Sonography of the Liver - SD

Introduction

I'm Dr. Oksana Altaic from the Jefferson Ultrasound Research and Education Institute at Thomas Jefferson University in Philadelphia.

I'll be speaking about liver sonography. We're going to discuss the normal liver. We'll talk about doppler of the hepatic vessels. We'll talk a little bit about diffuse liver disease patterns, then move into portal hypertension and focal liver masses.

Normal Liver Appearance

The normal liver, when we look at it sonographically, we pay attention to the size of the liver, the shape of the liver, the echogenicity, and the echo texture.

The echogenicity and echo texture are two different things that we talk about. Echogenicity has to do with the level of brightness of the liver parenchyma, and we use portal vein walls to compare that. And texture has more to do with the homogeneity of the liver.

The liver is very susceptible to technique. We have to make sure that we have a nice, smooth TGC curve. We want to make sure that the penetration goes all the way back to the diaphragm.

Here is this curvilinear bright structure. We would like to have the vessel wall, a vessel lumen clear of extraneous echoes. And when we scan the liver, we want to make sure that we clear all of the margins of the liver.

In this case here, we have very good technique coming through this side of the image. We have echogenicity clear vessels, we get through to the diaphragm, but here we seem to have some kind of division, some kind of drop out of sound. So we would have to correct that, either apply better pressure on the abdominal wall, and try to even out the echogenicity here of the liver.

One thing that's very important, and this is important for all structures that we image in ultrasound, we always want to be able to see at least two to three centimeters beyond the margin of any organ so that we can exclude possibility of any exophytic masses or any kind of adjacent masses that can affect the organ.

In this case here, this is the liver. The inferior edge of the liver would be here, but because we were trying to clear two to three centimeters beyond the margin, we noticed that there was a mass hanging off the inferior edge of the liver. We would've never seen it if we would've stopped our picture at the inferior margin of the liver.

By the way, this was a hepatocellular carcinoma, a hepatoma five centimeter hepatoma hanging off the margin of the liver. And if you think that this is an anecdotal or unusual case, here's another case that we had fairly recently hanging from the inferior margin of the liver was this large mass, another hepatocellular carcinoma, hepatoma, and that's the right kidney here.

Echogenicity Comparisons

As you scan the abdomen, you should always have in mind the different parenchymal organ echogenicity and have a kind of a relative scale in your mind of the different echogenicity.

The renal medulla is the least echogenic of all the parts of upper abdominal organs. It is much less echogenic than the cortex of the kidney, which in turn is less than or can be equal to echogenicity of the liver. We used to think that equal to the liver was abnormal, but now we know that especially in young people, cortical echogenicity could be equal to liver echogenicity.

We also know that the liver is less echogenic than the spleen, but that's something difficult to ascertain because usually the liver and the spleen are not on the same picture, and you would really need them to be side by side to tell which one is more or less echogenic that can happen sometimes.

Now this is a scan of the left upper quadrant. We're looking at the spleen here, and we notice that the spleen has a sort of a double shade, has a darker area and a more brighter area, almost like a double shaded spleen. However, we also note that there are some little vessels in this part of the spleen, not so much seen here. And then we realize that this is liver, this is the left lobe of the liver going all the way across to the left, hugging the spleen, and so that it looks like it's a part of the spleen and it isn't. So this is liver, which is indeed less echogenic than spleen. And this is not to be mistaken for a subcapsular hematoma. Sometimes this is mistaken in the spleen. So there's our proof.

The liver is also less echogenic, or equal in echogenicity, to the pancreas. Pancreas usually more echogenic, but they can be equal, especially in younger people. So here is pancreas, and here's the left lobe of the liver, and they're fairly equal. When we compare echogenicity, we should be comparing at a similar depth of the beam.

One more thing here, that the pancreas itself is less echogenic than retroperitoneal fat, which is hyperechoic, and also less echogenic than the renal sinus echoes. So renal sinus echoes and the retroperitoneal fat are hyperechoic and the most echogenic of all of these parenchymal organs.

Intrahepatic Vessels

When we look at the liver parenchyma itself, we realize that there are little holes throughout the liver. Sometimes we see little cylindrical shapes, and some of them have bright walls, and some of them do not. So then we have to figure out what we're looking at when we do ultrasound sonographic.

The vessels that are visible within the parenchyma of the liver are the portal vein walls and the hepatic veins. The hepatic arteries and the bile ducts typically are not visible within the parenchyma of the liver unless they are abnormally dilated. We can see them in the porta hepatis, which is just outside the liver. But as far as being inside the liver, we only see these two vessels.

If you think about the liver, you realize that there are four tubular systems that go throughout the liver. We have the portal venous system, the hepatic arterial system, and the bile ducts. These are intimately related at the porta hepatis. They join together as partners in the portal sinus, portal triads, and they stay together throughout their entire branching throughout the liver. The fourth tubular system is the hepatic veins.

The hepatic veins drain the liver superiorly towards the IVC inferior vena cava. They stand alone. They do not have anything associated with them, and that becomes important to us. We'll see in a minute. So the portal triads then are maintained throughout the liver. That's partially what is causing this reflectivity of the walls. Portal veins have bright echogenic walls, and we use this for comparison of parenchymal echogenicity.

