 So, our first case is a 20-year-old female. The history provided is billory obstruction suspected, and for that, the ordering providers ordered an MRI of the abdomen without intravenous contrast, and I wanted to showcase this case to simply go through some normal gallbladder anatomy. And over the course of this master course, I'm going to show you about 30 odd cases, and I have to tell you, the one that was the most difficult to find cases for was the normal gallbladder, because there are so many little variants within the gallbladder, and it's challenging to get a gallbladder that looks distended enough, but not too distended in order to showcase the normal anatomy. But this is a pretty good representation of the normal gallbladder. The sequence over here is a T2-weighted axial image. Over here, we have T2-weighted coronal image. Both of them are non-fat saturated. And as you scroll downwards, you can see the liver over here, and as we scroll just inferiorly, tucked away here is the gallbladder. Sort of an oval, or some people describe it as a pear-shaped structure. It's located along the undersurface of the liver. That sort of anatomic relationship is perhaps better appreciated on the coronal images, where you can see the gallbladder over here. Again, oval shapes, pear-shaped, it's also been described. And I'm not one to remember sizes of organs. I think it can get kind of confusing, but if you're somebody who likes to remember sizes, in general, gallbladder length can measure up to seven centimeters. Gallbladder transfers dimension up to four centimeters. And in my experience, that transfers dimension becomes more important. Once it gets more than four centimeters, we start to think about gallbladder distension. Now, the gallbladder itself can be split into different portions. As we can see over here on this 3D coronal MRCP image, this is mipped, so you have a very thick slab showcasing the gallbladder all at once. We can see over here, this is the funness of the gallbladder. That's followed by the body of the gallbladder. As it starts to taper, this is known as the infundibular portion of the gallbladder. That leads into the neck of the gallbladder right over here. And finally, you have the cystic duct that extends outwards from the neck of the gallbladder, which then meets the common hepatic duct. I'm going to zoom in on the cystic duct for a second. You can see as you look at the cystic duct, if you were to take your finger and just run across it, it has this undulating appearance going up and down, up and down. It looks quite different from any of the other surfaces of the gallbladder and any of the bile ducts. And that appearance is caused by what is known as the spiral valves of heister. These are concentric mucosal bands located along the endoluminal surface of the cystic duct, so that appearance is quite normal. And you'll see that from time to time within the gallbladder. You can see on the T2-weighted imaging, generally the gallbladder is T2-hyper intense, pretty homogeneous in its appearance. On the T1-weighted images that I'm showing you here is the T1-weighted image with fat saturation, the gallbladder will be generally hypo intense. But there is variability within this. Certainly if patients are fasting, have an even for a few hours, some of the water on the gallbladder is reabsorbed, the bile gets concentrated. And as a result, on the T1-weighted sequences, you may see more hyper intense signal or it may be more iso intense signal. On the T2-weighted images, you'll see more relative hypo intense signal. And sometimes you'll have a layering of that hyper intense signal layer sort of on the depended portions. And we'll see examples of that on the next few images. And it's important to remember that when you have that sort of concentrated appearance of the bile, it is challenging to differentiate that from sludge. So oftentimes I'll say concentrated bile sludge is seen in the gallbladder. If I need to make reference to it. So there you have it. This is the normal appearance of the gallbladder with all its different parts. The normal appearance of the cystic duct in this patient who is presenting a biliary obstruction.