Thank you for joining us for this webinar. I really hope that you find it useful. Today, I'm going to talk through how to do an autosonnographic assessment of the equine abdomen.

This is a technique that usually takes anywhere from 15 minutes to an hour, depending on how compliant the horse is, how much experience you've got with the technique, how many abnormalities are present, and how complicated they are to assess. Abdominal autogenography can be useful in a wide variety of cases, including the ones listed here on the slide. And there are two main ways of approaching an abdominal ultrasound.

One is a comprehensive and complete assessment of the abdomen, and one is a flash scan, which is a quick scan that can be done in about 10 minutes. And that's targeted specifically at the assessment of the acute colic. I'm not going to talk any further about that technique today.

I'd like to talk about a more comprehensive assessment of the abdomen. The reason being is that because abdominal ultrasonography can be used in such a wider range of cases than simply the acute colic, I think if you Limit yourself to that technique, although it is a useful technique for the purpose that it's designed. But you can be missing out on quite a lot of diagnostic information and limiting the cases in which you can use it.

So I'm hoping that this approach will be of more use to you. Abdominal autonography does take practise. I'm hoping that this presentation will provide you with a, a solid foundation in the Theory of the approach and understanding of the images that you'll obtain.

But if you are new to abdominal totinography, then it's likely that you would benefit from some practical support as well to help you get off the ground with it. There are 3 parts, in my opinion, to scanning the equine abdomen. One is obtaining useful diagnostic images of the organs that you'd like to assess.

The second part is being able to recognise normal in a wide variety of patients, and therefore recognise abnormal when it's present. And then the 3rd part is deciding what to do about the abnormalities that you find. So the 3rd part, we're not going to cover today, but I hope I can cover the 1st 2.

So the aims of the presentation will be to give you an overview on how to obtain a useful set of diagnostic images of the equine abdomen, to gain familiarity with normal and to demonstrate some examples of abnormalities. The tolerance by horses for abdominal ultrasonography is variable. Many tolerate it very well.

Others less so. Particularly, I think the inguinal regions, as when you're applying cold isopropyl alcohol to those sensitive, poorly haired areas, it can be quite irritating to them. So the amount of restraint restraints required is variable.

In some cases, simply someone holding the horse will be adequate. In other cases, sedation or twitching will be required. I do think it's worthwhile if it's not being well tolerated, even though it's not an invasive procedure, as as well as not being safe, it's also really quite distracting when you're trying to dodge a foot whilst carrying out this assessment.

The amount of patient preparation required will be variable. If you're fortunate enough to be presented with the horse in the top picture, then simply applying isopropyl alcohol to the hair and skin is likely to be adequate. If, however, you're presented with the patient at the bottom, particularly if it's an acute colic that's been rolling in mud, then you're highly unlikely to see anything at all without quite extensive preparation.

And in that case, you really will need to clip off the majority of the hair on the abdomen if you're going to carry out a comprehensive assessment. And after that, I'd recommend scrubbing that area to get rid of the dirt and grease, followed by spirit application, wiping and further spirit or or isopropyl alcohol application. Don't be shy with the isopropyl alcohol application.

There are times when cases take a while to scan when you might use a litre of this. So if you're going out to see a horse in the field, to perform a scan, then I'd be sure to take plenty with you. You'll need a 3.5 megahertz curvilinear transducer, also known as a sector probe, to scan the abdomen of the adult horse.

If you tried to use a linear high frequency probe that you might use for tendon scanning or reproductive work, you just won't get the depth to assess the organs that we need to see. For each image that we acquire, we need to ask ourselves, have we got the right depth, focal point, and gain in order to get the best image of the areas that we wish to assess. So, before we move on to the details of the specific images, I'd just like to give you an overview of what we're going to cover and how we're going to approach it.

I don't think it matters what order you scan the abdomen in, but I think it is important to have a system and to stick to that system so that if you're tired or distracted or spot something interesting along the way in the scan, at least you always get to the end of the scan and find that you've covered everything. So I like to start at the left cranio ventral abdomen, move along the left side. From cranial to cordal, and then move around to the other side of the horse, and then move from caudal to cranial.