What happens is the main portal vein, it enters the liver through the porta hepatis and almost immediately splits into a right and left portal vein. The largest portal veins divide horizontally approximately in the middle of the liver, and they supply lobes and segments, and they carry blood flow into the liver.

The reason that portal veins have bright walls is number one, because of the portal triads, which is the portal vein, the little hepatic artery in the bile duct. So all we're seeing here is the portal vein. The little artery and duct are small, so they just provide reflectivity. We also have some reflectivity from Glisson's capsule from the little lymphatics and nerves and connective tissue around the portal triad. So that's why portal veins have bright walls, hepatic veins do not.

Why is that? Well, it's a matter of contrast. The hepatic veins have imperceptible margins. They actually have walls, but we just don't see them. If we look at what they look like by configuration, they're more vertically oriented. They enlarge towards the inferior vena cava, and they actually have sort of an umbrella configuration where the spokes of the umbrella come together superiorly, and the rest of the spokes drop down throughout the liver.

These veins are found between lobes and segments. So we use them as anatomic dividers, and they carry blood flow out of the liver. They do not have any other adjacent little structures, therefore, we do not perceive their walls.

Here's an umbrella just for your imagination. You can see that the spokes of the umbrella come together at the top, which is here. So if we take a slice through the very superior portions of the liver, we can see longitudinal orientation of the hepatic veins. Now, as the veins drop down and we take a transverse section lower, these veins will be cut and look like circles. So here is the middle hepatic vein, and here is the right hepatic vein showing us lower in the liver as a cross-sectional configuration cross-section, which we would be doing through the spokes of the umbrella.

Having said that, we always find exceptions to the rule. I just told you that portal veins have bright walls, and now all of a sudden I'm showing you a picture of a portal vein that does not have bright walls. Some portal veins may not show echogenic walls because they become parallel with the beam. Parallel is the worst angle for B scan. So we're losing resolution and we simply lose resolution of this portal vein wall.

Here, on the other hand, are hepatic veins. I just told you that hepatic veins do not have bright walls, and all of a sudden I'm showing you a big hepatic vein with bright walls. Well, it is true that some hepatic veins may show echogenic walls. That's because they're large veins and they have thick walls, so they do have reflectivity, but also in this case, this vein is completely perpendicular to the sound beam, and that's the best angle for B scanning. Therefore, we see the hepatic vein wall. So two exceptions to the rule explained by angles.

Anatomic Landmarks on Scans

We have some now a little bit of insight into the anatomic landmarks on transverse scans of the liver. And let's look at these in high portions in the upper parts of the liver, we see large hepatic veins coming together into the inferior vena cava.

In the mid portions of the liver, we see the portal veins kind of horizontally situated, the left being a little higher than the right, but nonetheless, with the bright walls that we know now that we're in the middle of the liver.

If we look at transverse lower sections of the liver, we don't see any big veins. We see an echogenic line here. This would be where the falciform ligament comes in, and the umbilical fissure, the fissure for ligamentum teres. And that will mark the lower parts of the liver for us. So we'll know for high, mid, or low in the liver.

Ligamentum Teres

Since I mentioned ligamentum teres, let's talk about that ligamentum. Teres means round ligament. We have different round ligaments in our body, but this is the round ligament in the liver, which is the obliterated fetal remnant of the umbilical vein. So the fetal umbilical vein, once the fetus is born, there's no need for that vein. So the vein clamps down and becomes almost like a thick fibrous kind of cord located within a fissure within the fissure for ligamentum teres. The fissure has a little fat in it. That's what gives us bright reflectivity. So somewhere in here is the collapsed obliterated ligamentum teres surrounded by echogenic fat.

This is a transverse section of the left lobe, and that becomes a divider of the left lobe into medial and lateral segments on a transverse scan. Also, notice that there's some shadowing behind this. And the reason that it shadows is because, not because it's calcified, and this should not be mistaken for a calcified mass, but it's because the ultrasound beam strikes this at 90 degrees, which is directly striking this fibrous cord. That shadows behind it. As soon as you change the angle a little bit, that shadow angle will disappear. If it was truly calcified, there would be shadowing no matter what angle you come from.

The fetal umbilical vein came into the umbilical segment of the left portal vein. We can see this when we cut the liver sagittal at this precise level. We are now taking a sagittal image, and we can see the brightness of the fat surrounding the ligamentum teres within this umbilical fissure. And notice that it goes directly into the umbilical segment of the left portal vein. So that's where the fetal umbilical vein enters the portal system. This vein may recanalize in portal hypertension, and once again, it is a divider of the left lobe.

Ligamentum Venosum

While I mention fetal remnants, I'll mention the ligamentum venosum. Ligamentum venosum is the obliterated fetal remnant of the ductus venosus. The ductus venosus carried blood out of the liver in the fetal circulation, blood entered the liver, but there was no reason to stay in the liver. So there's a ductus venosus that right away carries the blood out towards the inferior vena cava and towards the fetal heart. That ductus collapses once the fetus is born, and it lies within the fissure for ligamentum venosum.

