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November 2, 2023 — Dr. Kelly Diehl talks with equine health expert Dr. Sharanne Raidal about colic in horses. The pair talk about diagnosis, causes and treatment. Dr. Raidal also covers her latest research on the risks of transportation on colic. 


Colic – an emergency for horse owners and a top research focus for the Foundation 
60+ years of helping horses live longer, healthier lives 

0:00:11.0 Dr. Kelly Diehl: Welcome to Fresh Scoop, Episode 62, Understanding Colic in Horses. I'm your host, Dr. Kelly Diehl, Morris Animal Foundation, Senior Director of Science Communications. And today, we'll be talking with Dr. Sharanne Raidal. Dr. Raidal is Professor of Equine Medicine at Charles Sturt University in Wagga Wagga, Australia. Welcome, Sharanne. 

0:00:36.5 Dr. Sharanne Raidal: Hello, Kelly. Thank you for talking to me. 

0:00:39.6 DD: Oh, yeah. Hopefully, I got your name correct. [chuckle] I will practice. 

0:00:44.4 DR: 100%. 

0:00:44.8 DD: Great. Before we get started, I always ask people to tell us a little bit about yourself and what led you to become a veterinarian and then specialize in Equine Medicine.  

0:00:56.7 DR: Oh, this might be the least interesting part of the talk, Kelly. A pretty cliched response, really. I grew up in Sydney, so I was a city kid, but I was medically inclined and thought that perhaps, like medicine... Oh, excuse me. Sorry, that's not COVID-related. 


0:01:14.6 DR: So just wanting to exercise that sort of medical inclination, I guess, but I liked the idea of working outdoors and particularly the idea of working with animals. So I started vet school, but took a year off after third year thinking that as a city kid, I should learn hands-on how to work with large animals. So I was planning to have a year as a Jillaroo, as we call them in Australia, but maybe a farmhand in the northern hemisphere. But a job came up on a thoroughbred breeding farm, which I took and loved. So I went back to vet school thinking that I could focus on just one species and not have to perhaps have expertise across every species. 

0:01:58.7 DD: That's a great story. As another city kid who ended up having a work-study job as an undergraduate on a sheep farm, it was a really great experience. I'm glad to hear of another city kid who did well with, in large animal. As we get started, I think there may be some confusion around the term colic. Many people hear it, and we often think of infants, but what is the definition of colic as it relates to horses as you apply it?  

0:02:36.3 DR: So I think it borrows from the terminology in babies. So typically, when we use that word, and it's some stricter sense perhaps, we're assuming that the horse's abdominal pain or, more specifically than that even, pain attributed to the gastrointestinal tract. But in reality, like babies, horses can't speak to us. So we do just have to keep in mind that the pain could be due to any other organ in the abdominal cavity and sometimes even to other conditions. So, so sorry about that. 

0:03:08.3 DD: No worries. 

0:03:09.2 DR: So sometimes even other conditions such as tying up or pleuropneumonia and even laminitis will sometimes present in such a way that they can confuse or be suggestive of colic. And then sometimes owners will even use the word colic for want of a better word when the horse just ain't doing right. So, it can be very broad. For vets, when we're talking to owners, it's really important when that term comes up that we just keep an open mind about just how expansive the clinical presentation could be that's captured underneath that umbrella term. Strictly when vets, or when I use the term colic, the assumption, and sometimes it is only an assumption, is that we've got pain that's attributable to the gastrointestinal tract. And then there are a number of discrete presentations that we can recognize. I think it's also important to remember that if we're looking at colic as due to gastrointestinal pain, then we need to sort of think about what are the mechanisms of pain, like what bits can actually be hurting here. And in broad terms, we can have distention of the gastrointestinal tract, so it could be distended with gas or fluid, and that's a little bit uncomfortable. We could have tension on a support structure, so the mesentery or the ligaments essentially that hold the gut in place. 

0:04:33.5 DR: It could be due to inflammation, or it could be due to Ischemia, which is just when there's an inadequate blood supply to the bowel, and that would probably be the most serious presentation. So within those sort of four broad mechanisms, we then have to think about, well, what's actually gone wrong to cause those things? So, typically, we think about obstructive lesions, so that could be something within the gut that's just blocking passage of ingesta, and an impaction would be the most sort of common and maybe benign presentation there. But we could have an obstruction that's due to something on the outside of the bowel compressing the lumen, and that could be because some of the intestine has displaced or traveled to a place in the abdominal cavity where it doesn't belong. And if that's just a simple displacement, then sometimes that bit of bowel will march right back to where it belongs, and the colic will go away. But sometimes, unfortunately, there's a bit of a design flaw in the horse in that they've got a number of parts of their gastrointestinal tract that aren't particularly well tied down. And those parts of the tract can displace into unusual or inappropriate conditions. And if they twist on themselves when they displace, then they can actually strangulate themselves, so then you get strangulating lesions. 

