Ducts

2. Definition

Page 2 – Definition

Definition and Overview
• The bile ducts are a network of tubular structures that transport bile from the liver and gallbladder to the duodenum.
• They serve as a conduit system for bile excretion, essential for fat digestion and absorption.
• The system includes intrahepatic ducts (within the liver), extrahepatic ducts (common hepatic, cystic, and common bile duct), and terminates at the ampulla of Vater in the duodenum.

Core Elements	Details
Structure	Intrahepatic ducts, right and left hepatic ducts, common hepatic duct, cystic duct, common bile duct
Function	Bile transport, drainage from liver to duodenum
Common Diseases	Choledocholithiasis, cholangitis, biliary atresia, bile duct strictures
Diagnosis	Ultrasound, MRCP, ERCP, liver function tests
Treatment	Endoscopic stone removal, stenting, surgery, antibiotics (for infection)

 

3. Anatomy

Page 3 – Applied Anatomy and Diagnostic Approach

Table 1 – U-SSPCT–C (Structure in Discrete Bullet-Point Units)

Category	Units	Details
U – Units	Main ducts	• Right hepatic duct• Left hepatic duct• Common hepatic duct• Cystic duct• Common bile duct (CBD)
	Intrahepatic branches	• Segmental ducts within liver lobes
S – Size		• CBD: ~6 mm (may increase with age)• Length: varies from 5–15 cm depending on segment
S – Shape		• Tubular, flexible ducts• Converging system forming a Y or T configuration
P – Position		• Located within liver hilum and hepatoduodenal ligament• Ends at ampulla of Vater in duodenal wall
C – Character		• Hollow conduits• Lined by biliary epithelium• Sensitive to obstruction or inflammation
T – Time (Development & Aging)		• Formed during embryologic foregut development• Diameter increases slightly with age
C – Connections	Arterial Supply	• Cystic artery• Branches from hepatic artery
	Venous Drainage	• Portal vein tributaries
	Lymphatic Drainage	• Cystic and hepatic lymph nodes
	Nerve Supply	• Autonomic fibers from celiac plexus
	Joints	• Not applicable
	Ligaments & Tendons	• Contained within hepatoduodenal ligament

Imaging Modalities

Modality	Primary Use	When/Why Used
Ultrasound	First-line assessment of dilation or stones	Noninvasive and widely available
MRCP (MRI)	Detailed imaging of biliary tree	Detects strictures, stones, masses
ERCP	Diagnostic and therapeutic	Stone extraction, stent placement
CT	Assess mass lesions or biliary dilation	Often part of abdominal pain workup
HIDA scan	Functional test of bile flow	Biliary dyskinesia, cholecystitis

Laboratory Tests

Test	Purpose	When Used
Liver function tests (LFTs)	Detect cholestasis	Elevated ALP, GGT, bilirubin suggest bile duct obstruction
Bilirubin (direct/total)	Assess bile excretion	High in obstructive jaundice
AST/ALT	Assess hepatocellular injury	Can rise with concurrent hepatic disease
CBC	Check for infection	Elevated WBC in cholangitis

Other Diagnostic Tools

Tool	Use	Indication
Endoscopic ultrasound (EUS)	Evaluate distal CBD and ampulla	High-resolution imaging for tumors or small stones
Percutaneous cholangiography	Alternative imaging route	Post-surgical or obstructed anatomy
Intraoperative cholangiogram	Real-time surgical bile duct mapping	Prevent injury during cholecystectomy

4. Disease and Diagnosis

Page 4 – Clinical Diagnosis

1. Pathology (15-Category TCV Logic)

Category	Example Pathologies
Inflammatory/Immune	Primary sclerosing cholangitis
Infectious	Ascending cholangitis
Neoplastic – Benign	Biliary hamartoma
Neoplastic – Malignant	Cholangiocarcinoma
Mechanical	Biliary stricture, biliary obstruction
Trauma	Bile duct injury (e.g., post-cholecystectomy)
Metabolic	Bile duct stone formation (secondary to liver disease)
Circulatory	Ischemic cholangiopathy (post-transplant)
Inherited	Biliary atresia
Infiltrative	Sarcoidosis involving biliary tree
Idiopathic	Idiopathic benign recurrent intrahepatic cholestasis
Iatrogenic	Post-operative bile leak or stricture
Functional	Sphincter of Oddi dysfunction
Psychological	Functional abdominal pain mimicking biliary disease
Psychiatric	Non-specific symptoms with somatic overlay

2. Clinical Signs and Symptoms

Symptom	Implication
Jaundice	Obstruction of bile flow
Right upper quadrant pain	Common in cholangitis, stones
Fever + jaundice + pain (Charcot’s triad)	Ascending cholangitis
Clay-colored stools	Absence of bile in GI tract
Dark urine	Conjugated hyperbilirubinemia

3. Imaging Modalities

Modality	Use	Indication
Ultrasound	Detect duct dilation, stones	First-line in suspected obstruction
MRCP	Detailed duct visualization	Stones, masses, strictures
ERCP	Visualization + intervention	Biliary drainage, stent placement
CT	Evaluate associated masses	Tumor or pancreatitis-related obstruction

4. Laboratory Tests

Test	Purpose	When Used
LFTs (ALP, GGT, bilirubin)	Detect cholestasis	Obstructive or infiltrative disease
AST/ALT	Liver cell injury	May rise secondarily
WBC count	Detect infection	Cholangitis suspicion

