Expansion
Cholecystokinin contracts the gallbladder and relaxes the sphincter
Expansion
Between meals
- The sphincter of Oddi is closed
- Bile is diverted into the gallbladder, where it is concentrated up to tenfold by absorption of water and electrolytes
After a meal, particularly a fatty one
- Cholecystokinin is released from duodenal I cells
- It causes gallbladder contraction and simultaneous relaxation of the sphincter of Oddi
- Vagal stimulation contributes
- Bile enters the duodenum
The gallbladder empties over 30 to 60 minutes and refills between meals.
Clinical points:
- Opioids, particularly morphine, cause sphincter of Oddi spasm, raising biliary pressure and potentially worsening biliary colic and pancreatitis
- Cholecystokinin analogues are used in HIDA scanning to assess gallbladder ejection fraction
- After cholecystectomy the reservoir is lost, so bile flows continuously; most patients adapt, but some develop bile salt diarrhoea
- Sphincter of Oddi dysfunction causes post-cholecystectomy biliary type pain