Sonography of the Pancreas and Spleen - SD

Introduction

I'm Dr. Okal Taric, radiologist, from the department of Radiology, Thomas Jefferson University Hospital, and from the Jefferson Ultrasound Research and Education Institute in Philadelphia.

I'll speak to you today about sonography of the pancreas and spleen.

The Pancreas

First, I'd like to talk about the pancreas. I'd like to review the anatomy some details, and highlight the vascular markers for the gland. Then we'll talk about some pathologic manifestations, and the role of ultrasound.

Why Ultrasound of the Pancreas?

Ultrasound is a screening modality for jaundice. Any patient with jaundice should first get an ultrasound. That's a good place to start, and at least to look at the head of the pancreas.

Although CT is much more accurate in pancreatic diagnosis, and also MRI now is a wonderful modality, and they provide more information for us. But we have to remember that not all patients can have a CT. For example, pregnant women, children, patients who have contrast allergies, who may not want to take the risk and undergo steroid prep because a certain percentage of those patients break through with anaphylactic reactions. In these cases, we should be prepared to do a full, proper evaluation of the pancreas. CT is not always available.

Usually in the United States, there are CTs everywhere, even multiple CTs in a hospital. But in some of the countries outside the US, CT is not that available.

Pancreatic Anatomy

Let's look at the pancreatic anatomy. The pancreas is a retroperitoneal structure. It lies posterior to the stomach, so the stomach with air in it would interfere with visualization of the pancreas. But also we can introduce water into the stomach. If we have to do a thorough evaluation of the pancreas, it's a good idea to have the patient drink some water and provide a sonic window for us.

Here we're going to peel away the cutaway the stomach, and right behind it is the pancreas. Notice how the head of the pancreas is hugged by the C loop of the duodenum. This pancreas is very intimately related to a number of very important vessels. Here's celiac axis, splenic artery just above the body of the gland. Behind it is the superior mesenteric artery. Behind it is also the SMV and splenic vein forming the portal confluence. Notice the gastroduodenal artery that lies on the anterior surface of the head. Lots of very important anatomic markers, which we'll talk about in a few seconds.

Here's a very classical, very well-known appearance of the pancreas on ultrasound. This is the splenic vein, and just in front of it is the pancreas. So we have the head of the pancreas. We have the neck, then the body, and here at least a portion of the tail. Then the tail wanders away towards the splenic hilum. So usually it's obscured by bowel gas. And here's a little piece of pancreas that hooks behind the SMV portal confluence, and behind the splenic vein, that's the uncinate process of the pancreas. In Latin, uncus means hook. So this is a portion of the pancreas that hooks behind these vessels.

This is a classical scan through the pancreas. However, this is very misleading because the head of the pancreas is four centimeters long. The body of the pancreas is about two centimeters in length, in the sagittal plane. So we're only imaging a very thin section. When we're hanging around this splenic vein, there are a number of vascular landmarks that we use to identify the pancreas and look for abnormalities.

Vascular Landmarks: Veins

So I'd like to discuss the veins that are related to the pancreas, and that includes the splenic vein, superior mesenteric vein, the main portal vein, and the inferior vena cava.

The splenic vein runs posterior to the body tail of the gland. The superior mesenteric vein travels in a sagittal plane, and the two of them join together in a confluence. So this is a wider area where the main portal vein begins. The main portal vein crosses obliquely in front of the inferior vena cava, which is posterior notice here that the main portal vein is located at the superior surface of the pancreatic head, and the pancreatic head is rather long. Here's the uncinate process, hooking behind the superior mesenteric vein.

Now, there's a number of arteries that are intimately related. There's the aorta, and off of it comes the superior mesenteric artery, which is right behind the splenic vein. Then we have the celiac axis, that's superior to the pancreas. It gives off the hepatic, the left gastric, and the splenic artery. This splenic artery travels along the superior border of the body and tail of the pancreas. Usually, the pancreas goes no higher than the splenic artery. The gastroduodenal artery, which is not drawn here, would lie on the anterior surface of the head of the pancreas.

So let's look at the splenic vein. On ultrasound, splenic vein lies posterior to the body and tail of the pancreas. It ends at the portal confluence, where there's a little bit of a enlargement that resembles the shape of a cobra head. Some people have referred to it as the scallion, the little onion shape. And this is our marker for the body and tail. It's immediately in front.

Here's another classical cut showing that portal splenic confluence a little better here with pancreas anterior to it. Now, the splenic vein is a useful anatomic structure because the pancreas being in front of it, we know that if masses arise are found anterior to the splenic vein, then they are of pancreatic origin. However, if there should be a mass located posterior to the splenic vein, then that's not a mass of pancreatic origin. That would be an adrenal mass or a retroperitoneal mass, or a neurogenic type tumor related, or a sarcoma of some sort, but not pancreas.

