically ill patients
o Shows calcifications better than other imaging modalities
o Less prQne to technical and interpretative errors
• Advantages of MR
o No ionizing radiation is involved
o Does not require iodinated contrast agent
o Multiplanar capability
o Allows easy evaluation of common bile duct and
pancreatic duct using MRCP sequences

13. PATHOLOGY-BASED IMAGING ISSUES
• Two main categories to differentiate on imaging
include neoplasm (most commonly ductal pancreatic
carcinoma) and pancreatitis
o Ductal pancreatic carcinomas typically cause
narrowing or obstruction of vessels and ducts, and
extend dorsally to coeliac axis and SMA origins
o Acute pancreatitis causes fluid exudation and fat
infiltration, extends ventrally and laterally to mesentery
and anterior pararenal space, less common cause for
ductal obstruction

14. Differential diagnoses of cystic pancreatic mass
o Common
• Pseudocyst
• Mucinous cystic tumor
• Serous cystadenoma
• Necrotic pancreatic ductal carcinoma
• Intraductal papillary mucinous tumor (IPMT)
o Uncommon
• Simple/congenital cyst (e.g., Von Hippel Lindau syndrome, adult
polycystic kidney disease)
• Solid and papillary neoplasm of pancreas
• Lymphangioma
• Cystic metastases/lymphoma

15. Conditions to consider if dilated pancreatic duct is
seen
o Chronic pancreatitis: Parenchymal or intraductal
calcification, atrophic pancreas
o Pancreatic ductal carcinoma: Common bile and
pancreatic ductal dilatation for most common
lesions in pancreatic head
o Periampullary tumor
o IPMT
o Obstructing distal common bile duct (CBD) stone

16. Embryologic Events
• Embryologically, pancreas is developed from dorsal and ventral
pancreatic buds
o Body-tail segment developed from dorsal pancreatic bud
o Head-uncinate segment developed from ventral pancreatic bud
• During normal development, ventral bud migrates dorsally
around fetal duodenum to merge with dorsal bud to form
pancreatic substance and branching pancreatic and bile ducts
Practical Implications
• Failure or anomalies of rotation or fusion may result in congenital
lesions such as annular pancreas, pancreas divisum, agenesis of
dorsal pancreas
• Ventral (head-uncinate) and dorsal (body-tail) segments may have
different echotexture that may be misinterpreted as pathology
• Pancreatic ductal obstruction of either dorsal or ventral buds may
lead to dilatation of involved portion with sparing of uninvolved
segments

17. Clinical Importance
• Ductal pancreatic carcinoma: Usually presents late with
poor overall prognosis, surgically not operable in most cases
• Serous cystadenoma: No malignant potential,
microcystic/macrocystic in appearances
• Mucinous cystic pancreatic tumor: Regarded as pre-malignant
lesion, predominantly cystic with septations +/- solid
component
• Islet cell tumor: Hypervascular primary tumor and liver
metastases, most common
o Insulinoma, functional tumors small at presentation
o Non-functional tumors large at diagnosis
• Solid and papillary neoplasm, metastases, lymphoma;
rare lesions

18. Pancreas measurement

20. liver
HA SA
aorta
IVC
pancreas
sv
PV

21. liver
pancreas
PV confluence
SMA
aorta
IVC

22. PV
SMA
IVC aorta

23. Transverse
transabdominal
ultrasound shows
anatomical relationship
of the pancreas to the
splenic vein SMA portal
vein confluence
abdominal aorta and IVC
pancreas
SMA SV
PV confluence
aorta
IVC

24. Transverse
transabdominal
ultrasound shows the
normal anatomical
relationship of the
uncinate process which
is medial extension of
pancreatic head
behind the SMV
SMA pancreatic neck.
pancreatic neck
SMV
uncinate process
SMA

25. Transverse
transabdominal
ultrasound shows
normal pancreatic tail
with homogeneous
echotexture.
pancreatic tail
SV
SMA
IVC
Aorta

26. Transverse
transabdominal
ultrasound performed
with a high-frequency
transducer in a thin
patient shows a non-dilated
pancreatic duct
within the pancreatic
body.

27. Transverse
transabdominal ultrasound
shows the homogeneous
echotexture of the pancreas
in a healthy patient. Note
the lack of pancreatic ductal
dilatation and parenchymal
masslcalcification.
pancreas

28. Transverse
transabdominal
ultrasound shows an
ill-defined hypoechoic
carcinoma in the
pancreatic
head causing obstruction
and dilatation of the
pancreatic duct .
Pancreatic head
pancreatic duct

29. Transverse
transabdominal ultrasound
shows global swelling with
a
diffusely hypoechoic echo
pattern of the pancreas =
suggestive of acute
pancreatitis. Note presence
of small peri-pancreatic
fluid
peri-pancreatic fluid
peri-pancreatic fluid

30. Transverse
transabdominal
ultrasound
shows calcifications
within the pancreatic
parenchyma in patient
with
chronic pancreatitis
related
to alcohol abuse.

31. Transverse
transabdominal
ultrasound shows the
well-circumscribed,
unilocular, cystic lesion
in the pancreatic tail. The
rest of the pancreas is
unremarkable.
Pathology:Pseudocyst.
cystic lesion
in the pancreatic tail

32. Transverse
transabdominal
ultrasound shows a
well-circumscribed,
solid, hyperechoic
mass in pancreatic
tail
hyperechoic mass in
pancreatic tail