0:06:09.2 DR: And then one final thing that I was thinking we certainly need to always remember down here in Australia, and I think it's the same worldwide, is that occasionally, when we have a horse presenting with acute diarrhea, the initial sign may be colitis. So that would be pain due to inflammation of the colon, very similar to when we have, well, I assume it's very similar to when we have diarrheic pain. So sometimes, the first clinical sign that the owner will see with diarrhea is a horse that can have really quite severe colic. So we again just need to keep in mind that even severe colic is not necessarily surgical colic. We need to just work out what the underlying problem is. 

0:06:53.7 DD: And I don't know if you know this. I've seen some statistics bandied about, but can you give us a sense of, for example, how many horses are diagnosed with colic each year or what the chance is that a horse will have an episode of colic in their lifetime and then maybe follow up with some mortality data?  

0:07:15.2 DR: Yeah, that's actually a surprisingly difficult question. I think because the definition and the term is so broad, and because we need to think about whether we've got a veterinary opinion of colic versus owner observation of colic that may have resolved by the time that the vet gets there. And then, even with a veterinary diagnosis of colic or do we have just a field observation that the horse is in pain, or do we have a specific type of colic? So when we look at the literature, we've got to sift through all those various considerations, and there are surprisingly few studies that have actually done that. But I guess the best information that I could access in that sense was some overall data. And the sort of most reliable numbers that I can access are that overall, we've got something like between one and 10 horses with colic per 100 horse years. So what that means is that if we're looking at 100 horses for a year, we could expect that between one and 10 of those horses would have colic within that year. So I guess across a horse's lifetime, that depending on how long you expect your horse to live for, that's going to equate to probably one in every three to five horses would have at least one bout of colic during their lifetime. 

0:08:45.7 DD: So, in other words... 

0:08:47.1 DR: I think it's... 

0:08:47.2 DD: Oh, it's pretty common, right?  

0:08:48.9 DR: It is pretty common. And certainly, when you look at causes of mortality and causes for veterinary presentations, it's probably the single most common medical presentation. I think certainly in Australia, lacerations, so cutting their legs and hurting themselves generally in the paddock, seem to also be ways that horses find to cost owners money, but certainly very common. And I think the other thing with those numbers is that like you or I might experience transient abdominal pain that self-resolves and that we'd never need to talk to a doctor about. Probably every horse is going to have that kind of discomfort. 

0:09:29.3 DD: Right. And you touched on this a little bit, but can you talk a little bit about the different types? You talked about lesions, problems from within and from without the gastrointestinal tract, but are there specific terms? I've heard some like sand colic, right? And... 

0:09:48.0 DR: Yeah. 

0:09:48.1 DD: I'm sure you've heard more. Can you review some of those for us?  

0:09:52.8 DR: Sure. I guess things like sand colic tend to be very geographic. So we've certainly got locations in Australia, and I know in the States, Florida, particularly prone to sand accumulation, and that's going to be because of the local soil conditions. So it's maybe sort of less helpful or less specific, I guess, to talk more generically about what goes on. And basically, I sort of tell our students, we've got two types of colic. We've got the mild self-limiting kind, which will tend to go away almost despite our treatment. And sometimes on a call-out, you go out and you wonder whether or not you actually did anything for the horse. And then you've got the more severe kind. And I know our students are often quite worried about their ability to differentiate these on graduation, but they are very obvious when you sort of see the two extremes. And I guess the distinction here is really important because you asked me previously about mortality. And this straightaway talks to that because we know, for specific conditions, what our predicted mortality rates would be. And sometimes, we can give an owner a more accurate estimation of mortality for each individual horse, not until we actually get them on the surgical table and can have a look at how much damage is going on inside the abdomen. 