5. Other Diagnostic Tools

Tool	Use	Indication
EUS	Detect distal CBD stones or masses	When other imaging is inconclusive
PTC	Direct cholangiography	Altered surgical anatomy
Manometry	Assess sphincter pressure	Suspected sphincter of Oddi dysfunction

5. History and Culture

Page 5 – History, Culture, and Art

1. History of Anatomy

Topic	Details
Ancient medicine	Bile recognized as one of the four humors
Modern anatomy	Detailed dissection and imaging refined understanding of bile duct system

2. History of Physiology

Topic	Details
Bile flow	Studied in digestive physiology since the 18th century
Bile acids	Key role in fat digestion elucidated in 20th century

3. History of Diagnosis

Topic	Details
Jaundice	Recognized as a symptom of bile obstruction for centuries
Cholangiography	Emerged as a diagnostic gold standard in mid-20th century

4. History of Imaging

Topic	Details
ERCP	Developed in the 1960s for diagnosis and therapy
MRCP	Noninvasive imaging alternative developed in 1990s

5. History of Laboratory Testing

Topic	Details
LFTs	Developed to monitor hepatobiliary health
Bilirubin	Key marker of bile obstruction and hemolysis

6. History of Therapies

Topic	Details
Cholecystectomy	Developed in 1882; bile duct exploration followed
ERCP intervention	Stenting and stone extraction revolutionized therapy

7. Cultural Meaning

Culture	Symbolism
Ancient humoral theory	Bile = aggression and vitality
Language	“Bilious” as a metaphor for bitterness or irritability

8. Artistic Representations

Artist/Context	Representation
Medical illustration	Color-enhanced bile duct trees in hepatobiliary atlases
Conceptual art	Flowing river motifs symbolizing health or obstruction

9. Notable Figures

Figure	Contribution
Walter W. Hogan	Pioneer in ERCP technique
Rudolf Virchow	Described obstructive jaundice pathology

10. Quotes

Quote	Attribution
“The bile ducts are the silent highways of digestion.”	Anonymous
“Flow, not force, defines a healthy system.”	AD

7. MCQ's

Page 6 – MCQs

Basic Science MCQ 1

Which structure delivers bile from the gallbladder to the common bile duct?

A. Common hepatic duct
B. Left hepatic duct
C. Cystic duct
D. Portal vein

Correct Answer	Explanation
C. Cystic duct	Connects gallbladder to the common bile duct allowing bile drainage or filling.

Incorrect Options	Why Incorrect
A. Common hepatic duct	Drains liver, not gallbladder
B. Left hepatic duct	Drains left lobe of liver
D. Portal vein	Blood vessel, not part of biliary system

Basic Science MCQ 2

What is the normal diameter of the common bile duct in adults?

A. 2 mm
B. 4 mm
C. 6 mm
D. 10 mm

Correct Answer	Explanation
C. 6 mm	This is generally accepted as the upper limit of normal, increasing slightly with age or post-cholecystectomy.

Incorrect Options	Why Incorrect
A. 2 mm	Too narrow for adults
B. 4 mm	Within range, but not upper limit
D. 10 mm	Suggests dilation or obstruction

Clinical MCQ 1

A patient presents with jaundice, fever, and right upper quadrant pain. What is the most likely diagnosis?

A. Hepatitis
B. Appendicitis
C. Cholangitis
D. Cholecystitis

Correct Answer	Explanation
C. Cholangitis	Charcot’s triad (pain, fever, jaundice) is classic for ascending cholangitis.

Incorrect Options	Why Incorrect
A. Hepatitis	May cause jaundice but not usually fever or pain
B. Appendicitis	Localizes to RLQ, not RUQ
D. Cholecystitis	No jaundice unless complicated by obstruction

Clinical MCQ 2

Which intervention is both diagnostic and therapeutic for obstructive jaundice?

A. ERCP
B. MRCP
C. CT scan
D. Ultrasound

Correct Answer	Explanation
A. ERCP	Allows direct visualization, stone removal, stenting of bile ducts.

Incorrect Options	Why Incorrect
B. MRCP	Diagnostic only
C. CT scan	Evaluates structures, not a therapeutic tool
D. Ultrasound	Initial screen, not interventional

Radiology MCQ 1

Which imaging modality is best to detect stones in the distal common bile duct in a post-surgical patient?

A. X-ray
B. ERCP
C. Ultrasound
D. MRI

Correct Answer	Explanation
B. ERCP	Gold standard for evaluation and treatment of distal CBD stones.

Incorrect Options	Why Incorrect
A. X-ray	Cannot visualize bile duct stones
C. Ultrasound	May miss distal stones
D. MRI	MRCP is useful but not therapeutic

Radiology MCQ 2

Which scan assesses bile excretion functionally rather than anatomically?

A. ERCP
B. CT scan
C. HIDA scan
D. MRI

Correct Answer	Explanation
C. HIDA scan	Demonstrates dynamic bile flow into duodenum — useful in assessing biliary function.

Incorrect Options	Why Incorrect
A. ERCP	Anatomical, not functional
B. CT scan	Structural only
D. MRI	MRCP shows ducts but not flow

Radiology MCQ 3

In which ligament are the extrahepatic bile ducts located?

A. Falciform ligament
B. Hepatoduodenal ligament
C. Gastrocolic ligament
D. Ligamentum teres

Correct Answer	Explanation
B. Hepatoduodenal ligament	Contains portal triad: hepatic artery, portal vein, and bile ducts.

Incorrect Options	Why Incorrect
A. Falciform ligament	Contains ligamentum teres only
C. Gastrocolic ligament	Part of greater omentum
D. Ligamentum teres	Remnant of fetal umbilical vein