Gallbladder

Overview

The gallbladder is a small, pear-shaped organ that stores and concentrates bile produced by the liver. It plays an essential role in the digestive process by releasing bile into the small intestine to aid in the emulsification and absorption of dietary fats. Though not essential for life, the gallbladder significantly improves the efficiency of fat digestion.

Location

The gallbladder is located in the right upper quadrant of the abdomen. It:

• Sits on the inferior surface of the liver, in a depression called the gallbladder fossa

• Lies roughly at the level of the ninth costal cartilage near the midclavicular line

• Is in close proximity to the duodenum, transverse colon, and hepatic flexure

The gallbladder is connected to the biliary tree via the cystic duct, which joins the common hepatic duct to form the common bile duct.

Structure

The gallbladder is typically about 7–10 cm long and holds about 30–50 mL of bile when fully distended. It has three main parts:

• Fundus: The rounded, anterior portion that may project beyond the liver’s edge

• Body: The main, central region that stores bile

• Neck: The narrow part leading into the cystic duct; contains a spiral fold called the valve of Heister

Histologically, the gallbladder has:

• Mucosa: Simple columnar epithelium with microvilli, arranged in folds; lacks a muscularis mucosa and submucosa

• Muscularis externa: Smooth muscle that contracts during bile release

• Serosa/adventitia: Outer layer depending on which surface is covered by peritoneum

Function

The primary functions of the gallbladder include:

• Storage of bile: Stores bile continuously secreted by the liver during fasting periods

• Concentration of bile: Absorbs water and electrolytes to make bile more potent

• Controlled release of bile: Releases bile into the duodenum via the common bile duct in response to food intake, particularly fatty meals

Physiological Role(s)

The gallbladder supports digestive physiology in several key ways:

• Fat digestion: Bile released from the gallbladder emulsifies dietary fats, allowing pancreatic lipase to break them down

• Cholecystokinin (CCK) response: The hormone CCK is secreted by the duodenum in response to fat, triggering gallbladder contraction and sphincter of Oddi relaxation

• pH balance and waste removal: Bile helps neutralize gastric acid and eliminate bilirubin, cholesterol, and toxins

• Biliary coordination: The gallbladder ensures bile is delivered at the right time in response to meals, enhancing nutrient absorption

Clinical Significance

The gallbladder is commonly affected by various disorders:

• Cholelithiasis (gallstones): Formation of stones from bile components (cholesterol, pigment, or mixed); may be asymptomatic or cause biliary colic

• Cholecystitis: Inflammation of the gallbladder, often due to obstructed cystic duct; presents with right upper quadrant pain, fever, and positive Murphy’s sign

• Choledocholithiasis: Gallstones that migrate into the common bile duct; can cause jaundice, pancreatitis, or cholangitis

• Biliary dyskinesia: Gallbladder motility disorder resulting in improper bile release and indigestion after fatty meals

• Gallbladder cancer: Rare but aggressive; more common in patients with chronic gallstones or porcelain gallbladder

• Cholecystectomy: Surgical removal of the gallbladder; typically performed laparoscopically and does not impair long-term digestion significantly

Diagnostic tools include ultrasound (first-line for gallstones), HIDA scan for functional assessment, MRCP, and endoscopic ultrasound (EUS). Management ranges from conservative treatment to surgery based on symptoms and complications.