0:11:26.8 DR: But in general terms, those mild self-limiting colics, you're looking at 100% resolution, at least on first presentation. The problem with that is that the horse that colics once is more likely to colic again. So certainly, that's a little bit of a concern because there are a number of studies that have shown, if we go back to the 100 horse years concept, horses that have had a prior bout of colic are more likely to have colic again. So you sort of go up to 30 or 40 cases of colic per 100 horse years in horses that have had a prior episode of colic, even if it's mild. So certainly, they would be horses to watch and whether that's because there are management factors that are contributing to their colic or whether there are just individuals with marginal differences in their physiology that lead them to be prone to recurrent colic is not determined. So, going back then to thinking about our second type of colic, which is the scary colic for all of us. And these are colics that are more serious, and they are written all over the horse large and they mostly relate to the intensity of pain. 

0:12:44.4 DR: So how severe is the horse's pain and then whether or not we've got clinical signs of shock or toxemia, to use lay terms. So basically, what I'm saying there is that we need to look very carefully for whether there's any evidence of other organ dysfunction and particularly cardiovascular changes as a contributor to both understanding the severity of our colic presentation and therefore how much treatment we need to render and also what the prognosis is. 

0:13:18.9 DD: Yeah, thanks for... 

0:13:20.4 DR: So... 

0:13:21.1 DD: Ooh, sorry, go... Keep going. 

0:13:21.3 DR: Yeah, I know, so... No, I was just going to say these horses with serious presentations, so severe pain and clinical signs of shock and endotoxemia without intensive care, those horses will almost certainly die. And sometimes, this is treatment and care beyond what you can offer the horse in a field setting. 

0:13:41.1 DD: Right. And I appreciate you looping back around. I realized I didn't hear the mortality data, but I think that it is hard. We at the Foundation sometimes struggle when people ask us about statistics on colic because, for just the reasons you've mentioned, I think we have better data when horses end up at the veterinary teaching hospital, but that is a skewed population, right? Those are only... 

0:14:08.9 DR: Yeah, absolutely. 

0:14:10.5 DD: The most serious cases. Looping back, you talked about pain and the diagnosis of colic, but for people listening, I think you've put your finger on something that I hear from owners and practitioners. And I certainly was worried when I was first out in practice many, many, many years ago about recognizing colic. So, review for everyone a few of the most common signs that are reported. 

0:14:38.8 DR: So again, there's a big spectrum here, and they range from the horse, as I said, that just ADR ain't doing right, to the horse that it's so painful that it can't stand. So it's on the ground and it's rolling to the point that it's hurting itself and that it's a risk to its owner or to handlers. Or we might see evidence of skin abrasions or disturbed bedding or other things that tell us that the horse had had a severe bout of colic, but that seems to be resolved at the moment. So we need to look carefully for that in real time or, as I said, as an observation based on the horse or its environment. If we're looking at more subtle signs, it might be just the horse that's flanking, that's just looking around to its side from time to time, or it might be purring. Quite commonly, with low-grade colics, we'll get a horse that's stretching out frequently to urinate and particularly with male horses, this might make an owner concerned that the horse has a urinary tract problem. And urinary tract problems, while they occur in horses, common things occur commonly, right? And colic is much more common than a urinary tract problem. So we just need to sort of keep that in mind. 

0:15:51.5 DR: Sometimes they'll do strange things, and you mentioned sand accumulation. My observation, and it's purely anecdotal, is that horses with sand will often dog sit or roll onto their back and just lie on their back with their legs in the air. Sometimes we'll see abdominal distension or other changes that sort of clue us in. We may have a horse that's inappetent. We may talk to the owner or look for evidence around the passage of feces, and this is variable. It can be normal because if a horse has got a lesion or a problem that's at the front end of the gastrointestinal tract, then there's quite a lot of feces at the back end still to come out. And so sometimes we don't necessarily have a change in the passage of feces, but it's pretty common. We'd expect to see that there could be a decreased or no passage of feces associated with a problem, or we might see that there's an altered consistency. So, commonly this might be that the feces are really dry and bally. 

0:16:58.6 DR: Sometimes the horse that's having decreased gastrointestinal passage of ingesta will pass feces that have... They look like they've got a skin on them, and we call that a pseudomembrane and that's just dried out inspissated mucus, and owners are often concerned about that. They sort of see it and think that it's, like I said, a skin or worms or something that they don't recognize, and that's just a red flag that we've got decreased fecal passage. And then the other change I mentioned, diarrhea. So we need to sometimes be considering or looking for diarrheic feces. We get sort of non-specific signs, again, like bruxism or teeth grinding, which has been linked specifically to gastric ulceration but is probably more generic rather than specific. So it's just general low-grade pain or a flehmen response where the horse sort of stretches its neck out and curls its top lip out. That's again just an indication that the horse is telling you that things aren't quite right. 