Here on a sagittal section, that fissure appears to be a bright line, which is located between the caudate lobe and the left lobe of the liver. Behind the caudate lobe is the inferior vena cava. Okay, when we turn 90 degrees and do a transverse section, the fissure appears here again as a bright echogenic line. Somewhere in here, we don't know where is the collapsed ductus venosus probably closer here to the umbilical segment of the portal vein, so it would've come out. And on higher sections, it will enter the inferior vena cava. Notice that that fissure is a broad plane. It's a line on transverse, it's line on sagittal, so it is not a linear kind of fissure, but it's rather fairly broad. And that is our divider for caudate lobe from left lobe of the liver.

This vein does not recanalize in adults. You don't see this vein ever again, except perhaps in the very small neonate that has umbilical vein catheters, you might see it, but once the child grows, this vein is obliterated and does not recanalize in portal hypertension.

Caudate Lobe

I mentioned the caudate lobe. When you think of caudate, you think of something caudal, but yet that's not really what this means. Caudate in Latin means tail. So the caudate lobe is like the stubby tail of a dog. Here's a little puppy here, and it's actually one of the more cranial parts of the liver.

We pay attention to the caudate lobe because the caudate lobe is functionally an autonomous segment. It is often been said that it is spared in liver disease. It has its own blood supply. It takes blood supply from the right and the left portal veins, and you can prove this to yourself if you carefully scan. If you have a good patient, a thin patient, and you look around the portal veins, you can see small branches entering the caudate lobe. And you can also see venous drainage, separate venous drainage indirectly into the inferior vena cava. And supposedly that drainage here is what helps to protect the caudate from other diseases.

Another thing you should know about the caudate is that it itself can look like a mass. Sometimes we call that a pseudomass. Here's a section of the liver, and it looks like there's a mass in the caudate. So I would caution you, this is an artifact. If you ever think you see a mass in the caudate, ask yourself first, are you sure that that's not a pseudomass?

What happens with the pseudomass? The ultrasound beam comes through the porta hepatis structures and becomes attenuated. So it partially drops out at giving it the appearance of a hypoechoic mass. If you move off of this porta hepatis and come in with the beam from different angles, you'll see that this is not truly a mass. That's why it's a pseudomass.

Also, the caudate lobe can become enlarged, especially with cirrhosis. We can actually measure that this is described in the literature, and the caudate is enlarged when a certain ratio of the caudate to the right lobe is enlarged. So what we would do, we would take a transverse section of the liver. We would take the medial margin of the caudate and the lateral margin as a lateral margin of the portal vein that we would measure as the width of the caudate lobe, and the rest of it is the width of the right lobe. Then we would take a ratio of C over R or caudate over right lobe. And if the ratio is over 0.65, that becomes an enlarged caudate. If the ratio's over 0.73 or so, that's very specific for cirrhosis of the liver, but you have to have the whole transverse scan on one picture. It's easier to do on CT.

Lobar and Segmental Anatomy

Now that we've talked about the hepatic and the portal veins, this leads us into the basis of modern lobar and segmental anatomy. This is the basis of surgical procedures. Nowadays, this is the reason why surgeons can go in and remove a subsegment of the liver, let's say a metastasis in a subsegment and not harm other parts of the liver. This is possible because of now our understanding of this lobar and segmental anatomy.

We've already told you that hepatic veins drain peripherally, so they are interlobular and intersegmental, therefore, we use them as dividers. Portal veins feed the segments centrally. So they are intralobular, intrasgmental, and we use them to name the segments.

So here we'll start with the hepatic veins as dividers. Here's a transverse section high in the liver, and we see the three hepatic veins coming together at the vena cava. The middle hepatic vein divides the liver into right lobe and left lobe. The left hepatic vein divides the left lobe into medial and lateral segments, but this only occurs in the high parts cranial parts of the liver. That's where the hepatic vein is. The right hepatic vein divides the right lobe into anterior and posterior sections.

Okay, so now we have right and left lobes divided. Now the portal veins, they feed the segments. We name the segments and they define the segments. Okay, so here we have a portal vein with bright walls. The main portal vein just came into the liver and immediately divided into a right portal vein, which is rather short because it suddenly splits into the anterior segment and the posterior segment. Okay, so this is the division of the right portal vein. So here is the right anterior segment, and here is the right posterior segment of the liver. And notice here's our right hepatic vein, and here's our middle hepatic vein. This plane of separation, middle hepatic vein in line with the inferior vena cava is our divider of the liver into right lobe and left lobe. And the right lobe is further subdivided into anterior and posterior segments.

The left lobe has its own divisions. Now here, after the vein split, the main portal vein, the left portal vein has a longer course. It travels towards the left lobe and suddenly takes an abrupt anterior turn. This is the only part of the portal system that suddenly aims anteriorly. Okay, that's the umbilical segment of the left portal vein, and it sends off lateral branches and medial branches. So this would be the medial segment of the left lobe, and these are lateral segments of the left lobe. This is used as a divider. This is the only part of the portal venous system that is used as a divider. I told you hepatic veins are dividers, but this is the only part of the portal system that's used as a divider in the midsection of the liver.

