Biliary System Resin Casting: A Technique for Analyzing 3D Architecture of Biliary System in Murine Model Using Radiopaque Resin Injection

Before injecting resin into the biliary system of the mouse, start moving the intestine and pancreas to the left side of the mouse using a cotton swab, wetted with PBS, to expose the common bile duct and portal vein. Then, make a small transversal incision in the inferior vena cava. Flip the ventral side of the liver towards the heart to expose the visceral surface and the hilar region, and locate the common bile duct that runs from the hilar region across the pancreas, and into the intestine at the sphincter of Oddi. Use the straight forceps to clear the surrounding tissue area of approximately 5 millimeters from the common bile duct.

Then, by placing a silk suture thread under the common bile duct, tie a loose overhand knot around the common bile duct. Hold the spring scissors flat against the common bile duct to make an oblique incision to the common bile duct at the spot where the common bile duct enters the pancreas and intestine, next to the sphincter of Oddi. Next, mix 1 milliliter of the yellow resin with 50 microliters of the MV curing agent, and fill a 1 milliliter Luer syringe with the resin-curing agent mixture.

Connect the filled syringe with the tubing set #1 and press the plunger to fill the tubing till the resin-curing agent mixture drips from the tip of the tubing. Use the forceps to straighten the area around the common bile duct incision, before inserting the tubing into the opening in the common bile duct, with the longest edge of the beveled tip downwards towards the dorsal side of the bile duct. Then, tighten the silk thread knot to secure the tubing inside the common bile duct.

After injecting the resin into the common bile duct, observe the gallbladder and the individual liver lobes. Massage the liver with a PBS-wetted cotton swab to help spread the resin equally. Resin-filled bile ducts' terminal branches will be faintly visible at the liver surface. Stop injecting the resin when dots of resin appear at the surface of the liver, or when resistance is met. Then, remove the tubing by pulling out of the common bile duct, and quickly tighten the silk knot using forceps to prevent the resin from leaking out.