The superior mesenteric vein courses parallel and just to the right of its partners superior mesenteric artery. This vessel ends at the portal confluence, where it joins the splenic vein. So it's the SMV portal confluence. This superior mesenteric vein is a marker for three parts of the pancreas. The head is lateral, the neck is anterior, and the uncinate process hooks posterior to the superior mesenteric vein. So we use that as a landmark. And here we have the head of the pancreas, the uncinate behind this portal confluence and neck in front of the portal confluence. If we were a little lower, we would see it in front of the vein itself.

Now, that was transverse. Now, when we look at the longitudinal sagittal scan, the superior mesenteric vein is a vein that looks kind of suspended in the middle of this abdominal cavity. And it ends in a little bulbous appearance, kind of resembling a cobra head. And that's the superior mesenteric vein, but on a longitudinal sagittal section. And this portion here that's bulbous is because of the SMV portal confluence. So the neck of the pancreas is anterior to this, and the uncinate process is posterior to the superior mesenteric vein.

Now, when you look an image like this, very often people see this characteristic kind of appearance of the vein, and they right away think that they're looking at the splenic vein. But be careful because if it's a sagittal section, a longitudinal section, this can't be the splenic vein. This is the superior mesenteric vein ending at the portal confluence. This then is neck of pancreas, and the little echoes behind would be uncinate process.

Very similar appearance on a transverse section of the body where we see the splenic vein. Now, we know we're transverse because we have the spine. There's a cross-section of aorta, cross-section of inferior cava. Here's a little superior mesenteric artery, splenic vein in front. Here we have a longitudinal appearance of a vessel and then spine behind. So here we're transverse. Here's our splenic vein. Here's longitudinal superior mesenteric vein. So we have to be careful to not to mistake the superior mesenteric vein for the splenic vein. The longitudinal superior mesenteric vein is on a sagittal scan. The longitudinal splenic vein is on a transverse scan. And SMA superior mesenteric artery, aorta and spine are posterior to the splenic vein.

Now, the main portal vein, the main portal vein crosses obliquely and anteriorly to the inferior vena cava. The pancreatic head extends just inferior to that point of crossover. So here we are on a sagittal section. This is the inferior cava. This round dark area is the main portal vein crossing in front of the IVC. That's our marker for the head of the pancreas. So all of this is head of pancreas that extends about four centimeters inferiorly, four centimeters in length. So this is our marker for the cranial aspect of the pancreatic head.

Vascular Landmarks: Arteries

Now, the superior mesenteric artery on a transverse scan, the superior mesenteric artery is cut cross-wise, cross in cross-section as a circle located anterior to the aorta. The superior mesenteric vein has a very characteristic echogenic triangle of mesenteric fat around it that makes it easy for us to recognize. And in front of that then is splenic vein and then pancreas.

Now, you may have a patient with a lot of bowel gas, but if you just visually spot that echogenic triangle with the hole in the middle, you know you are at the superior mesenteric artery. So that's gonna be aorta in the back. The left renal vein crosses in between. The splenic vein is just anterior, and anterior to that is body of the pancreas. So we know that at least this part is part of the pancreatic body.

Again, an echogenic triangle of fat on a transverse scan with a hole in the middle is SMA. In front of that is splenic vein. In front of that is pancreas. Notice here that the pancreas has a little hole in the back. That's the common bile duct passing through the head of the pancreas, posteriorly, and a little hole anteriorly. And that's the gastroduodenal artery that lies on the anterior surface of the head.

Now, if you ever see a picture like this, which is very confusing, and you use these landmarks to help you sort out where you are, you know, your transverse 'cause. Here's the spine. This looks like aorta and vena cava. And then you have all these masses, but you recognize an echogenic triangle of fat with a hole in the middle. So, you know, that's SMA, it's far and spaced far away from the aorta. And then you realize that you are staring at masses all over this region. The region of the pancreatic gland.

On a sagittal scan, the superior mesenteric artery originates anteriorly off the aorta. The first branch off the aorta is the celiac trunk, and very close after it comes to superior mesenteric artery. Now, the celiac trunk is short. It points, I think of it as a long finger that points to the body of the pancreas, but the superior mesenteric artery curves and has a long course and parallels the abdominal aorta. It also has quite a narrow angle in between, through which pass some important anatomic structures, which we will address later. That superior mesenteric artery has an echogenic kind of border around it, because that's that mesenteric fat that surrounds it. In front of that is splenic vein. And in front of that then is body of the pancreatic gland.