So that would mean starting with the stomach, as highlighted in red. I'll just mention that these coloured patches that I'll display on the side of the horse correlate to the windows. So the area on the side of the horse where we're going to put the probe, they don't necessarily equate to where the organs sit, as sometimes they'll be viewed from different angles and different parts of the abdomen.

So after we've viewed the stomach, we'll move on to the left cranio ventral abdomen. So the nephrosplenic region. Then the spleen Then the inguinal region, then the left ventral abdomen, particularly the left ventral colon, and then the plural space.

I'm a believer in the benefits of adding ultrasonography of the pleural space to an abdominal ultrasound. This is for a number of reasons because sometimes horses may have both abdominal and thoracic pathology. Sometimes we might think they're going to have abdominal pathology, but actually they have thoracic pathology.

And although just scanning the cranio ventral pleural space gives us limited information, in many cases it will give us an indication as to the likelihood of a subsequent thoracic scan being useful to us. On the right of the horse, we'll start with the nephrosplenic region. Then we'll move on to the secum, then the inguinal region, then the liver and right dorsal colon, which are seen through the same window.

Then the ventrum, then the right cranio ventral abdomen, which will mostly consist of the right ventral colon and then the right pleural space. So when we scan the stomach, we're going to move across a number of intercostal spaces in the left cranio ventral abdomen, starting in the area where the star is. And when we scan in this area, we're going to keep the probe between the ribs, so in each intercostal space, and we're going to move from dorsal to ventral.

And during that, we'll also angle cranially and then cordially. So we'll initially put the probe at the dorsal aspect of that most cranial red line, looking into the abdomen. We'll angle.

Slowly cranially and slowly cordially and then we'll move further ventrally angle slightly cranially and slightly cordially to view that area and then repeat the process for ventrally and we'll repeat that process across each of those relevant intercostal spaces. It's important not to angle the pro to change the angle of the probe in a clockwise or anticlockwise direction. Otherwise, you'll find that the rib interferes with your ultrasound beam, and you'll have an area of your image that you can no longer see into the abdomen.

Another important point when using a sector probe to scan the abdomen is that we always want the centre of the probe to be in contact with the horse. So, that is demonstrated in the bottom left image here and We would expect to see a full normal field of view in our ultrasonographic image. The image on the bottom right demonstrates a probe where the dorsal half of the probe is no longer in contact with the abdominal wall, and therefore, we'd expect to see an area of image loss where we were no longer generating an image in that area.

And that can be seen in the ultrasonographic image at the top right of the picture. The convention in the UK is for dorsal or cranial to be on the left of the image. So all of the images in this presentation are presented in that orientation.

The normal stomach always contains at least a little bit of gas, and because the ultrasound beam can't pass through that gas, it will be reflected, giving the stomach a hypoechoic contour. This is also true of the colon, so there are a couple of features that we're going to look at to help us differentiate the stomach from the colon. The most useful one I think is the splenic vein.

The gastrosplenic ligament keeps the stomach and the spleen adjacent to each other, and the splenic vein will always be orientated towards the stomach. It can be normal to see some layering in the wall of the stomach, and that is not true for the colon, unless the colon is abnormal. The normal stomach is visible over 5 intercostal spaces, and we talked about at each intercostal space angling the probe cranially and cordially.

If, for example, you look straight across the horse from that intercostal space, and you can see the stomach, then you would count that intercostal space. But if you have, if you have to angle cordially in order to see the stomach, then you wouldn't count that intercostal space in those numbers. I just wanted to bring your attention to a normal variation, which if you're not aware of it, could potentially be mistaken for pathology.

And this is the folding that can develop in the wall of the stomach over the greater curvature. The most common abnormalities we would see ultrasonographically for the stomach would be distention, either due to fluid or distention without fluid. When we have distention due to fluid, that can be either because of reflux or because of significant water consumption.

