Biliary Diseases

Published on 16/04/2015 by admin

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8 Biliary Diseases

Anatomy of the Extrahepatic Biliary System

image

Viscera: Gallbladder and Extrahepatic Ducts

• Anatomy of the biliary system is highly variable, and this includes ducts, arteries, veins, and lymphatics.

Common Hepatic Duct

• Intrahepatic biliary duct systems converge on right and left hepatic ducts.
• Right and left hepatic ducts typically form the common hepatic duct.
• Left duct is usually longer.
• Junction of the ducts may be intrahepatic (e.g., in hepatomegaly).
• Accessory hepatic ducts can occur.
• There may be no common hepatic duct if the cystic duct empties into right and left hepatic duct junction (bile duct branch variant).

Gallbladder

• Normally lies between hepatic segments IV and V, in a ventral fossa between the anatomical right and left lobes
• Ventral surface typically lies in contact with the descending part of the duodenum.
• Peritoneum surrounds fundus and attaches body and neck to the ventral surface of the liver.
• Hepatic surface of the gallbladder has fibrous tissue connections to liver capsule.
• Mucosa

image Columnar epithelium, no submucosa
image Actively absorbs Na+ and water, concentrating bile

• Smooth muscle of the fibromuscular layer is primarily oriented longitudinally.
• Parasympathetic preganglionic innervation from left (anterior) vagus fibers contracts gallbladder and relaxes bile duct sphincter.
• Postganglionic sympathetic fibers from the celiac ganglion are driven by preganglionic fibers from T7-T10 spinal segments traveling in greater splanchnic nerves.
• Visceral afferent fibers (e.g., pain) travel back toward thoracic spinal ganglia, through the celiac plexus and greater splanchnic nerve, alongside incoming sympathetics.

Cystic Duct

• Proximal portion is convoluted; spiral fold keeps the duct open.
• Distal portion is smooth.
• Typical cystic duct joins the common hepatic duct well below the right and left hepatic duct junction.
• Triangle of Calot: classic configuration (shown above) with cystic duct right, common bile duct left, liver above, and right hepatic artery passing through
image

Variations in Cystic and Hepatic Ducts

Cystohepatic Junction

• Classic normal

image High, sub-hepatic origin of the common hepatic duct
image Joined inferiorly, at an angle from the right, by the cystic duct (<3 cm)
image Produces the (common) bile duct some distance above the descending duodenum

• Variations

image Short or absent cystic duct
image Cystic duct parallel to hepatic duct
image Insertion into right hepatic duct
image Low insertion of cystic duct, crossing anterior to common hepatic duct, inserting behind the duodenum
image Low medial insertion of (anterior crossing) cystic duct into bile duct
image Low anterior insertion of (posterior crossing) cystic duct into bile duct

• Anatomical types of cystohepatic junction: angular, parallel, spiral

Ducts of Luschka

• Small biliary ducts that connect directly from liver to the gallbladder
• Potential source of leakage following cholecystectomy

(Common) Bile Duct

• Formed by the union of hepatic and cystic ducts
• Portions: supraduodenal, retroduodenal, pancreatic, intraduodenal
• Bile duct sphincter: smooth muscle surrounding the distal end of the duct, part of the complex sphincter of Oddi

Dimensions

• 4-8 mm diameter normal undilated
• Diameter tends to increase with advanced age.
• Heuristic: normal duct diameter in mm = age/10

Hepatopancreatic Ampulla (Vater)

• Formed by the union of the (common) bile duct and the main pancreatic duct
• Ampulla empties posteromedially through the major duodenal papilla (of Vater) into the retroperitoneal, descending (second) part of the duodenum.
• Hepatopancreatic sphincter (of Oddi): formed from a complex of smooth muscle surrounding the terminal part of the ampulla and its contributing duct

Bile Secretion

• Increased by cholecystokinin (CCK), secretin, and vagal activity
• Decreased by vasoactive intestinal peptide (VIP), somatostatin, sympathetic activity
• CCK causes tonic gallbladder contraction.
• Bile mediates absorption of fat-soluble vitamins and excretion of bilirubin and cholesterol.

