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FIGURE 7.1. Embryologic development of the biliary tree.
3. The sphincter of the ampulla, the grouping of longitudinal and circular muscles around the ampulla of
Va te r.
4. The duodenal wall surrounding the intramural CBD.
Ducts of Luschka
Small bile ducts may drain directly from the liver into the
GB. The significance of these ducts of Luschka lies in their
ability to cause postcholecystectomy bile leak or biloma if
they are unrecognized and not ligated.
ANOMALIES OF THE BILIARY TREE
Gallbladder
Congenital absence of the GB is rare (0.03% in autopsy
studies). Also rare are the duplication of the GB with single
or double cystic duct, a GB that is abnormal in location,
and a left-sided GB. Not uncommonly, it is partially intrahepatic and completely intrahepatic in rare cases.
Cystic Duct
In three out of four individuals, the cystic duct enters the
CBD at right angles. In the remainder, it may run parallel
to the CBD for variable distances or enter the CBD on the
left by passing either in front of or behind it (Figure 7.3).
E mbryology and Anatomy .................................................................................................................... 199
Common Bile Duct
Congenital cystic anomalies may affect the entire biliary
tract. These rare anomalies are of three types:
1. Cystic dilation of the entire CBD (choledochal cyst).
2. Localized cystic malformation of a portion of the CBD,
usually distally.
3. Diffuse fusiform dilation of the CBD.
Biliary Atresia
Congenital biliary atresia involves both the intra- and
extrahepatic biliary tree. It is estimated to occur in
FIGURE 7.2. Anatomy of the choledochal sphincter. The complex structure of the choledochal sphincter is made up of the choledochal sphincter, the pancreatic duct sphincter, the sphincter of the
ampulla, and the duodenal wall surrounding the intramural common bile duct. (Adapted from Netter
FH. Icon Learning Systems Atlas of Human Anatomy, Ciba-Geigy, 1989. All rights reserved.)
1 : 20,000 live births and is associated with malformations
in other organs.
Blood Supply
The GB is supplied by the cystic artery, a branch of the
right hepatic artery in 95% of individuals and located in
the triangle of Calot. Rarely, the cystic artery may originate from the gastroduodenal artery. There may also be
two cystic arteries, with one often originating from the
right hepatic and the other from the left hepatic or gastroduodenal artery (Figure 7.4).
Nerve Supply
The GB receives extrinsic innervation from both the sympathetic and the vagus nerves. Sympathetic innervation is
from the celiac axis and distributed on the adventitia of
arteries. Vagal innervation is largely from the hepatic
branches of the right vagus, but some vagal innervation is
also distributed in the gastrohepatic omentum from the
celiac axis. The vagal fibers are cholinergic and peptidergic. The intrinsic innervation (analogous to the enteric
nervous system) is a network of nerves in the wall of the
gall bladder that utilize a variety of neurotransmitters,
chief among which are cholinergic and peptidergic.
200 .................................................................................................................................... Biliary T ract
FIGURE 7.3. (A–H) Congenital abnormalities of
the cystic duct. (Adapted with permission from
Schwartz SI: Principles of Surgery. New York:
McGraw-Hill, 1994:1369.)
Cystic artery
A
Right hepatic artery
Cystic artery
Gastroduodenal
artery
B
C
Right hepatic artery origin
Left hepatic artery
Right hepatic
artery
Left and right hepatic
artery origins
FIGURE 7.4. (A–E) Anomalies of the cystic artery.
Gastroduodenal artery origin
Common hepatic
artery
Gastroduodenal
artery
Right hepatic artery and
gastroduodenal artery origins
PHYSIOLOGY
GALLBLADDER
The gallbladder has absorptive, secretory, and motor
functions.