Now, this shallow acute angle of the superior mesenteric and aorta, there is a left renal vein that has to pass over the aorta comes right through this acute angle. So sometimes when the two arteries have too high of a pressure, they can pinch off the left renal vein a little bit, inferior would be uncinate process. And then the third part of the duodenum crosses over. But the important thing is the left renal vein. So if you're looking at this sagittal section of the body and you see the aorta, but you do not see a normal superior mesenteric artery paralleling the aorta, you see that you recognize the vessel, but the angle now is very wide. And then you notice that all this tissue is surrounding it, displacing the artery from the aorta. And this is all an invasive tumor of the pancreas, recognized by with invasion of the superior mesenteric artery due to that narrowing.

Now, the celiac artery, I already mentioned that it's the first major trunk coming off the aorta. It's not very long. It looks like a long finger pointing to the body of the pancreas. Notice that we have the abdominal aorta and it's paralleled in front by a thin hypoechoic stripe. That's the crus of the diaphragm or a slip of the diaphragmatic muscle, which stops approximately at the takeoff of the celiac artery. And then comes the superior mesenteric artery. This patient shows the collapsed left renal vein passing between superior mesenteric artery and aorta. This celiac axis artery points to the body of the gland behind, which is the splenic vein.

The splenic artery has a tortuous course, and it travels along the superior border of the pancreas. It's a marker for the cranial edge of the pancreas. It lies superior to the vein, which is directly behind the body of the gland. So it's a marker for the cranial aspect. Notice also that it has a very tortuous course, and it sort of weaves in and out, and up and around the top part of the gland. We don't know why it tends to be tortuous, but even in young people, it may be somewhat tortuous.

Now, this is something to remember because there's a pitfall that can occur with this splenic artery. If you ever see a little cystic mass in the pancreas, the first thing you should think of, could this possibly be a piece of the artery that's weaving in and out, and you turn on the doppler, and sure enough, this was just the splenic artery. Any cystic structure then in or around the pancreas should be interrogated with color doppler at least.

Now, the same thing holds for a little calcification if you see a little calcification coming from the gland. And here's another example, little calcified rounded mass with shadowing. Here's another one. Looks like a calcified structure in the body of the gland with shadowing. Turn on the color, because this could be that tortuous, calcified splenic artery, and it often calcified. So do not think that this is a calcified little mass in the pancreas. It's in the artery.

Summary of Vascular Markers

So here's a summary of all these vascular markers for the pancreas. The splenic vein marks the posterior aspect of the body and tail of the gland. The superior mesenteric vein and the confluence are borders of the head, neck, and uncinate process. The splenic artery marks the cranial edge of the body and tail. And the main portal vein not seen on this picture here marks the cranial margin of the pancreatic head.

So as you're scanning around and you see some unusual tissue, you wonder where you are, what's going on. You immediately refer to your landmarks. You say, okay, spine, aorta, IVC, you can recognize the SMA surrounded by an echogenic triangle of mesenteric fat. And now you know exactly where you are. And in front of that should be the splenic vein, which we can't find. Instead, there's some lumpy lobulated solid tissue with small cystic spaces. And this turned out to be a diffuse pancreatic cancer involving the gland and already invading the splenic vein.

Now, if you are asked to do an ultrasound of the pancreas itself, you should not only scan all of these margins, but all of these surrounding vessels. But you should also do sagittal sections of the pancreas. So I'd like to go over these.

Let's look at a sagittal section through the head, through the neck, through the body, through the distal tail, I'm sorry, distal body or proximal tail, and through more of the distal body. Let's see what those sections look like.

Here goes sagittal section through the head. Our markers are IVC with the crossing main portal vein just below is the four centimeter long pancreatic head. We move to the left towards the left of the patient, and here we run into this vessel that has a blunted end, looks like a cobra head, but it's on a sagittal. So we know that superior mesenteric vein and in front would be pancreatic neck and behind our uncinate process echoes, we move more to the left of the patient, and we pick up the aorta. With SMA in front is splenic vein. The celiac points to the body of the pancreas. We go more to the left, and we see two rounded structures, like two eyes looking at us. That's the splenic vein behind the body of the pancreas, which lies behind the antrum of the stomach. And the one that's more superior is the splenic artery, which rides along the superior part of the body and tail of the pancreas. And then as we progress a little more lateral, we can follow the echogenicity of the tail, and then we will lose it. As it heads towards the hilum of the spleen, there will be too much surrounding bowel gas.