That's not something we would usually see following a normal drinking episode, but if the horse has consumed a particularly large amount, then we may still see fluid within the stomach. The stomach can be distended without the presence of fluid, and that would usually be either gas distension, or if you had an accumulation of ingestor, or if that was severe, a gastric impaction. But because there's most likely to be at least a little bit of gas on top of any ingestor that's there, typically, you can't see into the stomach, just giving it that overall hypoechoic appearance.

I think it's important to mention that unless the stomach is absolutely full of fluid at the level at which you are viewing it, you won't see that fluid because, again, the, the ultrasound won't pass through to the fluid because of the little bits of gas over the top. So it, it can be easy to think that you don't have fluid present there. When actually you do.

So the angling cranially and cordially at each level can help us to cut underneath that gas cap and to see the fluid. But nonetheless, particularly, I think when you first start scanning horse's stomachs, I would always trust your clinical judgement of the horse and also your stomach tube, much more than your ultrasonographic assessment as to whether or not there's reflux, present. Next, we're going to scan cranial to the stomach.

The probe is going to be at the angle of the ribs again. It's going to be pointing straight across the abdomen or slightly cranially. It's only a small area that we're going to scan in this region.

So here we can see the liver. And although most of the liver is visible on the right side of the horse, there is this small part often visible in the left cranial abdomen. And this can be particularly useful because it's helpful to know the ecogenicity of the liver in comparison with the spleen.

And of course, when you're viewing the liver from the right, you can't see the spleen. So, Being able to compare the two in this region can be helpful. Here we have the spleen.

Here we have the left ventral colon. So perhaps you can see why it one might confuse this with the stomach. And this is where the splenic vein comes in again, because you can see that that is, again, directly adjacent to the stomach, helping us to determine which is the left ventral colon and which is the stomach.

I'd like to talk at this stage about colon wall thickening. As in most circumstances where you're doing an abdominal scan, this will be something that you'll want to consider. It can be variable along the lengths of the colon.

So there may be parts where there is thickening and parts where there isn't. And it can also be variable from very mild, barely detectable thickening of the wall to extreme thickening of the wall up to about 4 centimetres. So in this image, we've got mild to moderate thickening of the left ventral colon wall here.

And in this image, we've got severe thickening of the colon wall. This is, in fact, a different part of the colon, but I wanted to put these images together for comparison. You can see that the extreme thickening of that wall has variable ecogenicity.

This is the area, marked by the yellow, but that overall, it's hypoechoic to the colon. I also wanted to draw your attention to an easy mistake to make, which is mistaking the gas highlighted in the interface between the colon and the ultrasound beam and mistaking this for the wall. So that's the area highlighted in red.

So when you've got that thickened wall there as we have in this image, then perhaps you'd be unlikely to mistake this area in red for the wall. But when you have a normal colon in This can be Misinterpreted. So the wall thickening should always be hypoechoic, and the gas cap will always be hypoechoic.

So this is an example of a totally normal colon. Again, the Gass interface has been marked in red, and that could be mistaken for a wall measurement. So I think when you start scanning abdomens, that's just something to be aware of.

Next, we're going to move on to the nephrosplenic region. The probe will be angled slightly cranially and slightly ventrally. It's going to be positioned between the ribs and potentially just slightly cordal to the last rib.

We're going to move from dorsal to ventral in that highlighted area, moving progressively cranially to cover the area we need to see. And each space will be, like we did for the stomach, angling slightly cranially and slightly cordially. You can also assess the kidney further.

In this area by placing the probe higher up on the horse and Angling from dorsal to ventral in a longitudinal manner to see the kidney in a longitudinal plane. So what are we going to see in this area? The left kidney, the spleen, the nephrosplenic space, and possibly some small or large colon, medial and ventral to the spleen.

So here we have the dorsal cranial part of the spleen. On the left kidney. A nephrosplenic space being between the two and dorsal to the two.

Here we have the left kidney again and the spleen again, but slightly more ventrally. And here you can see some loops of small colon, the lateral aspect of which is highlighted in red. And this is just slightly further ventral in that first image.