Absorption
Bilirubin metabolism and bile formation have been
described in detail in Chapter 5. Bile flows from the liver
into the extrahepatic ducts. With the choledochal sphincter contracted, bile is directed into the GB via the cystic
duct. The main functions of the GB in this regard are to
store and concentrate bile during fasting for delivery to the
202 .................................................................................................................................... Biliary T ract
CBD and to the duodenum on demand during eating. The
gallbladder’s capacity is 40 to 50ml, but the liver produces
about 600 ml of bile daily. Because of the significant
absorptive ability of the GB, biliary pressure is kept low.
The GB concentrates bile tenfold by absorbing sodium
chloride and water. The mechanism of absorption across
the GB mucosa is due to electroneutral sodium-coupled
chloride transport.
Secretion
The GB secrets mucus at about 20ml/h. In hydrops of the
GB, this colorless secretion comprises white bile.
P athophysiology ................................................................................................................................. 203
Motor Function
During fasting, the GB does not simply fill up passively,
but undergoes rhythmic contractions that exchange concentrated bile with dilute bile. During eating, however, the
GB undergoes major contraction coordinated with relaxation of the sphincter of Oddi, thus delivering into the
duodenum concentrated bile required for digestion. The
major stimulus for gallbladder contraction is the hormone
cholecystokinin (CCK), released from the duodenum by
the stimulation of fat and acid. The contractile action of
CCK on GB muscle appears to be mediated through activation of intrinsic cholinergic neurons. Other mediators
of GB contraction are cholinergic reflexes (antrocholecystic, enterocholecystic) and the intestinal peptide motilin.
Relaxation of the GB muscle is mediated through VIP and
nitric oxide.
CHOLEDOCHAL SPHINCTER OR
SPHINCTER OF ODDI
Manometric studies in humans show a 5-mm zone of
resting high pressure that is 5 to 10mm Hg greater than
CBD pressure. On top of this resting pressure, phasic,
high-pressure antegrade contractions occur (Figure 7.5).
Bile flow into the duodenum requires relaxation of the
sphincter of Oddi, which is mediated via VIP and nitric
oxide. CCK, cholinergic stimulation, and glucagon also
relax the sphincter.
FIGURE 7.5. Manometric profile of the sphincter of Oddi obtained during station pullthrough tracing
of a triple-lumen catheter. (Adapted from Feldman M, Sleisenger MH, Scharschmidt BF, eds. Schlesinger
& Fordtran’s Gastrointestinal and Liver Disease: Pathophysiology, Diagnosis, and Management, 6th ed.
Philadelphia, PA: WB Saunders, 1998:933, with permission from Elsevier Science.)
PATHOPHYSIOLOGY
GALLSTONE FORMATION
Gallstones are the most common cause of biliary tract
disease. Gallstones are composed of cholesterol, bilirubin,
and calcium. Gallstones in the West are primarily choles-
terol stones. Pigment stones are often associated with
hemolytic disease and are prevalent in areas endemic to
hemolytic anemia and malaria. The major factors involved
in gallstone formation are listed in Table 7.1.
TABLE 7.1. Factors Involved in Gallstone Formation
Cholesterol
䊏
Increased cholesterol secretion in bile (e.g., obesity)
䊏
Decreased bile salt and lecithin concentration
䊏
Genetic factors (e.g., 70% of Pima Indian women have
gallstones by age 60)
䊏
Gallbladder stasis (e.g., prolonged TPN, prolonged fasting)
䊏
Bacterial infection
䊏
Hormonal causes (e.g., estrogen therapy, pregnancy)
Pigment
䊏
Bacteria in bile (b-glucoronidase)
䊏
Bilirubin overproduction (e.g., hemolytic diseases)
䊏
Stasis (e.g., stricture of CBD)
䊏
Cirrhosis
Cholesterol Stones
Cholesterol and other lipids in the bile are not water
soluble but have to be kept solubilized to prevent them
from deposition as stone. The ingenious mechanism of
solubilization depends on transporting cholesterol in the
lipophilic core of micelles. The structure of a micelle is
shown in Figure 7.6. Bile salts and lecithin are amphoteric
and aggregate to form a lipophilic core that carries cholesterol, while their water-soluble ends are arranged
peripherally at the circumference of the micelle. The
maximal ability of the micelles to carry cholesterol is called
the critical micellar concentration (Figure 7.7). When the
critical micellar concentration is exceeded, a metastable
phase is reached at which cholesterol does not precipitate
due to vesicular phase in bile. Beyond this, cholesterol
molecules precipitate by first aggregating together and
then forming crystals. A high calcium content in the bile
favors cholesterol precipitation. Cholesterol supersaturated bile from patients with gallstones forms cholesterol
crystals more easily than that from individuals with no
gallstones. This observation suggests that other substances
(e.g., apo-AI, mucus, and other bile proteins) also play a
role in gallstone formation.