Okay, that's our division of middle hepatic vein dividing right and left lobes. So here we have our subdivisions on very well subdivisions in this case of the left lobe. I've already mentioned three. I'd like to put them all together for you. So we have dividers of the left lobe into medial and lateral segments, high up on high sections. It's the left hepatic vein that divides the left lobe into medial and lateral segments in the middle of the liver. It's the umbilical segment of the left portal vein, which divides the liver into medial and lateral segments and lower down where there are no big veins. We have the echogenic falciform ligament coming in and the umbilical fissure dividing the left lobe into medial and lateral segments. So superior, mid and inferior parts.

Another point that I'd like to bring up here is about the division of the main portal vein, precisely where the main portal vein comes in and splits right in that line here. We can use that as another anatomic divider of the liver. If we look at the liver frontally or on PA, we'll see that that part of the portal vein divides the liver into superior and inferior segments. However, so that's on coronal sections. If we look transversely, we slice up the liver and we find that division in the middle of the liver that will divide further into anterior and posterior segments. So the same vein, it's a tubular structure can divide things into superior, inferior, as well as anterior and posterior. So it becomes useful.

All of that put together helps us subdivide the liver into subsegments, which is useful, very useful for the surgeon because if we can place a lesion in a specific segment, the surgeon can then go after that lesion and remove it without harming other vascular supplied segments of the liver. This is the basis of the Couinaud system, a French system that divides the liver into eight segments.

If we look at the liver from the front, this would be the left anterior lateral segment. Behind it would be the left posterior lateral segment. Way in the back is the caudate lobe. That's always segment one in any system of classification 'cause it kind of stands alone. So we get it out of the way. Then we see the medial segments. We have a superior and inferior medial subsegment. And when we get to the right lobe here, we have anterior superior in blue, and we have anterior inferior in purple for you to see the back. I've rotated this liver slightly. So here's anterior superior, anterior inferior. In the back is posterior inferior and posterior superior. These segments are labeled 5, 6, 7, and 8. It's kind of an unusual system. It kind of twists around like a figure eight. Nonetheless, each segment has a number.

I don't think that you should learn all of these segments with numbers because you have to know what your surgeon uses. Your surgeon may not use this classification, but if you divide and explain that it's left posterolateral or right posterior superior, they will know then which part of the liver the lesion is in.

So here's a little quiz. Name the subsegment with the cyst, okay, this is a transverse scan of the liver. So where would you place this cyst? What subsegment? This is transverse and here's a sagittal scan. Okay, well, I hope that you were able to see that this is the middle hepatic vein. So this is in the right lobe, and this is the right hepatic vein. So that's in the anterior segment of the right lobe, and it's up high by the large hepatic veins. So it's in the anterior superior part of the right lobe, which is segment eight. And that is confirmed here on the sagittal where this cyst is high up sagittal rather than in the lower parts of the liver. So then you can precisely locate this lesion.

Doppler of Hepatic Vessels

Let's look a little bit at the portal veins. For this, we have to talk about the doppler a little bit because nowadays we do more and more Doppler. In a normal main portal vein. We have continuous forward flow. The liver is always available for detoxification of substances. Anything that you eat, anything, any breakdown products from the spleen, the gut, et cetera. So it's constant forward flow with a low velocity. If you did velocities, usually they're 15 to 28 or 30 centimeters per second. The flow is into the liver shown here on this colored doppler, red means flow towards. So we have flow towards the liver. It's an undulating pattern, which reflects respiratory variation and may reflect cardiac variation. It's a slightly turbulent, rough, low rumble kind of flow. That's because it's located between two capillary beds between the mesenteric venous system and the hepatic venous system.

What's abnormal, well abnormal is when that flow becomes too pulsatile. It may then start resembling hepatic vein pulsatility, and that would mean that there's elevated right heart pressures and that there's transmission of pressure through the sinusoids into the veins. We can see this with tricuspid regurgitation. We can see it with moderate to severe right heart failure or pericarditis. The exception would be in the young child where the liver is so soft and pliable that it can actually transmit cardiac pulsations and central venous pulsations from the heart.

Here is an abnormal pattern of a main portal vein. Suddenly it becomes too flat, very flat and continuous flow with loss of that undulating pattern. And that's what we'd see with cirrhosis and hepatic fibrosis where the liver becomes stiff and we lose that undulation.

Hepatic Artery

The hepatic artery typically has a very rapid systolic acceleration. It's a nice arterial pattern. It has continuous forward flow of blood into the liver throughout the cardiac cycle. So it has a low resistance pattern. In other words, fairly high diastolic flow because blood freely enters the liver. It is always in the same direction as the main portal vein flow. So on color doppler these two vessels, the artery and the main portal vein are always the same color. So if you set your color map with red meaning towards the transducer, both will be red. If you turned it blue as meaning towards the transducer, both should be blue, but you should not have one red and one blue, because of course, this has nothing to do with oxygenation, it's direction.

