Neck of the Gallbladder

The neck of the gallbladder is the tapered, funnel-like region that connects the gallbladder body to the cystic duct. It plays a key role in regulating bile flow from the gallbladder into the biliary tree. Despite its small size, the neck holds significant clinical importance due to its involvement in gallstone obstruction, cholecystitis, and its anatomical relationship to critical structures like Calot’s triangle. The neck contains mucosal folds known as the spiral valve of Heister, which may help maintain ductal patency or slow bile flow. Precise knowledge of the neck’s anatomy is essential during laparoscopic and open cholecystectomy to prevent biliary injury.

Structure

The neck forms the transitional zone between the gallbladder body and the cystic duct. It is curved and often bent upon itself, lying in an oblique position. The junction between the neck and cystic duct is not always sharply defined, and its configuration may vary from person to person.

Gross Morphology

• Shape: Constricted and twisted; may appear S-shaped on imaging
• Length: Approximately 1.5–2 cm
• Diameter: Narrowest part of the gallbladder, often less than 5 mm

Wall Composition

Structurally, the wall of the neck mirrors the rest of the gallbladder, though with unique internal mucosal folds:

Layer	Description
Mucosa	Columnar epithelium with prominent spiral folds (valve of Heister)
Lamina propria	Connective tissue with capillaries, lymphatics, and immune cells
Muscularis externa	Smooth muscle arranged irregularly; contracts during bile expulsion
Adventitia	Outer connective tissue layer; blends with surrounding hepatic tissue

Spiral Valve of Heister

Within the lumen of the neck and proximal cystic duct are crescent-shaped mucosal folds forming the spiral valve of Heister. These folds:

• May slow the flow of bile, preventing rapid emptying or refilling
• Possibly keep the duct patent despite external compression
• Can create challenges in endoscopic cannulation or stone extraction

Location

The neck of the gallbladder lies in a deep groove on the visceral surface of the liver, closely associated with important vascular and ductal structures. It marks the beginning of the cystic duct and sits at the apex of the gallbladder's anatomic triangle.

Topographic Relationships

• Superior: Lies under segment IV of the liver
• Medial: Bordered by the common hepatic duct
• Inferior: Continuous with the cystic duct
• Lateral: Adjacent to the gallbladder body

Calot’s Triangle

The neck is the lower boundary of Calot’s triangle (hepatobiliary triangle), which is formed by:

• Medially: Common hepatic duct
• Inferiorly: Cystic duct (originating from the neck)
• Superiorly: Inferior border of the liver

This triangle contains the cystic artery and lymph nodes and is a critical area for dissection during cholecystectomy. The neck’s proximity makes it a landmark structure in this context.

Function

Although passive in most respects, the neck of the gallbladder plays an important regulatory role in bile storage and delivery. Its architecture facilitates bile movement and contributes to pressure regulation during gallbladder filling and contraction.

Key Functional Roles

• Control of bile exit: Acts as a funnel leading bile from the gallbladder to the cystic duct
• Pressure buffer: Spiral folds may slow or modulate bile flow
• Functional valve: Prevents over-distension or rapid bile expulsion

During fasting, bile flows back into the gallbladder via the neck and cystic duct due to closure of the sphincter of Oddi. During digestion, gallbladder contraction forces bile through the neck and into the ductal system toward the duodenum.

Clinical Relevance

The neck of the gallbladder is frequently involved in gallbladder pathologies and is a key focus in imaging, surgery, and diagnostic evaluation.

1. Gallstone Impaction (Hartmann’s Pouch)

A dilated outpouching near the neck is often called Hartmann’s pouch. Stones may lodge here and compress adjacent structures:

• Mirizzi Syndrome: Compression of the common hepatic duct by a stone impacted in the neck or Hartmann’s pouch, leading to obstructive jaundice
• Cholecystitis: Obstruction at the neck leads to bile accumulation, wall edema, and inflammation

2. Surgical Landmark

The neck is the landmark used to identify and isolate the cystic duct during both laparoscopic and open cholecystectomy. Failure to distinguish the neck from the body or cystic duct can lead to complications such as:

• Misidentification of the common bile duct
• Injury to the hepatic artery or portal structures

3. Imaging and Endoscopy

• Ultrasound: Gallstones are frequently visualized lodged at the neck with acoustic shadowing
• CT/MRI: Dilated neck or Hartmann’s pouch may indicate chronic inflammation or gallbladder dysfunction
• ERCP: Difficulty cannulating cystic duct due to spiral folds or neck angulation

4. Congenital and Anatomical Variants

• High-insertion cystic duct: May obscure neck identification during surgery
• Short cystic duct: Makes dissection at the neck more challenging and risk-prone

Accurate understanding of the neck’s position and morphology is essential for safe and effective surgical and endoscopic intervention.