Examining the Pancreatic Gland

So I want to bring you back, now that you know how to examine an entire pancreatic gland, I wanna bring you back to this classical picture that on a daily basis is imaged by sonographers. Is this a normal pancreas? Well, we see aorta, SMA, IVC, part of the splenic vein. We see some echoes from the pancreas uncinate head, neck, body looks okay, a little heterogeneous maybe. But we don't see any unusual problem. That's about as much as you usually get on a standard view of the upper abdomen. You don't get the additional cuts, so you cannot say that the pancreas is normal. All you can really say is that portions visualized are normal, or portions visualized are grossly normal.

The same patient, a few centimeters inferior, had a mass, a solid mass when biopsied was pancreatic cancer. So this is a sagittal of that cancer. This is IVC. This is a main portal vein. Here's the pancreatic head and hanging off the inferior part of the head is this solid pancreatic cancer. So we have to be careful. We do not want to mislead clinicians by saying there's a normal pancreas when we haven't examined the complete gland.

Pancreatic Duct

Another little anatomic detail is the pancreatic duct. Now, this is a small little tubular structure that runs down the very center of the gland, seen here as a thin tubular structure down the middle, surrounded by pancreatic echoes on both sides. There is no vessel that runs down the middle of the pancreas like this. So the only thing there would be the pancreatic duct, which is not more than two millimeters in diameter.

Here's another picture of this visible little duct here surrounded by pancreatic echoes. And if you follow it, it will curve around and join the common bile duct, and then onto the duodenum through the ampulla of Vater.

Now, sometimes you look at the image of the pancreatic area and you see a dark stripe. Be careful, don't call this a pancreatic duct until you're sure that it's actual. And what I mean by that is, follow the course of this stripe. This does not assume the course of the pancreas, even though it kind of faked out at first, you'll notice there are no pancreatic echoes on the other side. So this is not the pancreatic duct. In fact, this is the posterior wall of the antrum of the stomach. Here's the anterior wall, and this is internal collapsed mucosa, and then filling with the gas. So just to call pancreatic duct dilatation, we wanna see it directly inside the gland. And if you follow that posterior wall, you'll see that it blends and stays with the stomach.

The common bile duct courses through the head of the pancreas. It should not be mistaken for pseudocyst, especially when it's enlarged, but when it's enlarged, what we should do is track down the duct. Take small sections inferiorly to make sure there's no stone or tumor down there. Here's the head of the pancreas, SMV, SMA, and lateral is the head. There's the distal duct with an obstructing calculus directly embedded in the distal duct. So we wanna follow that, make sure we don't miss that.

Echogenicity Variations in the Pancreas

One other thing you should know about the pancreas is that it can have two shades of echogenicity in the head. Sometimes you'll see that the most posterior part is a bit hypoechoic. Embryologically, the pancreas originated from fusion of the dorsal and ventral anlage, so called anlage. Now, the reason it has different shades is some investigators tell us that there are different fat content within this mass, therefore different echogenicity. The important thing here is not to mistake this for a mass notice. It has a fairly straight edge of demarcation.

Here's another one, hypoechoic more in the uncinate compared to the anterior part of the head. Sometimes it gets kind of prominent. We watch for the internal architecture, but if it gets too round and too dark, we have to think of a mass. Now, this one was a cancer in the head of the pancreas, and these were just areas of different fat infiltration.

Pancreatic Pathology

Let's look at some pancreatic pathology. We'll look at acute pancreatitis, chronic pancreatitis, some of the pancreatic tumors like cancers and some others.

Acute Pancreatitis

Now, acute pancreatitis is usually a diffuse process, although it can be focal. It's a diffuse enlargement of the gland, and the gland becomes hypoechoic relative to the liver. In this case, it's not hard to recognize because the gland is swollen. But we have to be careful when, let's say it's a subacute situation, because sometimes the liver is fatty, which makes it more hypoechoic, which could make the pancreas look hypoechoic. So we have to watch this relationship and see which of the organs is abnormal. Is it the liver that's hyper too hypoechoic, which makes this look hypo? Or is this truly acute pancreatitis, hypoechoic? And this is just a normal liver.

On this sagittal image, the head is markedly enlarged. Here's the portal vein located inferiorly. Here's the bile duct heading into the posterior part of the head of the pancreas. Looks large and bulbous. And this was also involved with acute pancreatitis.

Acute pancreatitis can be focal and that can mimic carcinoma. That's why we do follow these patients in the next three or four weeks with a scan to make sure that all of this has resolved. This type of focal appearance is more likely to occur in the pancreatic head than it is in the tail. If it occurs in the tail, it's much more likely that that's going to be a carcinoma.

