ABD GB and Bil pt 2

Biliary System and Gallbladder
- The biliary system is integral to the function of the gallbladder and is closely associated with the liver through bile ducts.
- Two primary components of the biliary tree:
- Intrahepatic Ductal System: Found within the liver; includes hepatic ducts.
- Extrahepatic Ductal System: Located outside the liver; includes the common bile duct (CBD).

Hepatic Ducts
- Comprised of a Right Hepatic Duct and a Left Hepatic Duct.
- These ducts drain the respective lobes of the liver:
- Left Hepatic Duct: Drains the left lobe of the liver.
- Right Hepatic Duct: Drains the right lobe of the liver.
- Both ducts converge to form the Common Hepatic Duct (CHD).
Three Components: The intrahepatic ducts, hepatic arteries, and portal veins are often found together, encased in an extracalaginous sheath, which can present as brighter edges or walls on imaging.
Porta Hepatis: The region where the CHD and other vessels converge, located medially and at mid-level of the liver.

The CHD travels a short distance and becomes the common bile duct (CBD).
CHD Positioning:
- Anterior to the portal vein and lateral to the hepatic artery, resembling a “Mickey Mouse” appearance on imaging.
- Right ear = Common Hepatic Duct, Left ear = Hepatic Artery.

Color Doppler
- Used to differentiate between blood flow in the vessels (such as the portal vein and hepatic artery) and bile flow in the ducts.
- Common Hepatic Duct (small and slow flow) will not demonstrate color flow, while the other vessels will.
Care must be taken to avoid misidentifying structures due to their close proximity and similar appearances in longitudinal views.

The CHD joins with the Cystic Duct from the gallbladder to form the CBD.
The CBD courses posteriorly and transitions into the duodenum, which further connects to digestive processes.

Ampulla of Vater: The junction where the CBD and the main pancreatic duct meet prior to emptying into the duodenum.
- Contains circular muscles known as the Sphincter of Oddi which regulates bile and pancreatic juice flow:
- Opens to allow bile and enzymes during digestion.
- Closes when fasting, causing bile to back up into the gallbladder for storage.
Duct of Wirsung (Main Pancreatic Duct): Carries digestive enzymes (such as amylase and lipase) from the pancreas.
- Helps in the digestion of carbohydrates, fats, and sugars.

Reservoir for bile, which is released upon hormonal stimulation, specifically cholecystokinin, after eating.
The gallbladder contracts in response to cholecystokinin to push bile through the cystic duct, into the CBD, and into the duodenum.

Observations in CT scans may include unclear findings within the gallbladder:
- Differentiating between stones, sludge, and polyps often requires ultrasound evaluation due to limitations of CT.
Important structures visible in an ultrasound include:
- Gallbladder appears hazy and hypoechoic when pathological; indicator that further investigation may be necessary.
- Right lobe of the liver, pancreas, common bile duct, and portal confluence positions must be well understood for accurate evaluations.

Common Bile Duct (CBD):
- Posterior to the pancreas head; appears circular and hypoechoic on ultrasound.
Gallbladder Identification:
- Careful scanning to ensure correct interpretation; focus on ensuring no pathology is overlooked, using gains and TGC adjustments to clarify images.
Sphincter of Oddi:
- Serves as a regulator for bile and pancreatic juices entering the duodenum, influenced by the eating state of the patient.

Bile flows through the gallbladder, cystic duct, common hepatic duct, and common bile duct, eventually merging with pancreatic enzymes at the ampulla of Vater before being released into the second part of the duodenum (C-loop).