So what's normal for the left kidney? Unfortunately, it's quite common to gain a low resolution image of the left kidney in the horse. But we should be able to see whether or not the outline is regular, and that's helpful in terms of looking for neoplastic abnormalities or abscessation.

I've put these following notes in in blue because They're here for completeness, but unfortunately, we often can't assess these elements properly because of the low resolution image on the left, but they may be more likely to be useful to us when we obtain a, a good diagnostic image of the kidney on the right. So there should be no discrete areas of differing ecogenicity. We should be able to see some corticomodullary distinction.

And the cortex in a 500 kg horse is approximately 1 centimetre in thickness. There should be no areas causing acoustic shadowing. And no dilated areas.

The left kidney is bigger than the right, and it's different in shape. So this is an image of a horse with chronic pyelonephritis. And you can see an overall increase in ecogenicity and loss of the normal architecture.

This is an image of a renal adenocarcinoma, and you can see that the kidney is greater in size. It has an irregular outline. There are focal areas of increase in ecogenicity, and there's a loss of normal architecture.

This is an image of a horse with unilateral hydronephrosis, and this is due to urethral obstruction by a urethralis. The overall kidneys demonstrated in yellow and the dilated pelvis is highlighted in blue. So what's normal for the spleen and nephrosplenic space?

The spleen should be homogeneous, and it's important to be aware of an artifactual increase in ecogenicity. So if you look at the image displayed here, you'll see that in the centre of the spleen there, it appears to be of increased ecogenicity compared to the areas around it. That's actually an artifactual finding.

And if you were to Alter the angle of your probe. So it looks slightly cranially, look slightly cordially or angle from, or view from a different rib space. You could assess that same area and see whether or not that hyperecogenicity is still present when viewed in a different way.

The spleen should be flat against the body wall. And it often looks slightly rounded dorsally and cranially, and that's normal. Occasionally we see fluid in front of the dorsal and cranial parts of the spleen, and that can also be normal too.

In the nephrosplenic space, we see connective tissue. It may see small small intestine, which most often won't be clinically relevant, but of course, we don't want to see colon. So in this image, we have the spleen and the kidney in the same orientation that we had previously.

But this time we have colon sitting in the nephrosplenic space. And the image you see when you have a left dorsal displacement of the colon can be quite variable. So in this case, there's not significant gas distension of the colon, and we can see that that structure is there when it shouldn't be, but we can still see the kidney.

When the significant gas distension of that colon, often the view of the kidney is entirely occluded. So I'd recommend that you scan the remainder of the spleen. Splenic pathology isn't common in the horse, but when it is there, we want to know about it.

We're going to have the probe at the angle of the ribs again. Pointing straight across the abdomen. And moving from a dorsal.

Aspect to the ventral aspect. And we're going to move progressively forwards and then keep going until you've seen the very cranial and ventral extent of the spleen. The middle portion of the spleen is normally reported to be less than 15 centimetres in depth.

But I think what would be more useful than that measurement really would be a subjective assessment of how that looks compared with how the spleen usually looks in an animal of that size. This is an image of a splenic hematoma in a horse that's sustained an abdominal trauma. This is another image from the same horse, but I wanted to include it because I think it demonstrates quite well how variable those hematomas can look.

But also, this area, I think, looks very similar to some other abnormalities that we can see in the spleen, such as some of the neoplastic processes or an abscess. And if you were to see this, depending on the clinical history, you may well need to perform further diagnostic procedures to determine what it is. This is an image of a splenic abscess.

And this is an image of a lymphomatous mass in the spleen. Next, we're going to move on to the inguinal region. We're going to place the probe in a longitudinal direction.

And we need to get right up into that inguinal area. We're going to angle into the abdomen, and we're going to fan away from and towards the lateral wall. The organs seen will be the small intestine.

The colon, the bladder, if relevant, the uterus, and sometimes other organs. So normal small intestine can be difficult to see when it's collapsed. If you can't see it, that's usually a good thing.