Vessels and Lymphatics

image

Biliary System Arteries

Arteries

• Gallbladder is supplied by cystic artery, typically a branch of the right hepatic artery (from the hepatic artery proper, off common hepatic, celiac axis).
• Source and course of the cystic artery vary widely: this must be carefully determined in cholecystectomy.
• Variants include origins from common hepatic, left hepatic, superior mesenteric arteries, passing anterior or posterior to hepatic or bile ducts.
• Bile ducts: supplied by branches of posterior superior pancreaticoduodenal, retroduodenal, right, and left hepatic arteries (celiac axis)

Veins

• Cystic veins are variable; veins from the body typically pass directly into the liver to drain into hepatic sinusoids.
• Other veins from the neck and cystic duct typically drain directly into the right portal venous system, and other veins drain the biliary duct system.
image

Lymph Vessels and Nodes of Pancreas

Lymphatics

• Cystic lymph nodes cluster around the neck.
• Cystic lymphatics also drain into hepatic nodes clustered around the upper bile duct.
• Deeper drainage into celiac nodes around the arterial trunk

Clinical Correlates

Normal Bile Production

• 500 to 1000 mL/day
• Secretin production and meals rich in fats increase bile production.
• Bile constituents: electrolytes, bile salts, proteins, cholesterol, fats, and bile pigments
• Major salts: cholic, deoxycholic, and chenodeoxycholic acids; anionic and conjugated with taurine or glycine
• Contains unesterified cholesterol, lecithin, and fatty acids
• pH of 5.6-8.6 is normal range.

image More alkaline at higher secretion rates
image More acidic with protein in meals

• Cholesterol solubility and lack of stone precipitation depend on a balance among cholesterol, bile salts, and lecithin (in micelles).
• Gallbladder also secretes mucus, which protects tissues from the lytic action of bile.

Control of Bile Secretion

• Bile produced by the liver is shunted to the gallbladder, with the sphincter of Oddi tonically closed (between meals).
• Cholecystokinin is secreted by intestinal mucosa in response to ingestion of food.
• Gallbladder contracts and pushes bile into the ductal system.
• Sphincter of Oddi relaxes, and bile is released into duodenum.
image

Cholelithiasis

Cholelithiasis

• Incidence: about 10% of the population, with most asymptomatic
• Diabetics not at increased risk, though inflammatory responses can complicate late-detected cases, with higher incidence of open surgery
• Only about 10% of bile stones are radiopaque.
• Nonpigmented stones

image Most common type in U.S. (~75%)
image Increased insolubilization of cholesterol
image Factors can include cholestasis, increased H2O reabsorption, Ca2+ nucleation by mucin glycoprotein, and decrease in bile acids and lecithin.

• Pigmented stones

image Occurrence ~25% in U.S., most common worldwide
image Precipitation of calcium bilirubinate and insoluble salts, with solubilization of unconjugated bilirubin
image Black stones may be caused by cirrhosis, hemolytic disorders, ileal resection, or chronic total parenteral nutrition (TPN).
image Usually found only in the gallbladder

Diagnostic Procedures

• Liver and biliary function tests

image Serum alkaline phosphatase: very sensitive to obstruction; sensitivity increased by isoenzyme data blood levels
image Serum glutamic-oxaloacetic transferase (AST/SGOT) blood levels
image Serum glutamate-pyruvate transaminase (ALT/SGPT) blood levels
image Lactic acid dehydrogenase (LDH) blood levels
image Blood bilirubin levels

• Ultrasound

image Often the first test ordered for suspected biliary tract disease
image Safe, inexpensive
image 95% sensitivity for stones, identifies gallbladder morphology and mechanical vs. metabolic sources of jaundice

• Endoscopic retrograde cholangiopancreatography (ERCP)

image Catheter from a side-viewing endoscope is inserted into the ampulla of Vater.
image Contrast agent is injected.
image Radiographs are taken.
image Device can perform sphincterotomy if needed.
image Standing questions: What are indications for performing an ERCP before a lap chole? Blocked bile duct? May identify variants and reduce injuries?

Cholecystitis

• Gallbladder wall distention and inflammation
• Most common cause is obstruction of the cystic duct by a stone.
• Classic right upper quadrant pain referred to right scapula and shoulder
• Pain mediated by segmental visceral afferent fibers traveling with the splanchnic nerves (to thoracic spinal segments)
• Nausea, vomiting, loss of appetite, pain
• Symptoms often occur after fatty meal, with persistent pain.
• Murphy’s sign: patient resists deep inspiration owing to pain, with deep palpation of right upper quadrant
• Ultrasound ~95% sensitivity for stones
• Risk factors for stones: female, obesity, age >40 y, pregnancy, rapid weight loss, vagotomy, TPN, ileal resection

Cholecystectomy

• Laparoscopic cholecystectomy (lap chole) has been the treatment of choice for many years, preferred to formerly traditional open cholecystectomy.
• Complicated laparoscopic case may be converted to an open cholecystectomy.
• Open cholecystectomy uses conventional surgical instruments with a right upper quadrant or midline abdominal incision.
• Lap chole essentials

image General anesthesia, sub-umbilical incision for CO2 (insufflation) trocar
image 3 trocars placed (for laparoscope and specialized tools) in right subcostal region
image Retraction of gallbladder, incision of triangle of Calot
image Dissection and ligation of cystic duct and artery
image Dissection and removal of gallbladder

