Biliary System anatomy Ultrasound Perspective

Biliary System Ultrasound Anatomy

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The biliary system anatomy refers to the visualization and evaluation of the ducts and associated structures responsible for the transport and storage of bile, primarily using grayscale and Doppler sonography.
1. Biliary System Components
The biliary system includes the following components:

• Gallbladder (GB): A pear-shaped organ that stores bile.
• Cystic Duct: Connects the gallbladder to the common bile duct.
• Common Hepatic Duct (CHD): Formed by the junction of the right and left hepatic ducts.
• Common Bile Duct (CBD): Carries bile from the liver and gallbladder to the duodenum.
• Intrahepatic Ducts: Bile ducts within the liver that merge to form the right and left hepatic ducts.

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2. Ultrasound Visualization
Transabdominal ultrasound is the standard imaging modality:

• The gallbladder is best seen in the fasting state to ensure it's distended.
• The common bile duct is visualized anterior to the portal vein in the portal triad.
• The normal intrahepatic ducts are typically not seen unless dilated.

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3. Normal Ultrasound Appearance
Gallbladder:

• Anechoic, fluid-filled structure with thin walls (≤3 mm).
• Should not contain internal echoes (unless there are stones/sludge).

The gallbladder (GB) is a pear‐shaped structure located in the GB fossa, a depression on the visceral surface of the liver between the right and left lobe. The GB is usually lateral to the second part of the duodenum and anterior to the right kidney (RK). (b) Note is made of the main interlobar fissure (IF) between the portal vein (PV) and the GB.
Common Bile Duct (CBD):

• Anechoic tubular structure, best seen in the longitudinal plane.
• Located anterior to the portal vein and hepatic artery (part of the portal triad).

The common bile duct (CBD) can be seen as a thin tubular structure with echogenic walls that, in the majority of cases, runs anteriorly and parallel to the portal vein (PV) at the level of the hepatic hilum. The hepatic artery (HA) is often seen at this level in transverse section, hence it is visualised as a small rounded or ovoid structure (depending on the angle of insonation) with echogenic walls between the CBD and the PV. CBD Normal Diameter by Age:

Age Group	Normal Diameter
Children	≤ 2 mm
Adults (under 60)	≤ 6 mm
Post-cholecystectomy	Up to 10 mm

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4. Common Pathological Findings
Gallstones (Cholelithiasis):

• Hyperechoic foci with posterior acoustic shadowing.
• Mobile with patient position changes.

Cholecystitis:

• Thickened gallbladder wall (>3 mm).
• Pericholecystic fluid or sonographic Murphy’s sign (tenderness on probe pressure).

Biliary Obstruction:

• Dilated intrahepatic ducts ("parallel channel" or "double barrel" sign).
• CBD >6 mm (without surgery history), >10 mm if post-cholecystectomy.

Choledocholithiasis:

• Stone(s) within the CBD.
• Seen as echogenic foci with posterior shadowing within duct.

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5. Techniques for Optimal Biliary Imaging

• Patient Preparation: Fasting for 6–8 hours helps distend the gallbladder.
• Patient Positioning: Supine and left lateral decubitus positions improve visualization.
• Probe: Curvilinear transducer (2–5 MHz) for adults; higher frequency linear probe for thin patients or children.
• Scanning Tips: Use multiple angles (subcostal, intercostal) to evaluate CBD and intrahepatic ducts clearly.

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6. Clinical Relevance

• Gallstones: May cause biliary colic or acute cholecystitis if they obstruct the cystic duct.
• CBD Stones: Can cause obstructive jaundice, pancreatitis, or cholangitis.
• Cholecystitis: Prompt diagnosis on ultrasound prevents complications like gallbladder perforation.
• Postoperative Biliary Dilation: Slightly enlarged CBD is normal post-cholecystectomy unless associated with symptoms.

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7. Biliary System Doppler Use
Doppler is not routinely used for biliary imaging but may help:

• Differentiate vascular structures from bile ducts.
• Confirm avascularity of gallbladder masses or sludge (vs. polyps or tumors).