It should be contractile. The wall should be visible, but not easily measurable. And the wall should be uniform.

I'll just mention at this point that wall thickness is reported to be 2 to 4 millimetres when it's normal. However, I definitely think you see cases where the measurements are within that range, but it is abnormal. So, I think the subjective assessment is likely to be more useful than the objective measurement.

And the other problem with the objective measurement is that it will be quite variable depending on how contracted the loop is. On the right of the image here, you can see normal small intestine contracting. So potential small intestinal abnormalities.

We may see thickened wall, and that can either be due to edematous infiltration or cellular infiltration. We may see focal disease of the wall, for example, a foreign body granuloma or a neoplasm, and we may see ventral sedimentation. So this doesn't actually affect the wall, but it can be mistaken for a lesion in the wall if you're not familiar with it.

I will demonstrate that shortly. So here we have thickened small intestine, and you can see that the wall of the small intestine is subjectively thickened, both when the loops are contracted and more distended. Here you can see the ventral sedimentation within these loops.

So decrease in motility in the small intestine can be caused by a number of things, and that can be any of the types of small intestinal obstruction that we see, whether that's physical or functional. When it's due to a physical obstruction, the level of distension can be variable, but can be marked distention, so severe circular, up to 5 centimetre loops of small intestine, with functional obstructions. This can also Cause significant distention, but particularly when this is following Buscopan administration or sedation, usually, this is mild, so we wouldn't see the big round circular loops, but we would just see more lumen than we would usually see and a reduced rates of contraction.

This is a video from a horse with a junal obstruction, and you can see both normal small intestine contracting in the centre of the image and abnormal, severely distended loops of small intestine. So the functional loops of small intestine are distal to the obstruction, and the distension is proximal to the obstruction. You can also see ventral sedimentation in one of the loops here too.

So now we'll move on to the bladder, and just a reminder that we're still talking about scanning in the inguinal region. So if the bladder is empty and the adult horse, it may not be visible. If it contains urine, this may either be anechoic in nature or mixed eogenicity.

Normal urine sediments can look bizarre. In this image, we have a cytolith causing acoustic shadowing, but we also have normal sediments present. And you can see that there's a mixed ecogenicity there.

The wall of the bladder, mixed with the ecogenicity of the sediment can be mistaken for an abscess or a mass. I think that's an important thing to be aware of. Next, we're going to scan the left ventral abdomen.

The probe is going to be somewhere between vertical and at the angle of the ribs. We're going to the scan again from dorsal to ventral over the highlighted area. Moving from the caudal aspect to the horse to the cranial.

Most of this area will be occupied by the left ventral colon. So what is normal? As it's a gas-filled viscous, even when not gas distended, we expect the outline to be hypoechoic and not to see into the viscous.

It will be circulated. And it will be slowly motile. The wall will not be easily discernible.

So, if we're scanning this area and we obtain this image, I would in fact increase the depth. So we've already scanned the spleen. Now we could increase our depth, move our focal point to be looking at the ventral colon, which is occupying the bottom part of this image.

We should also be looking for any other abnormalities that we might see in this area, and that could include abscesses or neoplastic masses. This is a large mesenteric abscess sitting between the colon and the spleen. So next we'll move on to the plural space.

So, in order to assess this assess this area, we'll need to decrease the depth on our focal point significantly to approximately 6 centimetres in depth. We may wish to change our probe. You can absolutely scan the plural space with this sector probe that we've already been using, or alternatively, you can switch to a linear high frequency probe, and you will get a higher resolution with that type of probe.

So that lung surface should be smooth. It should be hypoechoic because the lung is aerated and therefore filled with gas, so we should not be able to see deeper into the lung parenchyma. The red line here marks the surface of the lung.

And in this image, it's reasonably smooth. There should be no long consolidation, and in some cases, mainly with pneumonia cases, you can sometimes see into that parenchyma, and it can appear a similar structure to liver, and that, of course, is abnormal. There should be minimal pleural effusion.