0:18:06.6 DD: And that brings me to something I wanted you to walk us through, which is, and I'm going to paint the scenario for you, maybe of a horse that's referred in for potential colic. How do you approach that patient? What steps might you take as you examine that particular individual?  

0:18:28.9 DR: Yeah. So the veterinary workup, I guess, begins as soon as you make the phone call, whether that's to an ambulatory vet coming out to your place or whether it's a horse that's coming in to see us. So it may start with a signalment. So if you've got a mare that's recently postpartum, then that opens up a few considerations that we wouldn't think about in a stallion, for example. If you've got an old horse, then we're going to be worried about a strangulating lipoma. If you've got a young horse, we're going to worry about intestinal parasites, although we probably worry about those in every horse, just different species of worms. So signalment can be important more to type of colic rather than prognosis or risk of colic. So that would be the first thing. And then we're going to talk to you about the horse's history. And we know that any kind of management change is a risk factor for colic so... And some types of diet. So we'll talk to you about the horse's diet or changes to its diet. We'll talk about management changes to stabling or accommodation. And again, you mentioned sand colic as a specific instance of colic. 

0:19:36.7 DR: We might look at whether or not your farm is located in an area where there's a farm. Or the other thing is that we have a number of horses in Australia that are kept on sand now because we're looking after their laminitis. So even in an area where sand colic is not endemic, we might for management reasons have a horse that is able to accumulate sand. We're going to look at the level of exercise and whether or not that's increased or decreased recently. We're going to think about transportation. Hospitalization is a risk factor for colic. We always worry about our patients because we've imposed on them. Pretty obvious and substantive management changes. We'll look at the horse's anthelmintic history and especially relevant to management. So I think we're realizing now that there's no one-size-fits-all approach to parasite control in horses and we've certainly got concerns about anthelmintic resistance. So we need to consider that. And in Australia, because of Hendra virus, we need to look at the horse's vaccination status. I'm not aware of any infectious causes of colic in the Northern Hemisphere other than to say that certainly the risk of diarrhea would be a consideration with a horse coming into, to hospital. 

0:21:02.9 DR: And then when we actually see the horse, and sometimes this is all happening while we're talking to you, we can observe the severity of colic and that's going to truncate the amount of time we'll spend talking if the horse is actively colicking and severely discomforted. But we might talk to you about how severe is the colic that you've seen and the clinical signs that you're able to see and recognize. But then, when we actually start to look at the horse, we're going to focus on just a thorough and complete physical exam. And I certainly like to prioritize getting an accurate heart rate from a horse and this needs to be a resting heart rate. And the reason that's important is that we've tried very hard over the years to give owners information that relates to prognosis so that we can accurately stage the severity of the horse's condition. And heart rate comes out again and again as being important. And depending on the study, a heart rate above 60 or a heart rate above 80, so somewhere in that range of 60 to 80 for an adult full-size horse, is where I start to sort of get concerned. And if I've got a heart rate that's that high, I flag that straight away as a horse that's in the serious severe colic category rather than a mild colic. 

0:22:34.4 DR: We're going to look then also at other aspects of its cardiovascular system. So, its capillary refill time and mucous membrane color. So, just opening up the horse's lip and looking at its mucous membranes. And usually, the reason that I get a heart rate initially is that most horses get a little bit ticked off when we start trying to open their mouth. And I don't want their heart rate to be artificially high because I've weirded him out by looking at his mouth. I want the horse also to have time to settle after it's got off the float, too. So, just coming back to that heart rate being a physiologic heart rate or a heart rate that's due to the condition, not due to anything that I'm doing to it. So we're going to look at our mucous membranes. We'll look at the jugular refill. So, is there a nice brisk refill to the jugular vein? Looking at the digital pulses is going to be important because there is an association between colic and laminitis in some instances. So we're concerned about whether our digital pulses are bounding or increased. But more commonly, in my hand certainly, they're going to be decreased if we have a horse that's exhibiting signs of shock. Might just may be that it's a bit cold, and their peripheral circulation is not as good as it... It doesn't need to be as good as it normally is, but certainly we'll pay attention to those digital pulses and also the vascular tone. 

