FibroScan, Explained

Dr. Mitchell Rothstein goes over the FibroScan, a liver scanning technology that produces fast and cheap measurements of liver fat content and fibrosis. Dr. Rothstein reviews what the FibroScan is, how it works, the process of getting a FibroScan, and what the results mean. The doctor explains when you should get a FibroScan, what to expect from the process, and the accuracy compared to invasive liver biopsies.

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Chapters

• 0:04 What FibroScan Is And Why It Matters
• 0:20 Shear Waves, Elastography, And Fat Signals
• 2:35 The Liver Disease Surge And MASH
• 4:04 Live Demonstration Of The Scan
• 6:41 Interpreting CAP And KPa Scores
• 8:57 Reversal, Treatments, And Follow‑Up Value

Transcript

Dr. Mitchell Rothstein: 0:04

Hi, I'm Dr. Mitchell Rothstein, and I was wanting to talk today about fibroscanning and how we're using it in clinical research and how it's being used in clinical medicine in general, what it is and how it works. And fibroscan has actually been around for about 15 years. It's a first cousin of ultrasonography, and it uses wave physiology for us to help determine the amount of damage in the liver as well as the fat content of the liver. And it does this by measuring shear wave technology. And the way fiber scanning actually works is it creates- we have a device, a probe. In this case, we place the probe against the chest wall next to the liver, and we use the probe to create a pulse vibration. That vibration travels into the liver and then bounces back. And then there's two aspects to that vibration waveform that we're looking at. One is how quickly that waveform comes back from the liver, and the second part is how much of the waveform comes back from the liver. The first part, the speed with which it comes back, is a measurement capacity of organs in the body called elastography, the elastic properties. The more elastic an organ is, the more of the waveform is absorbed and slowly returned. And as fibrosis and damage occurs to the liver, the liver stiffens. That causes the waveform to come back more quickly to the transducer probe, and we measure that speed. So that speed then reflects indirectly how much damage is in the liver and how much fibrosis has occurred. The other aspect of that waveform that we look at is how much of the waveform comes back. Fat is known to absorb waveforms, and so as the waveform is transmitted back and the liver becomes fattier, less and less of the waveform comes back because more and more is absorbed. So those two measurements, one the stiffness of the liver, and two, the fatty, the uh fatty content of the liver is what's expressed in what you'll see on the probe in just a minute. We had a patient and a technician who were nice enough to want to be part of this podcast video and we'll show you how that actually works. What that information then tells us is it gives us a rough idea of how much damage has been going on in the liver. And liver disease in society right now is a growing, growing problem. We know that compared to 50 years ago, the amount of people that suffer from what we used to call fatty liver has at least doubled, if not tripled. It's part of the obesity epidemic that's in the entire world. Right now, the estimates for world population of the prevalence of fatty liver, or the new term is called MSALD, which is metabolic associated steatohepatitis or MASH, is about 40% in the general population. And we know that if untreated of that 40%, 10% will continue to progress from that liver damage to cirrhosis. And it's a huge, huge medical problem in terms of care as well as cost. In fact, metabolic-associated liver disease, what we used to call fatty liver, is now the leading cause for liver transplants in the United States. It used to be hepatitis, an infectious disease, now it's a metabolic disease. And then we also know that people that have MASH, metabolic associated steatohepatitis, have a host of other medical problems. They die more quickly from cardiovascular disease. We know that people with diabetes, 70 to 80 percent of them will also have problems with their liver. So this is a common problem, and we need to kind of get our hands around it so we can follow and treat these patients. So let's go over and see what the actual procedure of a fiber scan looks like in real life, and then we'll come back and talk about how we use that information. Now is the actual fibro scan procedure, and our fibro scanner, Marijana, is holding the probe against the patient's uh wall uh skin wall in order to visualize the liver, and if we can just show them what the probe looks like itself. And when the probe is activated, it causes a little pulse on the end of the probe, which is almost like the sensation of having your finger flick against your chest, and that creates the sound wave that then we're recording. So let's go back into position. And Marijana's positioning the probe in between the patient's ribs to get a picture of where the liver is. When she activates the probe, it creates that flick, which is a waveform, and in this case it's actually looking pretty good in terms of finding the liver itself. And the shear wave that's produced by that bounces back and is recorded in terms of the it translated into a measurement that records the stiffness of the