FIGURE 7.7. Tricoordinate phase diagram for determination of
cholesterol saturation index. The shaded area represents micellar
liquid in which cholesterol remains solubilized. Beyond this, cholesterol molecules precipitate to form crystals.
In addition to cholesterol saturation, other conditions
that favor gallstone formation include stasis, bacterial
infection, rate of water and electrolyte absorption, estrogen therapy, and pregnancy.
Pigment Stones
Pigment stones account for 10% to 25% of gallstones in
the U.S.
marily of calcium bilirubinate, and 50% of them are
radiopaque. The incidence of pigment stones is high in
Japan and in countries endemic to malaria and hemolytic
diseases.
pigment stones. The major event in the formation of
pigment stones is an increase in unconjugated bilirubin
in the bile. An important factor is the presence of bacteria, which deconjugate bilirubin using the enzyme b-
glucosidase, phospholipase A, and others. Pigment stones
contain bacteria or bacterial skeletons in 90% of cases.
Other factors in bile that favor deconjugation are the presence of calcium carbonate and phosphate, suggesting
defective alkalinization of bile.
1
They are black in appearance, composed pri-
1
Primary choledocholithiasis is usually due to
BILIARY COLIC
Attacks of colicky right-upper quadrant (RUQ) pain, often
radiating to the right infrascapular region, are caused by
intermittent obstruction of the cystic duct by a gallstone.
This clinical syndrome is the most common manifestation
of gallstones. The attack often follows ingestion of food,
which contracts the gallbladder and impacts a stone in the
cystic duct. The cystic duct obstruction is temporary,
lasting from a few minutes to several hours, and is roughly
coincident with the duration of pain. Presumably, the
FIGURE 7.6. Structure of a micelle. The micelle is an aggregation of bile salts and lecithin with a lypophyllic core that carries
the water-insoluble cholesterol.
204 .................................................................................................................................... Biliary T ract
stone falls back into the gallbladder, relieving the obstruction. Because no significant inflammatory process ensues,
tachycardia, fever, or leukocytosis are uncommon. Simi-
TABLE 7.2. Spectrum of Clinical Pathology in Cholecystitis
Acute Cholecystitis
Acalculous
Calculous
䊏
Nonperforated
䊏
Perforated
Localized: Pericholecystic abscess
Free: Bile peritonitis
䊏
Cholecystenteric fistula: Gallstone ileus
䊏
Empyema
䊏
Emphysematous
Chronic Cholecystitis
Uncomplicated
Mucocele
larly, jaundice or significant liver dysfunction does not
occur.
CHOLECYSTITIS
Cholecystitis or inflammation of the gallbladder has many
forms. The spectrum of clinical pathology is summarized
in Table 7.2.
Acute Calculous Cholecystitis
Acute cholecystitis usually results from a gallstone
impacted in Hartmann’s pouch, obstructing the neck of
the GB. The result is distension of the gallbladder, resulting in concentration of bile, which causes subserosal
inflammation with edema and thickening of the GB wall.
Mucosal hemorrhage and ulceration are common. The
obstructing stone and ensuing inflammation may also
cause ischemic necrosis of the neck of the GB and may
result in thrombosis of the cystic artery, leading to gangrenous cholecystitis. The process is almost always complicated by secondary bacterial infection. Transmural
necrosis may lead to perforation and pericholecystic
abscess (Figure 7.8). Free perforation and bile peritonitis
are rare but may occur in the immunocompromised
patient. Rarely, the gallstone in Hartmann’s pouch may
erode into adjacent bowel, usually the duodenum, to cause
cholecystoenteric fistula and gallstone-induced small
bowel obstruction (gallstone ileus).
