The following video will go through Normal abdominal anatomy on CT imaging. We'll go through the different planes that you see this anatomy on. And we'll talk about what a non-contrast CT looks like compared to a contrast CT scan. And with a contrast CT scan will appreciate different appearances of the organs based on the timing of the contrast ministered. The following are three CT scans that the abdomen performed both with and without intravenous contrast. The image to the left most of your screen is performed without intravenous contrast while the images to the middle and to the right of the screen are the ones reformed with intravenous contrast. To see contrast has been given, we can look at the heart on the image with no contrast given the heart has a relatively grey appearance. With contrast the heart gets brighter as the intravenous contrast is taken up by the heart itself. The difference between the middle image and the right image is the face in which the image was taken. The middle image has performed approximately 30 seconds after giving intravenous contrast, so most of the contrast is in the arteries. Well, image to the right of the screen was performed in a portal venous phase approximately 70 seconds after giving intravenous contrast. So you have some contrast in the arteries and a lot more contrast in the portal veins. Before showcasing the anatomy, I want to scroll through these three images, so you can get an appreciation of what the different organs look like both with and without intravenous contrast. So as we scroll through the different organs, we can see that without intravenous contrast the aorta appears grey in color, with intravenous contrast the aorta is much brighter, in the arterial phase, that is the middle image because most of the contrast is in the aorta. The aorta appears very bright as to the arteries that come off the aorta. On the portal venous phase, the aorta does appear bright but you see more contrast within the venous system. For example here, in the portal vein and here in the IVC or inferior vena cava. So I'll just scroll through these images so you get an appreciation of what the different organs look like without contrast and then with contrast, what they look like in an arterial phase and portal venous phase. In general, intravenous contrast is very useful for evaluating most conditions of the abdomen. Non-contrast CT scans are very useful to look for stones in the kidneys or other organs, to look for hematomas. They're also useful if you want to see whether a mass and any of the organs enhances with the non-contrast CT scan serving as a baseline upon, which you can either subjectively or objectively quantify the amount of enhancement that a mass may or may not have. I'll now move on to showcasing how the different organs look like on a CT scan of the abdomen? Firstly, I'd like to orient everybody to have the patient as positioned. This semi linear shape at the bottom air is the CT gantry and it's what the patient is lying down as they entered the CT scanner. So this area over here is going to be posterior to the patient, opposite area here is obviously going to be anterior, over here by conventional be the right side of the patient and here will be the left side of the patient. As we scroll through these images, we're going to be strolling quarterly that is towards the feet of the patient. As we do this, the first organ I'd like to showcase to you is the spleen. We can see the spleen over here, in the left upper quadrant. On this image we can also see a portion of the left adrenal gland, the aorta, the inferior venacava as well as portion of the liver, over here is the stomach. So a continuous scroll downwards to get you full extent with the spleen looks like. And I'm going to scroll upwards again. The next organ I'd like to showcase to you is the left adrenal gland. We can see it nicely over here and it has this kind of triangular shape. And we'll see that again on the coronal slices, you can appreciate the triangular shape nicer in the coronal slices. On this image, we can also see a portion, the right adrenal gland over here. As scroll downwards, we can see the left kidney and the right kidney. So we can scroll all the way down to get the full extent and back up again, to see what the kidneys look like in the actual plane. And then we can also see the pancreas. Its the pancreatic tail as it about a portion of the spleen, pancreatic body, the pancreatic neck. As we go down, we can see the pancreatic head and the sharp almost triangular shaped structure is the pancreatic uncinatus process. So I'm going to scroll all the way through that TV and extent of what that looks like? Now, on the right up quadrant, we can see this sort of oval shaped structure here. It's a little bit under distended but that's going to be the patient's gallbladder and of course, surrounding the gallbladder is going to be the liver. So we're going to scroll up, and see the liver, and down again, see the liver dome over here. And we can see this whole structure over here is going to be the liver. The multiple vessels running through it. In some of these vessels I'll point out to you, over here it's going to be the main portal vein goes into the liver and splits up into the right portal vein. And the left portal vein, it have multiple structures coming from the liver draining into the inferior venacava that's going to be the left hepatic vein, middle hepatic vein and right hepatic vein. This person happens to have an accessory hepatic vein that's coming from the right hepatic lobe training also directly into the inferior venacava over here. As mentioned previously, this structure here is going to be the stomach. As we scroll down, we can see a different portion of the stomach, the distal aspect of it. And as we go down over here, we're going to see the duodenum. The duodenum comes across goes from the right side of the patient to the left side of the patient at which point around here as a cross of the midline it's going to become the duodenum. Other structures that we can see, the structure over here, is going to be the descending colon. We can follow that all the way upwards to the splenic flexure, where it meets the transverse colon. Can