Fatty Meal Consumed
A fatty meal reaches the small intestine and triggers hormone release.
- Set by slider: Meal fat content (trigger strength)
- CCK: I-cell hormone (released from duodenal mucosa)
- ~5 min: CCK plasma half-life (rapid clearance)
- 15–60 min: Onset to symptoms (after eating)
Fat sensing in the duodenum
Fatty acids trigger I-cells to release cholecystokinin into blood.
Meal composition matters
Higher fat content produces a stronger, longer hormone surge.
Individual trigger threshold
Some patients react to even modest amounts of dietary fat.
CCK Stimulates Gallbladder Contraction
Cholecystokinin travels through blood and binds gallbladder smooth muscle receptors.
- CCK1R: CCK receptor type (smooth muscle target)
- ~10 min: Signal transit time (blood to gallbladder)
- Relaxes: Sphincter of Oddi (allows bile to flow out)
- Dose-dependent: Contraction trigger (scales with CCK level)
CCK receptor binding
CCK binds CCK1R receptors on gallbladder smooth muscle cells.
Coordinated motor response
Gallbladder contracts while the sphincter of Oddi relaxes.
Neural reinforcement
Vagal nerve activity further amplifies the contraction signal.
Gallbladder Contracts and Bile Moves
Smooth muscle squeezes stored bile toward the narrow cystic duct.
- 50–75%: Normal ejection fraction (healthy gallbladder emptying)
- ~1–3 mm: Cystic duct diameter (narrowest bile pathway)
- 30–60 min: Contraction duration (per meal response)
- 30–50 mL: Bile volume stored (typical fasting gallbladder)
Wall muscle shortens
Circular smooth muscle fibers shorten, raising internal pressure.
Bile pushed toward the neck
Fluid concentrates and flows toward the cystic duct opening.
Pressure rises against resistance
A narrow duct means pressure builds faster than outflow.
Gallstone Obstructs the Cystic Duct
A stone lodges in the duct, blocking bile from escaping.
- ~10–15%: Gallstone prevalence (adults, mostly asymptomatic)
- ~80%: Cholesterol stone share (of all gallstones)
- Transient: Obstruction type (stone often dislodges later)
- Stone ≥ duct: Critical size ratio (triggers blockage)
Size relative to duct matters
Obstruction occurs only when the stone exceeds duct width.
Bile has nowhere to go
Trapped bile raises pressure inside the contracting gallbladder.
Often self-resolving
The stone frequently dislodges back into the gallbladder lumen.
Biliary Colic Pain Peaks
Stretched gallbladder walls fire pain signals felt under the ribs.
- RUQ / epigastric: Typical pain location (right upper quadrant)
- 30 min–6 hrs: Episode duration (classic biliary colic)
- Right shoulder blade: Referred pain site (via phrenic nerve)
- Stone dislodges: Resolution (pain subsides gradually)
Wall tension drives pain
Stretch receptors in the gallbladder wall signal visceral pain.
Colicky, waxing pattern
Pain rises and falls as the gallbladder keeps contracting.
Radiates to the back
Pain often refers to the right shoulder or scapula.