The anatomy of an ERCP

A few of my students have expressed interest in learning more about the basics of an ERCP so they know what they're looking at while observing one. They are really quite simple for the technologist to perform, but there is a lot going on during them that you need to be aware of (for any other reason than to know what is expected of you during the procedure).

First, you need to know your basic anatomy.



Before you begin any fluoroscopy, the G.I. doctor will have the patient in an LAO position (usually) and under conscious sedation, will feed the endoscope into the mouth, down the esophagus, through the stomach, ultimately to visualize the duodenum. The video monitor that the GI team brings with them will display the region around the c-loop of the duodenum in hopes to visualize the ampilla - where the common bile duct empties into the duodenum.

The purpose of this exam (at least diagnostically) is to obtain an angiogram of the CBD and connecting vessels, or a cholangiogram. As we know, an angiogram cannot be done on specific vasculature without a selective catheter. The whole reason we use the endoscope is so that we don't have to surgically go in and dilate the CBD with a catheter and guidewire. We can do it with minimal invasion of the body as a same-day procedure.

So as you're watching the GI team's video monitor, they will be searching for the ampilla, and attempting to dilate it with a catheter and guidewire. In some cases, it is easy to spot because there will be bile spewing from it. You should look for a curve in the bowel with an elevated mound around the corner - this should be the ampilla.



The picture on the left is the pre-dilated ampilla, and on the right there is a catheter that is already placed in the CBD.

Now comes our part... the endoscope is too large to fit inside the CBD, so we must rely on fluoroscopy to visualize the hepatic vasculature. Once the ampilla is dilated, a guidewire and catheter are usually inserted. Fluoroscopic guidance is needed to assist in proper placement of the guidewire and catheter, and a diagnostic angiogram should be performed. The doctor will inject contrast to see if there are any stones, strictures, or any other abnormalities.





Once a diagnostic angiogram is performed, an interventional portion of the procedure can be performed based on the findings. If there are stones, they can be retrieved with a balloon or a basket, a stent can be placed or removed, or angioplasty can be done (widening of the vessel with a balloon). Keep your eyes open for new treatments on the market utilizing new technologies and selective devices.