The local inflammatory process is accompanied by systemic manifestations including tachycardia, fever, and
leukocytosis. Jaundice and mild liver dysfunction
occur infrequently. Hyperbilirubinemia is always mild
(<3 mg%).
Empyema of the Gallbladder
Occasionally, the GB lumen becomes filled with frank pus
(Figure 7.9). The patient becomes acutely toxic, with
spiking high fever, chills, and marked leukocytosis. Why
some patients develop empyema as a complication of
acute cholecystitis is unknown.
Acute Emphysematous Cholecystitis
This is a rare form of acute cholecystitis in which anaerobic infection of the GB develops, causing formation of gas
FIGURE 7.8. Pericholecystic abscess is manifest on x-ray as multiple air bubbles (arrows) indicating air
both within and surrounding the inflamed gallbladder. (Courtesy of Henry I. Goldberg, MD.)
P athophysiology ................................................................................................................................. 205
A
B
FIGURE 7.9. Empyema of the gallbladder. (A) The ultrasound shows complex echoes within the gallbladder caused by the presence of pus and a greatly thickened wall due to acute cholecystitis. (B) The
gross cut section of empyema demonstrates distention with pus and marked thickening of the wall.
(Courtesy of Linda D. Ferrell, M.D., and Henry I. Goldberg, MD.)
within the lumen and gallbladder wall (Figure 7.10). This
complication is more likely to occur in patients with diabetes. The anaerobic bacteria involved may be clostridia,
anaerobic streptococci, or gas-forming Escherichia coli.
Acalculous cholecystitis may also occur postoperatively,
usually immediately upon the resumption of oral feeding.
The exact pathophysiological mechanisms are unknown.
The hypotheses include hypoperfusion or ischemia of the
GB and primary bacterial invasion (Escherichia coli,
Acute Acalculous Cholecystitis
Approximately 5% of patients with acute cholecystitis have
no gallstones. This condition is frequently associated with
other major systemic insults resulting from multiple
trauma, sepsis, major burn, or multiple organ failure.
clostridia and rarely Salmonella typhi). In postoperative
patients and in those on TPN with prolonged fast, sludge
is often found within the lumen. It is possible that in these
cases of prolonged stasis, contraction of the GB leads to
obstruction of the cystic duct from accumulated sludge.
The essential features are summarized in Table 7.3.
206 .................................................................................................................................... Biliary T ract
A
B
FIGURE 7.10. Acute emphysematous cholecystitis. (A) The plain abdominal x-ray shows a large gas
bubble within the gallbladder lumen, surrounded by a linear streak of air (arrows) in the GB wall. Air
is also present in the biliary tree (large arrow). The metallic device is a dorsal column stimulator. (B)
The CT scan shows an air-fluid level in the gallbladder and air in the wall of the gallbladder (arrows).
(Courtesy of Henry I. Goldberg, MD.)
208 .................................................................................................................................... Biliary T ract
Chronic Cholecystitis
Gallstones may cause chronic inflammation of the wall of
the GB. The symptoms are chronic, intermittent, mild to
moderate pain, intolerance to fatty foods, and intermittent
nausea or vomiting. The inflammatory process involves
infiltration of the mucosa and submucosa by chronic
inflammatory cells, and the formation of crypts in the
mucosa known as Rokitansky–Aschoff sinuses.
Mucocele of the Gallbladder
Chronic obstruction of the gallbladder may sometimes
cause chronic rather than acute inflammation, with
preservation of the secretory epithelium of the GB. Over
a period of time, the lumen becomes filled with a clear or
slightly milky fluid due to the mucous secretion of the
epithelium. Mucocele of the gallbladder may attain large
size and present as a right abdominal mass.