There are complications of acute pancreatitis. If this is not treated, and it does not start to resolve, the process can worsen. It can turn into a phlegmon. A necrosis of the gland can ensue. It can turn into an abscess, it could bleed into itself. If it heals a pseudocyst may form, it can obstruct the biliary tree. There's problems with veins, there's problems with arteries. And we'll see some of these. Here's a pancreas. SMA, splenic vein was in here, and the gland is emus. But off to the side, we saw streakiness throughout the abdominal wall musculature in the retroperitoneum. And this is what a phlegmon looks like, which is formed from edema and continuous leakage of these activated pancreatic enzymes in between these tissues.

Now, pancreatitis can become infected. There will be leakages of fluid around the gland. Sometimes there's areas of irregularity, which could be tissue necrosis. Some if it's super infected, if the patient gets fever, there could be abscess formation. Here's some shadowing when the acute pancreatitis becomes infected. This is a life-threatening complication.

Now, what is the role of ultrasound in patients with acute pancreatitis? Well, it's not so much the imaging of the gland. It's all the other things. First of all, gallstones, patients who have gallstones can have recurrent bouts of acute pancreatitis. Now, usually people think of CT as the imaging modality for pancreatitis, but on CT gallstones are poorly visualized. Only about 15% of gallstones are calcified, which means you can see them on CT. The other 85% of gallstones are not calcified, so they don't show up on CT. So ultrasound would be a great way to first investigate and see what's going on in the gallbladder. We can see biliary ductal dilatation by this swollen emus gland. We can look for the complications that we just talked about. If there's a fluid collection, we can follow the fluid collection with ultrasound rather than keep repeating CTs. We can use it for aspiration of collections and a guidance for drainage. And sometimes we pick up unsuspected cases of pancreatitis.

Pseudocysts

As the process continues and slowly begins to heal. A pseudocyst may form pseudocysts or cystic masses that form 90% of cystic masses of the pancreas. This fluid becomes encapsulated. It's a mass like fluid collection. There's inside is tissue edema, enzymes, blood debris. All of this then incites a inflammatory response. And there's a thick inflammatory fibrous capsule that forms pseudocysts can range from small ones two centimeters in diameter to 20 centimeters in diameter. They can be multiple as they were in this patient who had 1, 2, 3, 4 pseudocysts. They may occur in remote areas. Remember, the tail of the pancreas wedges its way into the splenic hilum. So the pancreatic enzymes can dissect into the hilum, can dissect into the spleen. You can have intrasplenic masses collections. They can extend into the paracolic gutters. They can even extend into the mediastinum.

Now, pseudocysts can have complications of their own. They can become super infected. They can bleed into themselves. They can even rupture. They can have calcifications in the wall. And here we see several of these complications.

Other Complications of Acute Pancreatitis

Another complication of acute pancreatitis is thrombosis of adjacent veins. So intimately related is that splenic vein, that it easily becomes thrombosed superior mesenteric vein can become thrombosed, and the thrombus can extend up into the portal vein as it is in this case.

Another complication happens when the enzymatic juices dissect into an arterial wall and then destroy part of the wall. And pseudoaneurysms are formed. So that can happen in when any one of those intimately related arteries like splenic artery, gastroduodenal artery superior mesenteric artery, hepatic artery. So once again, any cystic structure in or around the pancreas should be interrogated with doppler. Here was an innocent looking little cyst, but when they turn on the color doppler, it had a to and fro yin yang type of flow, which is seen with a pseudoaneurysm.

A pseudoaneurysm can occur in the splenic artery. In the hilum, these enzymes dissect into the hilum, and erode the spleen. And a similar appearance can also be caused by a pseudocyst. So pancreas can cause a large cystic mass in a spleen in two different ways. One is that it's a pseudocyst in the spleen. And the second way is that it's a large pseudoaneurysm of the splenic artery for which color doppler will be very useful. Always turn on Doppler with pancreatic cystic masses or splenic masses.

Chronic Pancreatitis

Now, there's a chronic pancreatitis that can occur. Now, once the gland has undergone these insults, it can heal with fibrosis, calcifications can be precipitated. Usually what we see is a smallish gland with increased echogenicity, and it's very heterogeneous with punctate cal, sometimes coarse causing shadowing. There's an irregular dilated beaded pancreatic duct. The pancreas echoes are on both sides of this arrangement. And fluid collections can also form.