It's also interesting that the portal vein and the hepatic artery sort of have a mutual understanding between themselves. The portal vein carries 70 to 80% of the blood into the liver, whereas the hepatic artery only brings in 20 to 30% of the blood flow, but the artery brings in the fresh oxygenated flow. And the portal vein brings in deoxygenated flow from the mesenteric system. However, it's carrying a lot of flow and there is a certain homeostatic mechanism between the portal vein and the artery. So if the portal vein flow decreases, there's a signal given to the artery to increase blood flow. So as a liver becomes sicker and develops more cirrhosis and blood flow cannot come in through the portal system, the arteries tend to enlarge to bring in more flow.

Okay, so you saw the normal waveform. Now here's an abnormal waveform. The waveform becomes abnormal when the resistance becomes increased and diastolic flow drops. So we see such a pattern after eating postprandial. We also see this with portal hypertension, more resistance in the liver, and more importantly these days transplant rejection. We will pay attention to the arterial waveform.

Now another way that the artery has abnormal doppler is post liver transplant. That's when it becomes important to us. If we see a tardus parvus waveform after liver transplant, this is an abnormal finding. We would see low upstroke and a fairly low velocity, which means that proportionately the diastolic flow is elevated. So we have a prolonged systolic acceleration time. And then this tardus parvus waveform. What it means is that there is a hepatic artery stenosis anastomosis. There's a anastomotic stenosis postoperatively. So we are not seeing the flow through the stenosis itself, but we are seeing the flow downstream from the stenosis when the flow has lost energy and it's trying to relain and is weak. And that's why we get the tardus parvus syndrome. So we don't actually see the stenosis, we just see the effect of the stenosis downstream in a transplant.

Hepatic Veins

Now let's look at the hepatic veins. Normally, the hepatic veins drain towards the heart. That's why they're registered here in blue, away from the transducer. And on the spectral, they are also registered away, usually below the baseline, towards the transducer where we have systole diastole, but we have above the baseline when we have the atrial kick. So we have systole, diastole kick, systole, diastole kick, the normal doppler here.

The reason for this pulsatility is because it reflects respiratory phases and variations in central venous pressure that is transmitted from the right atrium. It also reflects the compliance of the liver parenchyma giving us this phasic waveform, systole diastole kick.

Be careful though, because deep inspiration or Valsalva may reduce this pulsatility and dampen it causing you think there's a problem. So the waveform becomes abnormal when we lose that phasic flow. When we lose that, we know that there's elevated right heart pressure, we lose the oscillations or the amplitudes, we can actually lose the atrial kick. We lose that first, and then the whole waveform starts to be more dampened, eventually turning into a monophasic abnormal waveform that is flattened and actually resembles a portal vein flow. We call this portalization of hepatic venous flow. So it should be a nice pulsatile pattern. And all of a sudden now it's flow. It's because the liver is stiff, the liver's non-compliant and does not allow this wave to be reflected in the vessels.

Sonographic Liver Patterns

Now let's talk about sonographic liver patterns. There are basically three patterns in the liver, the normal pattern, the centrilobular pattern, and the fatty fibrotic pattern. We already discussed the normal pattern. Now there's the centrilobular and the fatty fibrotic.

If you look at it closely, this one has too many portal vein walls. This one doesn't have any. And let's talk about the reason for that. In the centrilobular pattern, what happens is the liver is edematous so that the parenchymal cells, the sinusoids, the hepatic cells become edematous increase in water, drop their echogenicity, okay? And that makes the portal vein wall stand out, giving it a starry night appearance. So you have these bright walls standing out in a dark background of the night sky. So what we see, we see increased brightness of the portal vein walls, and we seem to have more portal vein walls. Now, the liver does not make more portal veins, it's just that we see them because now we have more contrast.

This pattern is seen with acute hepatitis, also seen with the acute right heart failure. You may see it with infiltrative diseases of leukemia and lymphoma. We used to see it with toxic shock syndrome, but we don't see that much anymore, and we can see it with 2% of normal cases. And the 2% of normals are usually the young thin adolescents, maybe 15 to 20 years old. They're so easy to scan and see so well that they look abnormal, and that's easy to tell. The patient is healthy. There's no liver function test abnormalities. So those would be normals. Beyond that, we have to be cautious and rule out liver disease.

I would like to bring up fulminant hepatic failure because this is something that's very serious, but could easily be dismissed or misdiagnosed. You'll not see this often, but when you see this, you should think of fulminant acute hepatic failure and liver necrosis. What you'll see is areas patchy areas of decreased echogenicity with prominent portal vein walls, and areas that look normal. They look echogenic, but they're actually normal areas of liver. You look back at these, this is the starry night pattern reflecting acute edema or necrosis, and these are areas of normal or regenerated liver, so they come in patchy areas.

This is a case that we recently had of a 22-year-old man who came in with jaundice. And we saw areas of the liver that had increased portal vein brightness, and we thought that that looked like acute hepatitis. Yet other areas of his liver seemed to be normal. He did have jaundice and he was not that sick. However, his bilirubin was close to 30, eventually got up to 30 in the hospital, and he became so sick that he ended up with a liver transplant. So what happened in this case? It turned out that he was using herbs, certain herbs for bodybuilding, and apparently developed some kind of toxic effect from these herbs, and developed liver failure and ended up with a liver transplant.

