Gallbladder Anatomy
The gallbladder is a pear-shaped organ located in the gallbladder fossa on the inferior surface of the liver, typically positioned immediately posterior to the inferior margin of the liver in the mid-clavicular line, though its location, size, shape, and axis are highly variable. 1
Anatomical Location and Variability
The gallbladder demonstrates significant anatomical variation in clinical practice:
- Position: The gallbladder may lie anywhere between the midline and the midaxillary line 1
- Fundus location: In some patients, the fundus extends several centimeters below the costal margin; in others, the gallbladder sits high in the hepatic hilum, almost completely surrounded by hepatic parenchyma 1
- Relationship to liver: The gallbladder is typically embedded in a fossa on the inferior surface of the liver, with the fundus often remaining attached to the liver via the cystic artery 2, 3
Structural Components
The gallbladder consists of three main anatomical regions:
- Fundus: The rounded distal end, conventionally displayed on the right side of ultrasound images 1
- Body: The main storage portion
- Neck: The proximal portion that connects to the cystic duct, conventionally displayed on the left side of ultrasound images 1
The gallbladder may contain internal folds and septations, which represent normal anatomical variants 1
The Hepatocystic Triangle
The hepatocystic triangle is a critical anatomical landmark composed of the cystic duct, common bile duct, and liver. 1 This triangle is essential for surgical identification during cholecystectomy and represents a key safety landmark.
The critical view of safety (CVS) requires visualization of three key elements 1:
- The hepatocystic triangle with no exposure of the common bile duct
- The lower part of the gallbladder separated from the liver bed
- Only two structures entering the gallbladder: the cystic duct and cystic artery
Associated Ductal and Vascular Anatomy
The cystic duct connects the gallbladder neck to the common bile duct and may vary significantly in length and course. 1
Key anatomical relationships include:
- Common bile duct (CBD): Located in the porta hepatis, typically anterior and lateral to the portal vein 1
- Cystic artery: Supplies the gallbladder and is often embedded in the liver parenchyma 3
- Portal vein: A reliable landmark for locating the CBD, which it accompanies in the porta hepatis 1
- Main lobar fissure: A linear echo connecting the gallbladder to the right or main portal vein, visible on ultrasound in approximately 68% of patients 4
Anatomical Variants and Clinical Pitfalls
Several anatomical variations can complicate diagnosis and surgical procedures:
- Intrahepatic gallbladder: The gallbladder may be deeply embedded within liver parenchyma 2, 3
- Double-pouched or sigmoid gallbladder: Rare folding variations that can create diagnostic confusion on imaging 5
- Short cystic duct: May increase surgical risk during cholecystectomy 1
- Anomalous arterial anatomy: A second cystic artery or large artery posterior to the cystic duct may be present 1
The highly variable anatomy of the gallbladder necessitates systematic real-time scanning in at least two orthogonal directions to avoid confusing it with other fluid-filled tubular structures. 1
Functional Anatomy
The primary function of the gallbladder is to store and concentrate bile, which aids in fat digestion 2. The gallbladder contracts in response to cholecystokinin (CCK) released after food intake, representing normal physiological function 6.