Now, this chronic pancreatitis sometimes is focal, and most of the time it's diffuse, diffuse process. But sometimes it can be focal and can mimic a carcinoma. The giveaway is the areas of bright reflectors and shadowing, which is the calcium. So we can have scattered calcifications, that would be our clue. And sometimes we see small cysts in the pancreatic mass, the focal pancreatitis. This was chronic pancreatitis. These patients have to be followed. Sometimes the biopsy was done, but the calcium would be a very telltale sign, important telltale sign of chronic pancreatitis.

Pancreatic Cancer

Cancer of the pancreas. Now, cancer is hypoechoic. Cancer of the pancreas is dark, it's hypoechoic. There have been no cancers of the pancreas that have been hyperechoic. So these are, here's a hypoechoic mass in the head of the pancreas. Here's a hypoechoic mass in the body of the gland. 60% of the pancreatic cancers are in the head. 40% are in the body and tail region.

Here's a patient with pancreas. And as we were imaging down the tail, we noticed a hypoechoic mass lobulated, irregular mass, extensive down the tail. Now, when we see such a mass, we immediately look for adjacent vessels, because invasion of the vessels, or encasement of the vessels is a common presentation. Here, the splenic vein is barely visible because it's invaded. And here on a sagittal section, the arteries present, but the vein is hardly discernible.

We will check for biliary obstruction. Here's bile duct dilatation. At the end of the duct, we see a hypoechoic solid mass. And we look for biliary dilatation inside the liver, for which we can do color doppler to show that those are not vessels, that they're bile ducts that are not filling with color.

A mass in the head of the pancreas will cause obstruction of the pancreatic duct. That may means the duct is enlarged, and the duct shows up as a beaded type of tubular structure running down the middle of the gland. So here we have SMA splenic vein, pancreatic duct down the middle of the gland, and a very abnormal mass in the head of the pancreas. And here's the cancer also on this slide.

Now, after we've assessed the pancreas, it's very common for the pancreas to metastasize to the liver. So we're right there. We check the liver. Here's a metastasis, a focal lesion. Here's another patient. This changes everything. This is now stage four disease. You can easily take a needle, stick it in there, get tissue diagnosis, and have a diagnosis. In 24 hours, you can see adjacent lymph nodes. You can see the tumor invading locally. Lots of things to pick up with ultrasound.

Cystic Neoplasms and Other Tumors

There are cystic neoplasms that occur in the pancreas, such as microcystic adenomas. Cystadenoma is well known. Macrocystic adenomas, including mucinous cystadenocarcinoma, cystadenoma can occur. There are tumors called IPMNs, intraductal papillary mucinous neoplasms of the pancreas. There are larger multi septated cystic masses that grow quite large in the tail.

There are also a whole separate category of pancreatic masses that originate from the endocrine part of the gland. All the cancers that I've been talking about till now are originating from the exocrine part of the gland. The endocrine part of the gland have unusual presentations. These are these islet cell tumors, and they have different names based on what they secrete. So if a patient is having too much insulin and having episodes of hypoglycemia, then these are insulinoma. If they have high gastric secretion production, these could be gastrinoma. There are lipomas, there's glucagon, there's somatostatinomas. These are these tiny ones. They're often not even visualized. We're lucky here in this case to see a small little nodule. Usually they're small, very hard to find. But the endoscopic ultrasound that the gastroenterologist passes into the stomach and images from inside the stomach, that's really the most sensitive way to find these small tumors, which could be biopsied.

It's not unusual for surgeons to call us into the operating room for us to come with our laparoscopic ultrasound to help them find the little mass, which they can't see. So what happens is the surgeon has the abdomen and retroperitoneum in the gland exposed. We come to the operating room, glove up, dress up in sterile technique, cover the probe, and then run our probe over the surface of the gland after they put a little saline in, of course. And then we can sometimes pick up a very small tumor with our high resolution laparoscopic probe. In some cases we can't even find it. Sometimes the surgeon just does a blind kind of a resection.

Lymphoma of the Pancreas

This is a very unusual disease of the pancreas, and that is lymphoma of the pancreas. Here's two cases for you to look at. They're just infiltrative, very large, not very characteristic masses. They're rare to be primary in the pancreas. Most of the time. There's other disease elsewhere. There will be enlarged lymph nodes, et cetera. So that's usually a very difficult diagnosis to make.