I have seen such situations happen. One case was a sulfa drug reaction, a woman who was on sulfa drugs for bladder infection who came in as an outpatient and had this appearance. So we thought that something was very unusual and wrong. We sent her to the emergency room, and after I followed her up in three weeks, I found out that she too went into liver failure and had a liver transplant from sulfa drug reaction.

Another patient that I had that I recall with this pattern was a 34-year-old woman who was weak, a little bit jaundiced and in the outpatient setting. And I thought, gee, this liver, something's very wrong. I sent her to the emergency room and on follow up, I found out that within 24 hours, she was dead. Autopsy revealed that she went into heart failure. She had lupus myocarditis and lupus hepatitis, and developed this acute fulminant failure. So these are unusual cases nonetheless, serious, and we should not dismiss such an appearance. If you're not sure, if it doesn't look like it matches the clinical picture, we should send the patient right away for evaluation.

Fatty Fibrotic Pattern

The fatty fibrotic pattern is opposite. We have increased echogenicity of parenchyma. There's some kind of infiltration with fat or fibrosis going on in the liver, which increases the echogenicity high enough that it matches the portal vein walls and the contrast is lost. Therefore, we do not see the echogenic portal vein walls in this pattern. We look at the echogenicity, that's increased, but then we have to look now at the echo texture. It could be a smooth homogeneous echo texture of the parenchyma, or could be heterogeneous or coarse. Sometimes we see sound attenuation and this type of pattern is usually seen with fatty infiltration, but also seen with chronic hepatitis and cirrhosis.

So here's the fatty fibrotic pattern with the homogeneous echo texture. Here's the fatty fibrotic pattern, loss of portal vein walls with the heterogeneous pattern. Notice we almost see little tiny rounded masses throughout a little bit nodular. That's what gives it this heterogeneous appearance.

Let's look at the fatty liver. Fatty livers are of this pattern, echogenic loss of portal main walls when it's a very pronounced case. There's so much attenuation that we can't even image the hemidiaphragm as we have in this case. We've tried to increase the TGC curve posteriorly, and we cannot fill in with echoes. Notice how nice and homogeneous this pattern is.

Now, fat can do two things fo we can have focal fatty infiltration and we can have focal fatty sparing. Okay, here's focal fatty infiltration where we have areas of fat. Now, the fat part is echogenic fat, areas of fatty infiltration interdigitating between areas of normal liver parenchyma, and we also can have focal fatty sparing. Here are areas of normal liver not affected by the fatty infiltration. You look carefully, you see little vessels inside. There's no distortion. This is a completely normal little liver pattern, and that's areas of normal liver spared. This can possibly be confused with liver masses, however, they occur in a very typical location around large portal veins, around fissures and subcapsular. So we tend to look in those regions and we look for internal architecture and see that it's not distorted.

Cirrhosis

Cirrhosis has this fatty fibrotic pattern. Now, when we make a diagnosis of cirrhosis, we look for heterogeneous echo texture, so coarse sometimes that it looks moth eaten, and it's from these little islands of regenerated tissue mixed with disease tissue that causes this heterogeneous pattern. The livers tend to be small and shrunken. They have a nodular surface. Often there's ascites to help us delineate the surface. And these are the livers where we can see the enlarged caudate. So if you see an enlarged caudate to right lobe ratio, and if it's over 0.73, that's a 99% specificity for cirrhosis. It's not sensitive, but it is specific.

Here's a cirrhotic liver. Try to imagine what you would see in ultrasound. You see these nodular areas of regeneration all throughout in between are these fibrotic bands, and that gives this nodular appearance. Sometimes micronodular, sometimes the nodules are bigger and sometimes macronodular appearance. Look at these tiny little islands of regeneration inside the liver, which cause vascular channel disruption, et cetera.

So when we see a cirrhotic liver on ultrasound, we then have to right away look for clues of portal hypertension.

Portal Hypertension

So with portal hypertension, the liver is diseased, the liver parenchyma develops resistance to blood flow. This increases the portal venous pressure. Eventually the portal flow will slow down and it will reverse and flow will actually be going away from the liver hepatofugal. And there's then increased risk of bleeding because collateral vessels open up.

The ultrasound findings of portal hypertension include ascites, a dilated main portal vein, splenic vein, or superior mesenteric vein. What is a dilated portal vein? Well, a portal vein bigger than 13 millimeters in diameter, we consider dilated a splenic vein or superior mesenteric vein centrally. When it measures more than 10 millimeters, we consider that dilated. So just a simple measurement. We look for collaterals, splenomegaly is part of it, and various doppler findings.

Where would we look for collaterals? Well, right away the first place to go is the gastroesophageal junction, GE junction. We then can look for a coronary vein, which would be a little branch off the main portal vein or off of the splenic vein. We would look for a recanalized umbilical vein heading towards the umbilicus. We can have gastro splenic vessels. We can have lienal renal collateral. We can have gastro renal collateral. We can have perisplenic, all kinds of retroperitoneal collaterals vessels that we don't usually see suddenly appear. So we try to look for them on ultrasound.

