The following video will cover a normal CT abdominal anatomy. We have a couple of objectives. At the end of this presentation the learner will be able to; identify the normal appearance of a variety of organs within the abdominal cavity, specifically the spleen, adrenal glands, kidneys, gallbladder, pancreas, liver, stomach, duodenum and portions of the colon. You'll also be able to identify the following venous structures; the inferior vena cava or IVC, hepatic veins, portal vein, and splenic vein. Finally, you'll be able to identify the following arteries; aorta, the celiac artery, common hepatic artery, splenic artery, the left gastric artery, the superior mesenteric artery, the renal artery, and last but not least the inferior mesenteric artery. Firstly, I'd like to orient everybody to how the patient is positioned. This semi-lunar shape at the bottom here, is the CT gantry and it's what the patient is lying down as they enter the CT scanner. This area over here is going to be posterior to the patient, opposite area here is obviously going to be anterior, over here by convention will be the right side of the patient, and here will be the left side of the patient. There are two additional things I'd like to point out before we go through the organs. Firstly, most abdominal CT scans, including the one shown here, are performed at about 70 seconds after giving intravenous contrast. But it's important to appreciate that sometimes we image earlier if we're interested in the arteries, and sometimes a little bit later if we're interested in certain specific pathology. Secondly, whereas this is a CT scan of the abdomen, it's important to realize though we also include a portion of the lung bases and within the heart, because in doing so we make sure that we image the entire superior most aspect of the abdominal organs. As we scroll through these images, we're going to be scrolling caudally, 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 a left adrenal gland, the aorta, the inferior vena cava as well as portion of the liver. Over here, is the stomach. I'll continue to scroll downwards to get you a full extent of what the spleen looks like. I'm going to scroll upwards again. The next organ I'd like to showcase to you is the left adrenal gland, and we can see it nicely over here and it has this triangular shape. We'll see that again on the coronal slices, you can appreciate that triangular shape nicer on the coronal slices. On this image we can also see a portion of the right adrenal gland over here. As we scroll downwards, we can see the left kidney and the right kidney. We can scroll all the way down to get the full extent and backup again to see what the kidneys look like in the axial plane, and then we can also see the pancreas. Just the pancreatic tail as it abuts 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 uncinate process. I'm going to scroll all the way through that to give you an extent of what that looks like. Now, in the right upper quadrant we can see this oval-shaped structure here. It's a little bit under the standard but that's going to be the patient's gallbladder. 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. You see the liver down over here, and we can see this whole structure over here is going to be the liver with multiple vessels running through it. Some of these vessels I'll point out to you over here is going to be the main portal vein, goes into the liver and splits up into the right portal vein and the left portal vein. If you have multiple structures coming from the liver draining into the inferior vena cava, that's going to be the left hepatic vein, middle hepatic vein and the right hepatic vein. This person happens to have an accessory hepatic vein that's coming from the right hepatic lobe draining also directly into the inferior vena cava over here. As I mentioned previously, this structure here is going to be the stomach. As we scroll down we can see 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, and which point around here as it crosses the mid line it's going to become the duodenum. Other structures that we can see, this 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. You 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 to everyone's wherever they are. Over here is the psoas muscle on the right side and on the left side. Just posterior to it lying almost horizontally is the quadratus lumborum muscle. Also in this image you can see these three muscles of the anterior abdominal wall, the outermost muscles, 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 portion called the linea alba. I'll now showcase some of the arteries and this is best seen on the arterial phase of this exam performed at about 30 seconds after giving intravenous contrast. The first big artery of course we see is the descending aorta. As it comes into the abdominal cavity it becomes the abdominal aorta, right about here. The first branch that it gives off is the celiac artery. Celiac artery breaks off into the common hepatic artery and the splenic artery over here. You 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 off the aorta is the superior mesenteric artery, we can see coming off over here. This gives rise to multiple branches that perfuse 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. That gives profusion to the remaining distal portions of the colon as well as organs in the pelvis. Now, I showcase some of the same anatomy that we've discussed but in the coronal plane. Just to orient everybody before we go through the images, in the coronal plane, up here is the head of the patient, down here is towards the feet of the patient, and this side is the right side, this side is the left side. We're going to start by scrolling from posterior to anterior. You know your posterior because you can see the lumbar spine and thoracic spine vertebral bodies coming into the image. As we scroll from posterior to anterior, one of the first organ you're going to see is the spleen that lives in the left upper quadrant. You can see it's cranial caudal extent in 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 psoas muscles as they extend down to the pelvis. Now as we scroll through these sets of images we can start to see portions of the pancreas. This is the pancreatic tail. If we focus on that we're going to see the body come into the picture. Pancreatic neck over here and that dive a little bit downwards so far in the pancreatic head, and the uncinate 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 vena cava. We can also see adjacent to the inferior vena cava is of course the abdominal aorta. Up here is the stomach, you can see the gastroesophageal junction in this location. This is the fundus of the stomach. As we scroll more anteriorly you're going to get to the gastric body over here, the gastric antrum over here, gastric pylorus. That meets up with the duodenum which runs downwards and goes across the midline over here to form the jejunum 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's going to be the hepatic flexure. At that point this becomes the transverse colon. You can see the transverse colon very nicely going all the way across the midline. Up again, in the left upper quadrant where now is the splenic flexure, specifically that'll be around this location. Then we come downwards again you can see the descending colon. On this image over here you can see the main portal vein splitting up into the right portal vein and the left portal vein. This is the splenic vein that drains into the main portal vain, you can see it coming from the spleen. This is the superior mesenteric vein, this structure over here, which drains the small bowel and the majority of the colon and 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, as you scroll more anterior you can start to see the abdominal aorta. First branch that comes off the abdominal aorta the celiac artery that gives rise to several branches, one of which is the left gastric artery going cephalic, 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 off the aorta is the superior mesenteric artery which is going to be this branch over here that supplies the small bowel and the majority of the large bowel. 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.