The Spleen

Okay, now the spleen. The spleen is a small organ that sits in the left upper quadrant, very closely applied to the left hemidiaphragm. It almost looks like the echogenicity of the liver, except that it does not have the bright portal vein walls that are characteristic of a liver. The spleen has a different architecture. It's made of red pulp, white pulp. So it has basically a nice homogeneous texture with a few little vessels penetrating it that you can see near the hilum area. It's homogeneous, moderately echogenic. The spleen sometimes moves around. There is a phenomenon called the wandering spleen, also called floating spleen, ectopic spleen, accessory spleen, aberrant spleen. The spleen is on a vascular stalk, and sometimes it can move around the abdomen from the left upper quadrant to the middle. This one landed in the pelvis. It looked like perhaps even an endometrioma in the pelvis. Here's the ovary. Here's the retroverted uterus. And this patient eventually twisted its vascular pedicle, and the spleen underwent torsion, and the diagnosis then was proven.

Splenomegaly

What about splenomegaly? When is the spleen too large? Now there's conflicting information in the literature. Some say over 14 centimeters long. Others say that you should just look at the way the spleen looks in relation to the kidney. Certainly if the spleen is much longer and larger than the adjacent left kidney, that's splenomegaly. I personally like to use 13 centimeters, at anything beyond that would be splenomegaly. Others might use 14 or more. If I sometimes think the spleen is too long, but I'm not sure if it's really enlarged. I sometimes use more than six centimeter thickness as another indicator that that spleen is enlarged. Certainly if it has a mass effect on the kidney, that's another sign of enlargement.

Accessory Spleens

Around the spleen, you'll see small isoechoic nodules. These are quite common. They're usually small, less than three centimeters in diameter. They are accessory little spleens. They're developmental. They have their blood supply coming from the splenic artery. You can see them in up to 10% of patients. They're more common when the spleen is enlarged. They're usually solitary, but they may be multiple. But importantly, they should not be confused with lymphadenopathy and should not be confused with masses from adjacent organs like an exophytic renal mass. So you have to be aware of this.

Splenosis

Now, there's another way that we can see little spleens in the body. Now, what I showed you just before was accessory spleens. There is such a thing as splenosis, these small little masses that are splenic tissue. But splenosis occurs only after splenic trauma or rupture. And then we have these little islands of splenic tissue that spontaneously transplant around the peritoneal cavity. They parasitize blood supply from the peritoneum they can implant anywhere. They have a very characteristic appearance. They can even extend down into the pelvis. They can attach to peritoneum, omentum, mesenteric surfaces. In the pelvis, they simulate endometriosis, which happened in this patient. However, she had had a splenectomy after motor vehicle accident, after her spleen was ruptured, and she had several of these little masses. These were removed. They were splenic tissue splenosis. They parasitize blood supply from adjacent areas. They're not fed by the splenic artery.

Cystic Masses in the Spleen

There are masses that occur in the spleen. Here's a list of cystic masses that can occur. We'll show you a few of these. Here's a pure cyst that occurs in the spleen, that true cysts with a true lining are rare. Most of these are secondary to old trauma or hematoma, or even a pseudocyst inside the spleen. They can be complicated by hemorrhage or infection, just like any cyst.

Most of the time when there is a splenic laceration or hematoma that is handled by CT. But in some patients, like in children or young adults that are stable, that do not need to have CT follow up, for example, we can evaluate and follow the spleen. Look, here's, we have linear hypoechoic defects throughout the spleen, which are a laceration that was stable. Here's a patient who developed a spontaneous bleed on anticoagulants. Both were stable, did not require any surgery.

We can see subcapsular hematomas. That's, and there is sometimes difficulty in defining the extent of the subcapsular hematoma because it can often look very much like the spleen itself. One thing that could be helpful is to do doppler and watch where the vessels end. So we would know that's the end of the spleen. And all this heterogeneous material outside is perisplenic hematoma.

Another thing that you should be aware of is that the left lobe of the liver can come around and hug the spleen. Now it gives kind of a two-tone, double shaded appearance to the spleen. The splenic tissue itself is homogeneous, and look for little portal vein walls inside this piece of liver that's coming way over to the left from the left lobe. This is easily mistaken for subcapsular hematoma. So if you see such a thing, such an appearance, think of liver adjacent to spleen rather than a hematoma.

There can be a liver abscess. It looks like an abscess anywhere in the body. Usually regular thick walled with internal debris, especially think of bacterial endocarditis, secondary to embolism or septicemia in such patients like drug abusers or immunocompromised patients.

Hydatid disease is an endemic disease in certain areas of the country, usually related to sheep raising areas. It sometimes bypasses the diagnostic list, but in endemic areas, this certainly is known. Here's two examples of multi septated masses. Little small micro abscesses can occur in the spleen, just like in the liver. And these are usually due to fungal infection. And have little small target lesions with a little echogenic nidus, which is the bullseye lesion of the micro abscess.