Here is the aorta, the gastroesophageal junction, GE junction and tortuous serpiginous vessels in the region. These would be the gastroesophageal collaterals. Here is a sagittal section through the recanalized umbilical segment, recanalized umbilical vein. And it has flow heading out of the liver towards the umbilicus. Hepatofugal flow out of the liver.

In this image, we see the splenic vein, which is posterior to the body of the pancreas, and it seems to have a branch. We usually never see a branch there, but when we see such a branch, that's a perfect place for a coronary vein. Here's a spleen with large vessels around it up in the left upper quadrant, perhaps these are gastro splenic collaterals. Here's perigastric or perisplenic kind of collaterals. Here's a large spleen with the left kidney, and there's a large tortuous vessel in between a splenorenal shunt.

What are the doppler findings in portal hypertension. Well, let's look at the portal veins. First of all, we're gonna lose the respiratory variation. The waveforms become very, the waveform becomes very flattened. We have a drop in the velocity of the main portal vein, and eventually it may reverse and be on the reverse side. Hepatofugal flow, hepatic veins, hepatic veins start to lose their normal pulsatility. We had systole diastole kick, systole diastole kick, and now all of a sudden it's becoming a very flattened waveform, hepatic arteries. The only thing we'll see is that they can become quite large.

And also notice here on this color image, the hepatic artery is red. The main portal vein is blue. They're opposite colors. The artery and portal vein should be the same color. This means that the artery is going towards the liver. And the vein now has hepatofugal flow. So we can see that as two different colors. You can also see enlarged hepatic arteries in the parenchyma of the liver. And what happens in that situation is in the portal triad, where you have the little portal vein on top of it is dilated. A little hepatic artery now also sits there the bile duct. Usually when we see a dilated duct on top of the portal vein, we see this parallel channel arrangement, but it can also be seen with a dilated hepatic artery. We turn on doppler. One has venous flow, one has arterial flow.

Focal Liver Masses

Now the last segment that I'd like to talk about the liver is regarding liver masses. Ultrasound is excellent in detecting focal liver lesions. We're very specific. We're specific for liver cysts, but liver cysts that are about a centimeter or more because very tiny ones we may not be so sure about. But ultrasound is not good. In differentiating among the different pathologic entities, there are very few ultrasound features outside of cysts that are characteristic of the mass itself. The pathology, we are not good in distinguishing between benign and malignant masses. Triple phase liver CT and MRI are excellent modalities for this, but we are good for picking up a focal mass. And we are also very helpful in the diagnosis, in the proper clinical setting, or good for follow up. And as a guidance for biopsy, we can see simple cysts.

Now this is a classical cyst like anywhere else in the body. A hypoechoic mass, smooth margins, excellent sound transmission. So this is a simple cyst in the liver. What else can be simple cyst? Well, an old hematoma, a hydatid or an amebic abscess, which this is, this is a patient from Egypt who had a solitary cyst and eventually this was diagnosed to be an amebic abscess. A myeloma or a seroma can look like a simple cyst. And if we ever have a vascular structure or if we ever have a cystic structure that looks unusual, not perfectly round, we should always think of the possibility of this being some type of vascular structure, like an aneurysm or some unusual fistula like arterial portal, venous fistula or portal to hepatic vein type of a fistula.

We can have multiple cystic lesions throughout the liver. Very often these are associated with adult polycystic kidney disease or the autosomal dominant polycystic kidney disease. We could see multiple cysts with Caroli's disease or ADPKD disease as was in this case. We can have multiple bile cystic lesions throughout the liver that are actually choledochal cysts, the type four and the type five. Type four has the dilated bile duct. Type five has a normal bile duct. But we can see these structures, cystic structures throughout the liver. If we look at them closely, we will realize that they actually connect. And these are tortuous tubular structures, but many times they just look like collections of cysts.

This is a reminder for you of the choledochal cyst. The type one has a dilatation of the bile duct. The type two has a little diverticulum, a little cyst off the bile duct. Type three has a little choledochal cyst protruding into the duodenum. Type four has dilated biliary ducts throughout the liver, looking like small cysts. And it also has an associated fusiform dilatation of the common bile duct. And type five or Caroli's disease has the dilated intrahepatic ducts, but no dilatation of the common bile duct. So these types you can see, and it's these two that would have dilated cystic type structures in the liver.

Complex Cystic Masses

Complex cystic masses. What about cystic masses with echoes inside of them? Well, that could be from hemorrhage within a cyst. It could be from infection in a cyst, it could be a hematoma in the liver, could be an abscess in the liver. Notice that there's sound through transmission. So we know that this is of cystic nature. In this case, this was an abscess. It could be a biloma or seroma, could even be a large biliary cystadenoma or could be a cystic or necrotic degeneration within a metastasis or a malignant tumor.

Liver abscesses sometimes cause trouble in diagnosis. A liver abscess when it has fluid and debris is fairly easy to spot. But when it has bubbles of gas or pockets of gas, that sometimes may shadow out the back wall of the abscess itself and may cause confusion in its appearance.