see portions of the transverse colon as it goes across. Going upwards now to the hepatic flexure near the liver. And again, downwards over here, this is the ascending colon. I'll also showcase some muscles, so everyone is aware where they are. Over here is the slowest muscle on the right side and on the left side. And just posterior to it lying almost horizontally is the quadratic small-bore muscle. Also in these image you can see these three muscles of the inter abdominal wall. The outermost muscles is the external oblique muscle. The next one is the internal oblique muscle while the last one is the transverse abdominis muscle. In the midline you can see the rectus abdominis muscle meeting centrally at a person called the linea alba. I'll now showcase some of the arteries and this is best seen on the arterial face of this exam performed at about 30 seconds after giving intravenous contrast. So the first big aorta of course, we see is the descending aorta. As it comes into the abdominal cavity and becomes the abdominal aorta, right about here. And the first pressure that gives off is the celiac artery. Celiac artery breaks off into the common hepatic artery and the splenic artery over here. We can follow the Splenic artery and see how it nicely goes all the way to the spleen. There's an additional branch that comes off over here, and that's called the left gastric artery and that runs in the gastro hepatic ligament. This fatty ligament you can see over here. The next main branch of the aorta is the superior mesenteric artery, we can see it coming of over here. And this gives rise to multiple branches that profuse the small bowel as well as the majority of the colon. We can also see the right renal artery coming off at a similar level. And the left renal artery coming off just a little bit lower. The last major branch off the aorta is the inferior mesenteric artery. And that gives perfusion to the remaining distal portions of the colon as well as organs in the pelvis. So now, showcase some of the same anatomy that we've discussed but in the coronal plane. And so, just to orient everybody before we go through the images and the coronal plane, up here is the head of the patient, down here its towards the feet of the patient. And this side is the right side, this side is the left side. And we're going to start by scrolling from posterior to anterior and you know your posterior because you can see the lumbar spine and thoracic spine retevor body's coming into the image. So as we scroll from posterior to anterior, one of the first organs you're going to see is the spleen, that is in the left upper quadrant, you can see it's craniocaudal extent and this plane very nicely. Adjacent to it on this image you can see, the left kidney. Now, on the other side of the spine you can see a portion of the right kidney as well as the liver that lives right above the kidney over here. As you scroll through these images, we can start to see the adrenal glands also coming into the picture. This triangular shaped structure that lives on top of the left kidney on the left side and on top of the right kidney on the right side over here. On this image, we can also see some of the muscles that we talked about specifically the slowest muscles extend down to the pelvis. And now, as we scroll through these sets of images we can start to see portions of the pancreas, this is the pancreatic tail. And if we focus on that we're going to see the body come into the picture. Pancreatic neck over here and that dives a little bit downwards to form the pancreatic head and the ants in that process over here. The gallbladder in this patient is relatively decompressed and we can see a little bit over here adjacent to the liver. This of course, is the liver itself. As we scroll now more anteriorly we can see some of the hepatic veins coming in into the IVC, the inferior venacava. We can also see adjacent to the inferior venacava is of course, the abdominal aorta appears the stomach. Can TV Gastroesophageal junction in this location. This is the funds of the stomach. As we scroll more anteriorly, we're going to get to the gastric body over here. The gastric and trim over here. Gastric pylorus that meets up with the duodenum, which runs downwards and goes across the midline over here, to form the duodenum starting just as it crosses the midline. We can also see some of the large bowel in this image. Over here is the ascending colon. At around this area is going to be the hepatic flexure, that point this becomes the transverse colon. You can see the transverse colon very nicely going all the way across the midline. And up again, in the left upper quadrant, we're now it's the splenic flexure specifically that'll be around this location. And then we come downwards again, you can see the descending colon. On this image over here, you can see the main portal vein putting up into the right portal vein and the left portal vein. This is the splenic vein that joint drains into the main portal vein and you can see it coming from the spleen. And this is the superior mesenteric vein. This structure over here, which trains the small bowel and the majority of the colon that drains into the main portal vein over here. To review some of the arterial anatomy in the coronal plane. We'll go back to our arterial phase images, as you scroll from posterior to anterior., remember as you see the spine that's more posterior. It's just former anterior can start to see the abdominal aorta. First branch that comes off the abdominal where is the celiac artery that gives rise to several branches one of which is the left gastric artery going cephalate. The common hepatic artery going to the right and the splenic artery, a portion of which you can see here going to the spleen. The next big branch of the aorta is the super mesenteric artery, which is going to be this branch over here that supplies the small bowel and the majority of the large bowel. And the last branch of course, the smaller artery, which is the inferior mesenteric artery that you can see coming off over here. On this image, we can also see the right renal artery going to the kidney and the left renal artery arising a little bit more inferior to it going to the left kidney.