OBSTRUCTIVE JAUNDICE
Intrahepatic obstructive jaundice was discussed in
Chapter 6. This section focuses on extrahepatic obstructive jaundice. The latter may be caused by gallstones,
tumor, or benign stricture (Table 7.4).
Most commonly, stones found in the CBD are produced in the GB and enter the CBD through the cystic
duct. Approximately 15% of patients with cholelithiasis
have stones in the CBD (choledocholithiasis). On rare
occasions, however, in conditions of prolonged stasis or
infection, stones can form primarily in the CBD. Obstruc-
tive jaundice is usually caused by a stone obstructing the
ampulla of Vater. Gallstones impacted in the neck of the
gallbladder or cystic duct can obstruct the CBD by extrinsic compression causing obstructive jaundice. This rare
phenomenon is known as Mirizzi’s syndrome.
Tumors that can cause obstructive jaundice may arise
from the CBD, the head of the pancreas or the periampullary region. Tumors of the gallbladder and metastatic neoplasm in the hilum of the liver can cause obstructive
jaundice by extrinsic compression. Benign strictures can
also cause obstructive jaundice, and may be the result of
operative injury of the CBD or sclerosing cholangitis.
Obstruction of the CBD leads to proximal dilatation.
The CBD may dilate to 1.0 to 2.5cm in diameter. The
resultant liver dysfunction typically includes conjugated
hyperbilirubinemia and elevated alkaline phosphatase,
with normal or slightly elevated levels of hepatocellular
enzymes. Longstanding obstruction of the CBD can cause
biliary cirrhosis, a process that takes many years to
develop. The more urgent and dreaded complication of
obstructive jaundice is cholangitis, sometimes referred to
as ascending cholangitis or suppurative cholangitis.
Cholangitis
Cholangitis arises from secondary infection within an
obstructed bile duct. Approximately 90% of cases are due
to choledocholithiasis. Cholangitis occurs in only 15% of
obstructions caused by a neoplasm. The bacteria most
commonly cultured from the bile are E. coli, Klebsiella
organisms, pseudomonas, Proteus organisms, enterococci,
Clostridium perfringens and Bacteroides fragilis. Anaerobes
are cultured in 15% of cases. In 1877 Charcot described a
triad of symptoms characteristic of cholangitis including
upper abdominal pain, fever with chills, and jaundice.
2
Charcot’s triad is present in about three-fourths of
patients with cholangitis. In more severe cases, known as
suppurative cholangitis, two additional clinical findings
become important: septic shock and mental obtundation.
The chills that are characteristic of suppurative cholangitis are due to septicemia and endotoxemia. Blood cultures
TABLE 7.3. Essentials: Acute Acalculous Cholecystitis
Incidence
䊏
5% of all acute cholecystitis
Clinical setting
䊏
Multiple organ failure, shock
䊏
Major trauma, major burn
䊏
TPN
䊏
Postoperative
Clinical picture
䊏
Abdominal pain in 90%–100%
䊏
Fever in 65%–70%
䊏
Leukocytosis in 85%
䊏
Abnormal liver function in 82%
Diagnosis: ultrasound
䊏
Thickened gallbladder wall (>3.5 cm)
䊏
Distended gallbladder (hydrops)
䊏
Gallbladder sludge
䊏
Submucosal edema
䊏
Pericholecystic fluid
Treatment options
䊏
Laparoscopic cholecystostomy/cystectomy
䊏
Percutaneous cholecystostomy
Abbreviation: TPN, total parenteral nutrition.
TABLE 7.4. Causes of Extrahepatic Obstructive Jaundice
Gallstones
䊏
Choledocholithiasis
䊏
Mirizzi’s syndrome
Benign strictures
䊏
Operative trauma
䊏
Sclerosing cholangitis
Neoplasms
䊏
Common bile duct cancer
䊏
Cancer of head of pancreas
䊏
Ampullary cancer
䊏
Invasive gallbladder cancer
䊏
Metastatic tumor
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