Here's another way that an abscess can confuse us. An abscess completely filled with pus can be echogenic and sometimes isoechoic with the liver and it may actually mimic liver and you may not recognize it, but your eye then would catch some effect on a vessel. Perhaps you may catch an edge effect from the curved surface and you would eventually realize that there is an abscess here within the liver.

This is a fairly characteristic appearance. If you saw a cystic mass in the liver and you saw this kind of folding thin membrane referred to as the lily pad sign, this is the sloughed internal membrane folding in upon itself very characteristic of an echinococcal cyst. If you see this, you may be the first one to suggest this diagnosis. Patients travel these days to various parts of the world and may bring back a souvenir, an echinococcal cyst. Nobody may think of it until the characteristics sonographic picture is presented.

Other complex cystic masses can occur. We can have benign, we can have malignant. This happens to be metastasis that are complex cystic lesions. This one is looking in echinococcal cyst with internal debris, this one metastases. So we can't really tell. There's nothing specific. So that's why I'd like to make just a list of hypoechoic masses in the liver.

Nothing very specific about these. We can have an abscess. We can have an adenoma, focal nodular hyperplasia, a hemangioma and unusual atypical hemangioma, focal fatty sparing micro abscesses. They can be hypoechoic. It could be a malignant metastasis, hepatocellular carcinoma or lymphoma. We can't tell. This happened to be a case of focal nodular hyperplasia. Proven. And this was proven by MRI. We see in the literature that focal nodular hyperplasia has a central scar. However, this is not diagnostic. It's fairly characteristic, but it is not diagnostic. And here's why I'd like to show you. Here's a lesion with a central scar. And this was a hepatocellular carcinoma. This was a lesion that seemed to have a central scar and this ended up to be a giant hemangioma. So you see, even that central scar is not characteristic enough to be 100% diagnostic.

Homogeneous Hyperechoic Masses

We also have lesions in the liver that are homogeneous and hyperechoic, and most of the time they are hemangiomas. Both of these are, but we have to be very careful. There are other lesions that can look exactly like this, that are not hemangiomas, hemangiomas when they are found incidentally in asymptomatic patients. And in a young patient, a patient under 40 while such a lesion, we can call a hemangioma if it's under three centimeters. But if the patient is older, beyond 40 or if the patient has any other medical illness, we have to then prove this to be a hemangioma.

Let me show you some atypical hemangiomas. This is hemangioma, atypical heterogeneous. This one has some cystic spaces. This one is not totally hyperechoic. This one is hypoechoic and has some sound transmission. All of these are hemangiomas, but they're not typical.

Now let's look at something hyperechoic. What's the differential of a hyperechoic lesion in the liver? Well, we all know about hemangioma, but it could possibly be an abscess. It could be an adenoma, could be focal nodular hyperplasia. It could be focal fat, could be a hemorrhagic cyst and it could also be something malignant. Could be a metastasis, could be a hepatocellular carcinoma, could be lymphoma. Not very specific. All of these are unusual, but this one happens to be a thyroid cancer metastasis. So you see nothing is 100% in the liver.

Multiple Solid Masses

Now when we talk about multiple solid masses in the liver, the differential diagnosis is metastasis, metastasis, metastasis. But there are other pathologies that can mimic this. That can be just the same. Usually we would say metastasis and we would want to have a history to see what's going on. But it's still, even in this case, not 100%. We can have regenerating nodules in a liver in cirrhosis like this patient had. And this patient has lymphoma masses within the liver. So even solid metastases are not a hundred percent.

Here's another patient with multiple focal hypoechoic masses, and this was multiple atypical hemangiomas. And this one with small hypoechoic masses was micro abscesses in an immunocompromised patient. So multiple hypoechoic solid masses is not always metastatic disease.

Some metastases are calcified and we usually think of them as coming from colon cancer, but there is a whole laundry list of other cancers. We can see calcified metastases with ovarian cancer, breast cancer, stomach cancer, pancreas, osteosarcoma, mucinous sarcoma, chondrosarcoma, teratocarcinoma. So certainly not a specific appearance.

What's very useful with sonography is that when we're not sure we need a tissue diagnosis, we can just guide a needle straight into the mass and get a biopsy or provide drainage if it's an abscess. And that's extremely useful.

Before I close, I just would like to remind you that when you have a case of liver metastases, you should always think a little further to see are those metastases causing any complications such as segmental biliary obstruction? You should double check the vessels. Are the metastasis invading vessels, is there invasion of the portal vein is there invasion of hepatic veins? This is a patient who has hepatocellular carcinoma in the left lobe and tumor has grown into the main portal vein, tumor thrombus. You should look for necrosis, maybe a hemorrhage or some kind of super infection. These are all possible complications of liver metastases.

Conclusion

In conclusion, we have discussed the appearance of the normal liver. We've talked about normal and abnormal doppler patterns of hepatic vessels. We've covered diffuse liver disease patterns. We've talked about portal hypertension and discussed focal liver masses. Thank you for your attention.