Intrasplenic pseudocysts can occur after trauma, which means that there was an organized hematoma after an occult rupture, or it can originate from the pancreas. A pseudocyst from dissection by the enzymes. Cystic masses around the spleen can be due to arterial problems. In this case, a splenic artery aneurysm, which can form after atherosclerotic disease or from septic emboli infection or trauma. This has high morbidity and mortality, and usually has to be treated when it's over one and a half to two centimeters in diameter. It's somewhat rare. The pseudoaneurysm would be more common from pancreatitis or trauma. And in this case, there are two of these. These happen to be intrasplenic pseudoaneurysms.

More cystic lesions that occur in the spleen could be primary. A metastasis from a primary tumor that is cystic, like an ovarian cystic mass. Sometimes there's a metastasis that undergoes cystic degeneration, maybe internal hemorrhage, necrosis or infection. And that can cause this irregular thickened appearing mass, which would be suspected of being tumor or an abscess.

Solid Masses in the Spleen

When we talk about solid splenic masses, again, we have a list of things. The most common thing would be little granulomas. These are little calcified granulomas, echogenic spots and dots throughout the spleen. Tiny little shadows can be demonstrated coming from these, and these usually are due to granulomatous disease, exposure to histoplasmosis in some areas, tuberculosis. And think of sarcoidosis.

Now, spots and dots in the spleen can also be caused by something called Gamna-Gandy bodies, this is known in MRI, but occasionally can be picked up on ultrasound. These are siderotic nodules, nodules of fibrous tissue that contain iron and calcium salts. That's why they're picked up on MRI. And these are actually little healed, focal hemorrhages with necrosis. That's why they become hyperechoic. When you see these, you have to think of portal hypertension. Sickle cell anemia is probably the next most common cause. And then there's some other more unusual entities. However, seeing these spots and dots, you think of granulomas, you think of Gamna-Gandy bodies. You think of histoplasmosis sickle cell and disseminated pneumocystis can look just like that.

Here's a patient with HIV. He has disseminated pneumocystis carinii. And here's his spleen in the left upper quadrant with pancreas, with, I'm sorry, left kidney. Little spots all over the parenchyma. Here's the liver also with echogenic, numerous foci and the right kidney. These patients we used to see more of these in the past when patients were treated for HIV with pentamidine. So they would inhale the pentamidine to protect their lungs, but the disease would go then systemic and affect their parenchymal organs like liver, spleen, pancreas, and kidneys. We don't see as much of this because HIV is much better controlled. But in case you do spot this, you should think of HIV first.

Infarcts are a classical wedge shaped, peripherally located hypoechoic defect, which can be seen with septic emboli or just simply thrombosis of vessels. It's the most common focal lesion in the spleen with septic emboli. We have to think of drug abusers. It occurs in patients with endocarditis, atrial fibrillation, and patients who actually get vessels thrombosis in the spleen. We have to think of sickle cell disease, pancreatitis, leukemia and lymphoma.

Hemangioma in the spleen looks just like hemangioma in the liver. They're rare in the spleen, but occasionally you'll see them. They're typical masses. They do have variable features. They're indistinguishable from any other etiology. So this can be a difficult diagnosis. MRI is usually helpful, and they may actually even require splenectomy to make the final diagnosis. The spleen size, however, is usually normal.

Hemangioendotheliomas can occur in spleen. These are benign neoplasms. They're asymptomatic, often incidentally discovered at autopsy.

Now, lymphoma, that's a common mass of the spleen. So if we see single or multiple hypoechoic solid masses throughout the spleen, we have to think of lymphoma. It could also be hyperechoic masses. We would look for additional lymphadenopathy and additional history.

Now metastases, that's another big category. So we've got like granulomas. Hemangiomas, lymphoma and metastases in the spleen. Rarely these are seen, or at least they used to be rarely seen outside of autopsy. But now with all this imaging techniques, we do see masses, late manifestation of metastasis in the spleen. Usually they arrive thereby hematogenous spread. The important tumors are melanomas, breast, lung, and colon that like to do this. And the longer patients survive with better treatments, the more likely we are to see these manifestations of advanced disease.

And finally, at the very end, there's one tumor that's kind of specific or special to the spleen, and that's the angiosarcoma. It's very rare. It's a primary malignant tumor originates from endothelial cells. It's usually solitary. It's very heterogeneous and complex looking. And it's usually the last thing on your differential that the patient can present with. And one thing you should remember is that they can spontaneously rupture and could actually present with a hemoperitoneum and an acute abdomen coming from this complex mass in the spleen.

Conclusion

So, that's an overview for you of the pancreas and spleen by ultrasound. Thank you for your attention.