Gallbladder Anatomy

The gallbladder is a piriform (pear-shaped) organ that straddles the undersurface of segments IVB and V of the liver. It has an inferior peritoneal surface and a superior hepatic surface that is closely applied to the gallbladder bed in the liver. The cystic plate is a condensation of fibro-areolar tissue that separates the gallbladder from the liver parenchyma. Small bile ducts may drain from liver parenchyma to the gallbladder through the cystic plate (ducts of Luschka); this may result in bile leak and collection, even without an apparent bile duct injury, during cholecystectomy. The part of the gallbladder projecting beyond the undersurface of the liver is called the fundus, which continues into the main body of the gallbladder, which lies in a fossa on the undersurface of the liver. On computed tomography, the gallbladder neck is seen in higher cuts (sections) than the gallbladder body, which is seen higher than the gallbladder fundus.

The body of the gallbladder narrows into an infundibulum, which leads through the neck to the cystic duct. The cystic duct has spiral folds of mucosa called “valves” of Heister that may prevent insertion of a catheter through the cystic duct into the common bile duct during an intraoperative cholangiogram. An inferior sacculation (outpouching) of the gallbladder infundibulum or neck is sometimes present; this is called the Hartmann pouch. The Calot’s triangle is bounded by the cystic duct on the right, common hepatic duct (CHD) on the left, and undersurface of the liver above; the cystic artery and cystic lymph node lie in the Calot triangle. A peritoneal cholecystoduodenal fold connects the gallbladder neck to the first part of the duodenum.

The lesser omentum runs from the inferior surface of the liver (between the porta hepatis and the umbilical fissure) to the lesser curvature of the stomach and the first part of the duodenum. The free right edge of the lesser omentum is called the hepatoduodenal ligament (HDL). The omental (epiploic) foramen (of Winslow) behind the HDL leads to the lesser sac (omental bursa).

The right and left hepatic ducts join outside the liver in its hilum (porta hepatis) to form the common hepatic duct (CHD). The cystic duct joins the CHD to form the common bile duct (CBD), which travels downward in the HDL along with the hepatic artery to its right and the portal vein behind it. The upper limit of the diameter of the normal CBD is 6-7 mm.

The CBD has supraduodenal, retroduodenal (behind the first part of the duodenum), infra-/intraduodenal or retropancreatic (in a groove or sulcus behind or a tunnel through the upper half of the head of the pancreas), and intraduodenal (intramural) parts.

The terminal part of the CBD is joined by the terminal part of the pancreatic duct in the pancreatic head to form a common channel (called the hepatopancreatic ampulla when dilated), which runs through the medial duodenal wall and opens on the dome of the greater duodenal papilla, a nipplelike projection on the medial wall of the middle segment of the second part (C loop) of the duodenum. Both ampulla and papilla are eponymously related to Vater.

The gallbladder has the following components: mucosa composed of columnar epithelium that secretes mucus (not bile, which is produced in the liver and is only stored and concentrated in the gallbladder), tunica (lamina) propria, muscularis propria (crisscrossing muscles), subserosa (connective tissue), and serosa (on the inferior surface only, not on the superior hepatic surface). The gallbladder has no submucosa. The inner mucosal surface of the gallbladder has multiple polygonal compartments, giving it a honeycomb appearance.

Rokitansky-Aschoff sinuses are mucosal outpouchings that go through the muscularis propria into the perimuscular/subserosal tissue. The cystic duct has spiral folds of mucosa (called valves of Heister) that may hinder its cannulation for intraoperative cholangiography. The common bile duct (CBD) has a fibroelastic wall with no muscle layer except for the submucosal sphincter (of Boyden) around its lower end; it is lined with columnar epithelium, which secretes mucus (this mucus is the ‘white’ bile present in the CBD in patients with surgical obstructive jaundice SOJ).

The gallbladder is a reservoir; its size, therefore, changes from time to time depending on the volume of its contents (bile or mucus). A normal gallbladder has a capacity of 30-50 mL but is immensely distensible; an obstructed gallbladder can expand to several times its normal size. If the cystic duct is blocked by a stone or tumor, the gallbladder distends with mucus (not bile) and is called mucocele; in case of a blockage at the lower end of the CBD, for example in pancreatic cancer, the gallbladder distends with bile.

A great variety of biliovascular anomalies may occur, rendering the bile ducts vulnerable to iatrogenic injury during cholecystectomy. Examples include the following:

• Absent gallbladder (agenesis)
• A double gallbladder with 1 (common) or 2 (separate) cystic ducts
• A phrygian cap (an intraserosal fold in the gallbladder fundus)
• An aberrant cystic duct – The cystic duct can be of variable length, or no cystic duct may exist and the gallbladder neck may join the common hepatic duct (CHD) directly (sessile gallbladder); the cystic duct may join the CHD high up, or it may even join the right hepatic duct; it may have a low insertion in the common bile duct (CBD), even spiraling around and opening on the left side of the CBD
• A cholecystohepatic duct that drains from the gallbladder to an intrahepatic bile duct in the liver – If it is not recognized and ligated/clipped during cholecystectomy, it may result in postoperative bile leak and collection
• A gallbladder that has a mesentery (which is liable to torsion but makes cholecystectomy easy) ora gallbladder that is intrahepatic (which makes cholecystectomy difficult)
• An accessory right hepatic, sectoral (posterior), or segmental (V) duct that joins the CHD or even the cystic duct; this is liable to injury during cholecystectomy because it lies in Calot’s triangle
• A tortuous right hepatic artery that runs in front of the CBD (caterpillar turn or Moynihan hump); this is liable to injury during cholecystectomy
• A cystic artery that arises from the right hepatic artery to the left of the CBD and may run anterior to the CBD
• Congenital dilatation of the CBD (choledochal cyst)
• A CBD and a main pancreatic duct that do not unite to form a common channel and that open separately on the major duodenal papilla or a long (>15 mm) common channel of the CBD and pancreatic duct

In patients with chronic cholecystitis, the Calot triangle may become fibrosed and obliterated, making dissection difficult. A large stone in the gallbladder infundibulum, neck, or Hartmann pouch may compress the CBD from outside to cause biliary obstruction (Mirizzi syndrome). In later stages, an inflamed Hartmann pouch may become adherent to and may even fistulate into the CBD (cholecysto-choledochal fistula) or the duodenum (cholecysto-duodenal fistula).Small stones in the gallbladder can pass through a wide cystic duct into the CBD and ampulla and cause acute cholangitis and acute pancreatitis.

The site of maximum tenderness in acute cholecystitis is the area where the fundus of the gallbladder touches the anterior abdominal wall at the intersection of the ninth costal cartilage and the lateral border of the right rectus muscle.

The Calot triangle is the sanctum sanctorum of cholecystectomy. During cholecystectomy, the Calot triangle is dissected first, followed by dissection of the gallbladder from its bed in the liver (retrograde or classic method); sometimes, the fundus is dissected first and then the surgeon moves towards the body and neck to reach the Calot triangle in the end (antegrade or fundus first method)

In case of bleeding from the liver during surgery, an index finger may be placed in the omental foramen (of Winslow) and a thumb in front of the hepatoduodenal ligament (HDL), or a vascular or soft noncrushing intestinal clamp may be applied across the HDL to compress the hepatic artery and the portal vein.