• Most common bile duct injuries associated with laparoscopic cholecystectomy

image (Common) bile duct mistaken for cystic duct and transected
image Variable extent of extrahepatic biliary tree excised with gallbladder
image Right hepatic artery injured with dissection

Gallstone Pancreatitis

• Estimated 40% of acute pancreatitis cases result from transient obstruction of pancreatic duct flow by stones blocking bile duct or ampulla of Vater.
• Mechanism of such pancreatitis not known
• Symptoms: epigastric and radiating back pain, nausea, vomiting, elevated serum lipase and amylase levels
• Treatment can complicate the timing of a related cholecystectomy.
• ERCP may be needed if an impacted ampulla is suspected.

Carcinoma of the Biliary Tract

• Can occur at any point along the intra- or extrahepatic biliary tree and gallbladder
• Gallbladder carcinoma is the most common biliary cancer and the fifth most common GI cancer.

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8 Biliary Diseases

Anatomy of the Extrahepatic Biliary System

image

Viscera: Gallbladder and Extrahepatic Ducts

• Anatomy of the biliary system is highly variable, and this includes ducts, arteries, veins, and lymphatics.

Common Hepatic Duct

• Intrahepatic biliary duct systems converge on right and left hepatic ducts.
• Right and left hepatic ducts typically form the common hepatic duct.
• Left duct is usually longer.
• Junction of the ducts may be intrahepatic (e.g., in hepatomegaly).
• Accessory hepatic ducts can occur.
• There may be no common hepatic duct if the cystic duct empties into right and left hepatic duct junction (bile duct branch variant).

Gallbladder

• Normally lies between hepatic segments IV and V, in a ventral fossa between the anatomical right and left lobes
• Ventral surface typically lies in contact with the descending part of the duodenum.
• Peritoneum surrounds fundus and attaches body and neck to the ventral surface of the liver.
• Hepatic surface of the gallbladder has fibrous tissue connections to liver capsule.
• Mucosa

image Columnar epithelium, no submucosa
image Actively absorbs Na+ and water, concentrating bile

• Smooth muscle of the fibromuscular layer is primarily oriented longitudinally.
• Parasympathetic preganglionic innervation from left (anterior) vagus fibers contracts gallbladder and relaxes bile duct sphincter.
• Postganglionic sympathetic fibers from the celiac ganglion are driven by preganglionic fibers from T7-T10 spinal segments traveling in greater splanchnic nerves.
• Visceral afferent fibers (e.g., pain) travel back toward thoracic spinal ganglia, through the celiac plexus and greater splanchnic nerve, alongside incoming sympathetics.

Cystic Duct

• Proximal portion is convoluted; spiral fold keeps the duct open.
• Distal portion is smooth.
• Typical cystic duct joins the common hepatic duct well below the right and left hepatic duct junction.
• Triangle of Calot: classic configuration (shown above) with cystic duct right, common bile duct left, liver above, and right hepatic artery passing through
image

Variations in Cystic and Hepatic Ducts

Cystohepatic Junction

• Classic normal

image High, sub-hepatic origin of the common hepatic duct
image Joined inferiorly, at an angle from the right, by the cystic duct (<3 cm)
image Produces the (common) bile duct some distance above the descending duodenum

• Variations

image Short or absent cystic duct
image Cystic duct parallel to hepatic duct
image Insertion into right hepatic duct
image Low insertion of cystic duct, crossing anterior to common hepatic duct, inserting behind the duodenum
image Low medial insertion of (anterior crossing) cystic duct into bile duct
image Low anterior insertion of (posterior crossing) cystic duct into bile duct

• Anatomical types of cystohepatic junction: angular, parallel, spiral

Ducts of Luschka

• Small biliary ducts that connect directly from liver to the gallbladder
• Potential source of leakage following cholecystectomy

(Common) Bile Duct

• Formed by the union of hepatic and cystic ducts
• Portions: supraduodenal, retroduodenal, pancreatic, intraduodenal
• Bile duct sphincter: smooth muscle surrounding the distal end of the duct, part of the complex sphincter of Oddi

Dimensions

• 4-8 mm diameter normal undilated
• Diameter tends to increase with advanced age.
• Heuristic: normal duct diameter in mm = age/10

Hepatopancreatic Ampulla (Vater)

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