Fundus of the Gallbladder

The fundus of the gallbladder is the rounded, blind-ended anterior portion of the gallbladder that projects beyond the inferior border of the liver. It is the most visible and palpable part of the gallbladder, often serving as a landmark during physical examination and surgical procedures. Despite being small, the fundus is crucial in early imaging identification, gallbladder distension, and site-specific pathology. It lies close to the anterior abdominal wall and is frequently involved in inflammatory processes such as cholecystitis. Its anatomy and spatial relationships make it particularly relevant in diagnostic medicine and minimally invasive surgery.

Structure

The fundus represents the distal-most portion of the gallbladder and forms the bulbous, dome-like terminus of the organ. It tapers posteriorly into the body of the gallbladder and does not contain any exit or opening — bile does not directly pass through it but instead collects as the gallbladder fills.

Wall Composition

Like the rest of the gallbladder, the wall of the fundus consists of several histological layers:

Layer	Description
Mucosa	Simple columnar epithelium with microvilli, specialized for fluid absorption
Lamina propria	Loose connective tissue underlying the epithelium
Muscularis	Irregular smooth muscle fibers; not well-organized into layers
Perimuscular connective tissue	Fibrous layer containing vessels and nerves
Serosa (or adventitia)	Peritoneal covering (serosa) anteriorly; absent where attached to the liver (adventitia)

Shape and Size

• Shape: Rounded, dome-like end; slightly flattened in collapsed state
• Diameter: Typically 1.5–3 cm wide
• Wall thickness: Normally < 3 mm; thickens in inflammation or cancer

Location

The fundus of the gallbladder projects below the inferior border of the liver, specifically from the visceral surface, and lies in close contact with the anterior abdominal wall. Its location is clinically important due to its accessibility during palpation and laparoscopic entry.

Topographic Position

• Region: Right hypochondrium
• Landmark: Often lies at the level of the 9th costal cartilage in the midclavicular line
• Anterior: Contacts the anterior abdominal wall; visible on ultrasound
• Posterior: Continues into the body of the gallbladder
• Superior: Touches the inferior surface of the liver (in gallbladder fossa)
• Inferior: May abut the transverse colon or anterior duodenum

Due to its projection from the liver’s undersurface, the fundus is often the first portion visualized on ultrasonography, especially in fasting patients where the gallbladder is fully distended.

Function

Although the fundus does not have a distinct functional role apart from the rest of the gallbladder, it plays a passive role in bile storage, expansion, and disease presentation. It acts as a capacitive reservoir and often reflects pathological states due to its dependent location and proximity to peritoneal surfaces.

Functional Contributions

• Bile storage: The fundus accommodates volume during gallbladder filling
• Pressure accommodation: Passively distends as bile accumulates when the sphincter of Oddi is closed
• Site of stasis: Stones often lodge or sediment here, especially during prolonged fasting or gallbladder dysfunction

Relevance in Hormonal Response

When food enters the duodenum, cholecystokinin (CCK) is released, triggering contraction of the gallbladder. The fundus contributes to this contractile movement, although less effectively than the muscular body and neck. Delayed emptying of the fundus has been associated with biliary dyskinesia and stone formation.

Clinical Relevance

The fundus is involved in several diagnostic and surgical situations due to its anterior position, ability to distend, and common involvement in gallbladder disease.

1. Palpation and Murphy’s Sign

• Murphy’s Sign: Positive when palpation over the fundus during deep inspiration causes pain — a classic sign of acute cholecystitis
• In thin individuals, the fundus may be palpable below the costal margin during right upper quadrant examination

2. Gallbladder Pathologies Affecting the Fundus

• Cholelithiasis: Bile stasis often begins in the fundus; stones frequently accumulate here
• Acute cholecystitis: The fundus is the first area to become edematous or necrotic
• Gallbladder carcinoma: Often begins in the fundus due to chronic irritation by gallstones
• Porcelain gallbladder: Calcification typically begins in the fundus wall

3. Imaging and Ultrasound

The fundus is the most consistently visualized part of the gallbladder on ultrasonography, particularly in the fasting state when bile fills the gallbladder:

• Appears as an anechoic (black) structure with a thin, echogenic wall
• Wall thickening or pericholecystic fluid near the fundus indicates cholecystitis
• Non-shadowing echogenic material in the fundus may represent sludge

4. Surgical Considerations

• Laparoscopic cholecystectomy: The fundus is grasped and retracted superiorly to expose Calot’s triangle and identify the cystic duct and artery
• Open surgery: Fundus-first dissection may be used in cases of severe inflammation where Calot’s triangle is not safely accessible

Understanding the anatomy and landmarks of the fundus helps avoid misidentification and injury to nearby structures such as the colon, duodenum, and hepatic flexure.