Diagnostic Ultrasound - Abdomen and Pelvis

Biliary System
• Harmonic imaging provides improved contrast between
bile ducts and adjacent tissues, leading to improved
visualization of bile ducts, luminal content, and wall
• For imaging of gallstone disease, special maneuvers are
recommended
○ Move patient from supine to left lateral decubitus
position
– Demonstrates mobility of gallstones
– Gravitates small gallstones together to appreciate
posterior acoustic shadowing
○ Set focal zone at level of posterior acoustic shadowing
– Maximizes effect of posterior acoustic shadowing
Imaging Approaches
• Transabdominal ultrasound is ideal initial investigation for
suspected biliary tree or GB pathology
○ Cystic nature of bile ducts and GB (especially if these are
dilated) provides inherently high-contrast resolution
○ Acoustic window provided by liver and modern state of
the art ultrasound technology provides good spatial
resolution
○ Common indications of US for biliary and GB disease
include
– Right upper quadrant/epigastric pain
– Abnormal liver function test or jaundice
– Suspected gallstone disease
– Pancreatitis
○ US plays key role in multimodality evaluation of complex
biliary problems
• Supplemented by various imaging modalities including
MR/MRCP and CT
Imaging Pitfalls
• Common pitfalls in evaluation of GB
○ Posterior shadowing may arise from GB neck, Heister
valves of CD, or adjacent gas-filled bowel loops
– Mimics cholelithiasis
– Scan after repositioning patient in prone or left lateral
decubitus positions
○ Food material within gastric antrum/duodenum
– Mimics GB filled with gallstones or GB containing milk
of calcium
– During real-time scanning, carefully evaluate
peristaltic activity of involved bowel with oral
administration of water
• Common pitfalls in US evaluation of biliary tree
○ Redundancy, elongation, or folding of GB neck on itself
– Mimics dilatation of CHD or proximal CBD
– Avoided by scanning patient in full suspended
inspiration
– Careful real-time scanning allows separate
visualization of CHD/CBD medial to GB neck
○ Presence of gas-filled bowel loops adjacent to distal
extrahepatic bile ducts
– Obscure distal biliary tree and render detection of
choledocholithiasis difficult
– Scan with patient in decubitus positions or after oral
intake of water
○ Gas/particulate material in adjacent duodenum and
pancreatic calcification
– Mimic choledocholithiasis within CBD
○ Presence of gas within biliary tree
– May mimic choledocholithiasis, differentiated by
presence of reverberation artifacts
– Limits US detection of biliary calculus
Key Concepts
• Direct venous drainage of GB into liver bypasses portal
venous system, often results in sparing of adjacent liver
from generalized steatosis (fatty liver)
• Nodal metastasis from GB carcinoma to peripancreatic
nodes may simulate a primary pancreatic tumor
• Sonography: Optimal means of evaluating GB for stones
and inflammation (acute cholecystitis); best done in fasting
state (distends GB)
• Intrahepatic bile ducts follow branching pattern of portal
veins
○ Usually lie immediately anterior to portal vein branch;
confluence of hepatic ducts just anterior to bifurcation
of right and main portal veins
CLINICAL IMPLICATIONS
Clinical Importance
• In patients with obstructive jaundice, US plays key role
○ Differentiates biliary obstruction from liver parenchymal
disease
○ Determines presence, level, and cause of biliary
obstruction
• Common variations of biliary arterial and ductal anatomy
result in challenges to avoid injury at surgery
○ CD may run in common sheath with bile duct
○ Anomalous right hepatic ducts may be severed at
cholecystectomy
• Close apposition of GB to duodenum can result in fistulous
connection with chronic cholecystitis and erosion of
gallstone into duodenum
Function & Dysfunction
• Obstruction of common bile duct is common
○ Gallstones in distal bile duct
○ Carcinoma arising in pancreatic head or bile duct
○ Result is jaundice due to back up of bile salts into
bloodstream
Embryologic Events
• Abnormal embryological development of fetal ductal plate
can lead to spectrum of liver and biliary abnormalities
including
○ Polycystic liver disease
○ Congenital hepatic fibrosis
○ Biliary hamartomas
○ Caroli disease
○ Choledochal cysts
SELECTED REFERENCES
1. Shackelford RT: Shackelford’s Surgery of the alimentary tract. 7th edition.
Elsevier/Saunders, 2013
2. Standring S et al: Gray's anatomy: the anatomical basis of clinical practice.
Edinburgh: Churchill Livingstone/Elsevier, 2008
Anatomy: Abdomen
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