liver. And that's related to how quickly the waveform bounces back here. So here we have a beautiful waveform. This is the sheer waveform, and this is then representative of the speed with which the wave hit the liver and came back, and that produces a measure of stiffness. As the liver becomes stiff with disease, that waveform bounces back more quickly. As opposed to, if you think about it, if you had a tennis ball and took it out and tried to bounce it off the sand at the beach, it wouldn't bounce that well back. But in here on a hard floor, it comes back quickly. The faster that waveform comes back represents stiffening of the liver. The other thing that we look at is how much of the waveform comes back, and that's this CAP score. And the CAP score relates to the fat content of the liver. As the liver accumulates fat, more and more of the waveform is absorbed by the liver and less comes back, and that is then translated into this cap score, which is a score that indicates the fat content of the liver. So those are the two major measurements we're looking at when we have patients undergoing fibrous scan. One is the KPA or the stiffness score, and the other is the CAP score, which measures the fat content of the liver. So now that you've seen an actual non-invasive rapid fibro scan in action, let's talk a little bit more about the information that we glean from that. The CAP score, the controlled attenuation parameter, which is the measurement of fat in the liver, gives us a guideline as to how much fat is actually accumulated. So, as we said, the less of the waveform comes back means the more of the waveform has been absorbed by fat in the liver. And as the CAP score gets higher, it reflects a higher fat content in the liver. It's an inverse relationship. A lot of people will have a little bit of fat in their liver, but once that content gets above about 10 or 15%, it starts to cause inflammation in the liver cells that then leads to fibrosis. So the CAP score is one part of it, and we grade the CAP score based on the percentage of fat, as we said, on a scale of 1 to 3. But the more important part of this then becomes is how is the liver reacting to the fat that has accumulated? So there are people that will have fat extra fat in their liver that don't develop fibrosis and scarring, but most people will to some degree. And as we said before, about 10% of the people that develop scarring, if the if it goes on untreated, will progress to cirrhosis and the complications associated with that, and potentially ultimately liver failure or hepatocellular carcinoma. So we want to identify those people that have fat in their liver and are showing this inflammatory fibrotic response, and that's this KPA score. So as we said, as the liver becomes stiffer and that waveform gets reflected more quickly back to the ultrasound probe, this fibrosis score gets higher and higher. So we use a combination of the CAP score, the fatty content of the liver, and this fibrosis score to grade people as to where they are on their journey of mash or metabolic associated steatohepatitis. Once we have this information and we've graded people as to their fat content and the fibrosis or inflammatory content of the liver, what do we do about it? So the first line is that we want to do things to reduce the fat if possible, and the way we can do that is by weight loss. We know that most, if not all, of the changes that occur in MASH patients are completely reversible before they enter the final stages. So if we have patients with moderate fibrosis and they cut down on their caloric intake and their fatty liver starts to diminish, they their fibrosis can diminish as well. Over the last couple of years, we've also found that these medications that are now used quite commonly for obesity seem to also be effective in reducing fatty liver and MASH. And there also are individual products that have just come on the market that help reduce the fibrosis in fatty liver. One of them is marketed as it's actually a thyroid analog that attacks only the liver cells, that helps metabolize the fibrotic tissue and can help reduce the inflammation and fibrosis as well as reverse it in many patients. But this is a common problem. We're seeing it more and more frequently. Many of us are at risk. In fact, we know that 40% of the adult population in the United States has some form of fatty liver somewhere along that grade line, so it's important to be screened. And once you're discovered to have it, not only can we then take actions to try to eliminate what's causing the problem, but we can also monitor the disease as it goes on. We can also use fibro scans in people that have other forms of liver disease, like viral hepatitis and how they're responding to therapy and whether or not that needs to be looked at as well. So fibro scanning overall is a rapid, painless, non-invasive test that gives us a wealth of information. We know the specificity and sensitivity of fibro scans compared to liver biopsies. It's about 80%. So it's not like having a liver biopsy, but it's almost as good and it's non-invasive. And if we have a way of following people in their liver disease without having to take biopsy samples from them on a regular basis, that's where this tool comes into our favor in terms of our ability to help patients in their pathway.