Up to 3.5 centimetres can be within normal limits, and we need to measure it at its deepest point. Here you can see a degree of pleural fluid.

In this horse, this is within normal limits. And of course, we don't want to see any small intestine in the plural space. Diaphragmatic herniation is not common, but it does happen.

This is a video from a tachycardic horse. The plural surface of this lung is abnormal, and you can see small areas of consolidation which lead to comets tail artefacts. So these are the vertical hypoechoic lines emanating from the surface.

The lung usually lies against the thoracic wall, and in this case, you can see that it is slightly deviated from the wall. That is within normal limits in this case, because the amount of pleural fluid that we have is within the 3.5 centimetres.

So that can be a normal variation, or it can be abnormal depending on the degree of fluid accumulation. The structure on the right of this video is the pericardial diaphragmatic ligament, and that can sometimes be seen moving around in the plural space. Now we're going to move to the right side of the horse.

First, we're going to start with the right kidney and duodenum. Then they seek him. Then the inguinal region, then the liver and right dorsal colon, then the ventrum, then the right ventral abdomen and cranio ventral abdomen.

This will be mainly the right ventral colon. And the right plural space. So when we scan the right kidney, we're going to have the probe pointing slightly cranially and slightly ventrally.

Again, we're going to move from dorsal to ventral and it's only going to be over 2 to 3 intercostal spaces over the highlighted area. Like we did on the other side of the abdomen, we're going to use the technique of scanning and angling slightly cranially and slightly cordially to give us a comprehensive view of that area. So what's normal for the right kidney?

It should have a regular outline. There should be no discrete areas of differing ecogenicity. The a degree of corticomodullary distinction should be obvious.

This is demonstrated by the red line. The cortex should be approximately 1 centimetre in thickness. This is demonstrated by the yellow line.

There should be no areas causing acoustic shadowing. And there should be no dilated areas. This gives this same kidney that we saw in the previous image, but in the context of the tissues around it, rather than as a cropped image.

I'd just like to mention, while we're looking at this image, that a totally normal kidney can look really quite abnormal when viewed obliquely. So it's best to always try and get a Transection of the kidney right through the longitudinal plane perpendicular to the kidney. So, In this image, I think we have achieved that.

But it's remarkable how abnormal a kidney can look when viewed obliquely. So if you think a kidney looks quite abnormal, then I would just alter your angle and view it from different intercostal spaces and angles before making a final decision about that. So this is a kidney with Nephrolithiasis, causing acoustic shadowing and secondary focal renal pelvis dilation.

In this image, the kidney has an overall increase in ecogenicity, but particularly at the corticomodullary junction. This can be seen in a number of circumstances, but particularly with ischemic injury, often associated with non-steroidal anti anti-inflammatory administration during hypovolemia. This image could also be seen with acute pyelonephritis.

And you can see a kidney with a renal melanoma. Here you can see a renal cyst. So the duodenum is the only piece of small intestine that can be reliably visualised in particular places.

So it's attached both just cranial to the dorsocranial pole of the right kidney and also adjacent to the right dorsal colon. Next, we'll move on to this assessment of the secu. The probe is going to be held vertically, initially when we are caudal to the ribs, and then at the angle of the ribs as we move on to that area.

We're going to start at the caudal extent of the area highlighted, and we're going to move from dorsal to ventral and then we will repeat this process moving cranially. So what's normal for the equine secum? It's slowly motile with occasional large contractions.

You can't usually differentiate the wall. You don't usually see fluid within it? And you may see small non-distended vessels on the lateral aspect, in contrast to the colon colon where they should not be seen.

This is a horse with tiphlo colitis, and we can see into the lumen of the secum, which is fluid-filled, whereas usually we can just see that hypoechoic contour because of the gas. This is an image of a seeker sequel into susception. Next we'd move on to the inguinal region.

This is exactly the same as assessing the left inguinal region, so I won't go over it again. Next, we'll move on to the right dorsal colon and liver, which will be visualised through the same window. The probe will be almost vertical at the angle of the ribs.