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Topic related exam

Portal Vein Ultrasound – MCQ Quiz

Note: If you select English, answer all questions in English.
यदि आप हिंदी चुनते हैं, तो सभी प्रश्न हिंदी में हल करें।

1. Which structure stores bile? 1. पित्त कहाँ स्टोर होता है?
A. Gallbladder / गॉलब्लैडर
B. Hepatic vein / हेपेटिक वेन
C. Portal vein / पोर्टल वेन
D. Cystic duct / सिस्टिक डक्ट

2. On ultrasound, how does the common bile duct (CBD) appear? 2. अल्ट्रासाउंड पर कॉमन बाइल डक्ट (CBD) कैसे दिखता है?
A. Anechoic tubular structure / एनीकोइक ट्यूबुलर स्ट्रक्चर
B. Hyperechoic tubular structure / हाइपेरइकोइक ट्यूबुलर स्ट्रक्चर
C. Isoechoic structure / आइसोइकोइक स्ट्रक्चर
D. Echogenic circular mass / इकोजेनिक सर्कुलर मास

3. What is the normal wall thickness of the gallbladder? 3. गॉलब्लैडर की सामान्य दीवार मोटाई क्या है?
A. ≤3 mm / ≤३ मिमी
B. ≥5 mm / ≥५ मिमी
C. 6–8 mm / ६–८ मिमी
D. Variable with age / उम्र के अनुसार परिवर्तनशील

4. What is the typical sonographic appearance of gallstones? 4. पित्ताश्म की सामान्य सोनोग्राफिक दिखावट क्या है?
A. Hyperechoic with posterior shadowing / हाइपेरइकोइक + शैडो
B. Anechoic with enhancement / एनीकोइक + एन्हांसमेंट
C. Hypoechoic without shadow / हाइपोइकोइक बिना शैडो
D. Isoechoic with no shadow / आइसोइकोइक बिना शैडो

5. What is the “parallel channel” sign indicative of? 5. “पैरलल चैनल” साइन किसके लिए सूचक है?
A. Dilated intrahepatic bile ducts / फैलें हुए इंट्राहेपेटिक बाइल डक्ट्स
B. Normal hepatic veins / सामान्य हेपेटिक वेन्स
C. Portal vein thrombosis / पोर्टल वेन थ्रोम्बोसिस
D. Cirrhosis / सिरोसिस

6. What is the upper limit of normal CBD diameter in a post-cholecystectomy patient? 6. चोलेकिसिस्टेक्टॉमी के बाद सामान्य CBD व्यास की अधिकतम सीमा क्या है?
A. 10 mm / १० मिमी
B. 15 mm / १५ मिमी
C. 8 mm / ८ मिमी
D. 6 mm / ६ मिमी

7. Which of the following structures is NOT normally visualized as an anechoic tube on ultrasound? 7. इनमें से कौन सा संरचना सामान्यतः अल्ट्रासाउंड पर एनीकोइक ट्यूब के रूप में दिखाई नहीं देता?
A. Gallbladder wall / गॉलब्लैडर की दीवार
B. Hepatic vein / हेपेटिक वेन
C. Hepatic artery / हेपेटिक आर्टरी
D. Portal vein / पोर्टल वेन

8. The cystic duct connects the gallbladder to which structure? 8. सिस्टिक डक्ट गॉलब्लैडर को किस संरचना से जोड़ता है?
A. Common hepatic duct / कॉमन हेपेटिक डक्ट
B. Duodenum / डुओडेनम
C. Pancreatic duct / पैनक्रियाटिक डक्ट
D. Portal vein / पोर्टल वेन

9. What does pericholecystic fluid with gallbladder wall thickening suggest? 9. गॉलब्लैडर की मोटी दीवार और उसके आसपास फ्लुइड का क्या संकेत है?
A. Cholecystitis / कोलेसिस्टाइटिस
B. Biliary colic / बाइलरी कोलिक
C. Portal hypertension / पोर्टल हायपरटेंशन
D. Hepatic cyst / हेपेटिक सिस्ट

10. Which of the following best uses Doppler in biliary imaging? 10. बाइलरी इमेजिंग में डॉप्लर का मुख्य उपयोग क्या है?
A. To differentiate vessels from ducts / वेसल और डक्ट में अंतर
B. To measure bile flow / पित्त प्रवाह मापना
C. To detect gallstones / पित्ताश्म का पता लगाना
D. To measure GB wall / गॉलब्लैडर दीवार मापना