Looking straight across and slightly cranially. We're going to move from dorsal to ventral again over the highlighted area. So here you can see the right dorsal colon demonstrated in green.

So what's normal? Again, it's gas filled, so it should be a hypoechoic structure. It's in a standard location unless displaced.

Smooth surface as non-succulated. And no fluid should be visible. It will be moving slowly.

And you shouldn't be able to easily differentiate the wall. This is an image from a horse with severe right dorsal colitis, and you can again see that that wall is hypoechoic to the colon. And this is a severe case with thickening of almost 4 centimetres of wall.

I wanted to mention the. Distension of colonic vasculature, which can be sometimes seen on the right side of the abdomen with large colon displacements or torsions of the large colon. So here you can see a vein and artery, which sit well, do sit on the medial aspect of the colon.

So they're not usually visible as they sit deep to the gas within the colon and therefore cannot be seen. But when this colon is in abnormal orientation, these can sit most laterally. And the ones in this image are also distended as well.

They should not be that size in the normal healthy animal. This is in contrast to the normal faecal vessels, which will be much smaller and shouldn't be distended. So to assess the liver, we're going to have the probe at the angle of the ribs again.

Doing our technique of scanning cranially and cordially from each position. And we only need to move a small amount from dorsal to ventral. So here we've got the liver.

So what's normal, it should not extend beyond the costochondral junctions on the right side. It should have sharp edges. It should be homogeneous in appearance.

And it should be hypoechoic compared with the spleen. You can see hepatic vessels, usually, but they are not prominent in the healthy animal. So this is a case with hepatitis, and you can see rounding of the borders of the liver, and you can also see areas of increased ecogenicity.

In this case, you can see marked vascular distention within the liver. Here you can see hepatoliths within a bile duct, causing both acoustic shadowing and. Billary tree dilation.

Next we move on to the ventrum. The way I tend to approach this is to start from the sternum and work in a cranial to caudal direction with a probe in a transverse orientation. Here we have the spleen on the left side of the abdomen marked in the darker blue.

So, I would move from cranial to caudal and then repeat this a number of times, moving laterally each time. So what's normal in an assessment of the ventrum? As the spleen should predominantly be on the left side.

It can be up to the midline and occasionally slightly over and still be within normal limits, but if it's considerably over there. The midline, then it's likely to be associated with an abnormality, whether the spleen directly or whether the spleen is being displaced, and that would most commonly be due to left dorsal displacement of the large colon. We also usually see colon in this image.

And potentially peritoneal fluid. A potentially small intestine. So what's normal when we're looking at peritoneal fluid?

There should be a small volume. Should be anechoic. There are many causes for an increase in volume.

Regardless of the course that most often will be anechoic. I think this is an important observation because even with bacterial peritonitis, which we might think would Give us the appearance of a more ecogenic fluid. I think probably due to the resolution of our images that we obtain when scanning equine abdomens, you can have a bacterial peritonitis with a significantly increased cell count and the fluid may still appear anechoic.

It may not do, but it may do. You may also occasionally see changes consistent with heme abdomen, such as swirling and mixed ecogenicity. And this is an image from a case with a heme abdomen.

Next, we'll move on to the right ventrolateral abdomen. Here we'll have the probe vertical to at the angle of the ribs. And again, we'll move from dorsal to ventral over the highlighted area, angling cordially and cranially as we go.

Thought's normal for the right ventral colon. Again, it will be hyperchoic as it's a gas-filled viscous. It will be sacculated slowly motile, and the wall should not easily be discernible.

After we've assessed this area, we'll assess the right plural space using the same principles as we did for the left plural space. So in conclusion, abdominal ultrasonography can provide valuable information in a variety of cases. Good patient preparation can really help you to get useful images.

A systematic approach will enable you to gain useful information and not to overlook pathology. And also, you may have now realised that it's an interesting and enjoyable technique to use. Thank you for listening.

I really hope you found this presentation useful. I'd also like to thank the people listed below for contributing images to this presentation. Please feel free to contact me if you have any questions.