0:24:05.1 DR: So it's one thing to have a digital pulse that is hard to palpate. But I want to know what the vessel tone is like because horses that are shocky are going to have flabby vessels. So, I can't really palpate their arteries, which is concerning. And then I also want to feel the extremities, whether they're cold because they're not being perfused. And so feeling the heat, sorry, the feet, the nose and the ears, just to know whether or not that's sort of giving me a picture of a horse that really doesn't have adequate perfusion of its extremities. We'll usually listen to the lungs, so pulmonary auscultation. But to be quite honest, if I'm convinced that we've got a colic horse, and particularly a horse that's discomforted, I'm not going to spend a lot of time on this unless I can see evidence of respiratory dysfunction. We'll focus on our gastrointestinal auscultation. So we're going to listen for gut sounds and typically we listen in all four quadrants. But at least you want to listen to both sides of the horse's abdomen. And circling back to your point on sand colic, we want to auscultate ventrally, so underneath the horse's abdomen, just behind its ribcage. 

0:25:19.7 DR: For sometimes we can hear sand. If the gut is really still, then the sand is not moving and we can't auscultate it. It's not a particularly sensitive test, but I do like to listen for that. I like to listen for gassy or fluid sounds, if there's motility at all, and percussing the abdomen. So just, I usually just use my fingers to percuss, listening for areas of tympany or gas accumulation within the gastrointestinal tract. Usually, at this point, or possibly even sooner, I will have collected a blood sample and I usually do that as soon as a horse walks in. I usually take bloods that I can send to the laboratory. But to be perfectly honest, with acute colics, laboratory bloods seldom come back to me in a time that is meaningful in real-time. It's often useful if we're recovering a horse from colic surgery or something along those lines as baseline value. But normally we rely on what we call point-of-care testing. So they're really simple things like PCV and total protein that tell us how dehydrated or how concentrated the horse's blood is, whether or not they're losing protein from their blood vascular space. We look at an analyte called lactate as again, a really good prognostic indicator. 

0:26:44.3 DR: And this is something that we can measure in the field. There are very portable lactate machines that will give quite accurate measures of blood lactate concentration. And then depending on the horse, we may measure triglycerides as an acute consideration. I'm spoiled because I work in a hospital setting. I usually get venous blood gas results at this time and what I'm interested in or what I get from the, our blood gas machine, is the measure of glucose, which is usually not relevant particularly to adult horses. They usually have slightly high glucose because they're stressed, but I want to look at their electrolytes and acid-base status and so I can get that. So I try to do all of that or at least get the samples so that somebody else can be running that for me before I start messing around with the horse, because as with a heart rate, anything that I do clinically has the potential to artificially elevate some of the analytes. And then, particularly if I'm going to sedate or give the horse any analgesia, the drugs that I give it might affect those numbers that I'm looking at to give us prognostic information. So that breaks down to immediately or very quickly after the horse arrives, I'll get an accurate heart rate and I will get bloods with those point-of-care analytes being the information that's most important to me, and I'll listen to the horse's abdomen. 

0:28:21.2 DR: Depending on how the horse is going and whether or not we're getting a sense that it's a serious colic or a classic colic presentation, we'll move through a range of ancillary diagnostic procedures. And where, again, I've been spoilt because I've had access to abdominal ultrasound for quite some time. But one of the developments that I think is really exciting in this space is that there are a number of point-of-care probes that were developed for use in the human intensive care setting and these probes connect wirelessly or by a cord to smartphones or tablets and give us quite immediate access to diagnostic quality ultrasound. And surprisingly, because human, you know, probes that were developed for human use often don't translate well to application in horses because of the size of our patients. We're actually finding that most of these probes are working really well for us in the field and that we get from these more readily available point-of-care probes. We get probably 70% or 80% of the information that we can get from a much bigger, more expensive and less available ultrasound machine. 

0:29:43.7 DR: So I think these probes and the ability to do a field evaluation of the horse's abdomen by ultrasound is much more available now. And that helps us to not identify all things because even with the best ultrasound setup I can probably only ultrasound 20 cm or 30 cm of depth around the horse's abdomen. So you can imagine the size of a big horse that doesn't give me the ability to visualize all the way through the abdomen and ultrasound can't go through air. So if I've got gas pockets there, my ultrasound can't penetrate the gas pockets. So, the technique has limitations but certainly it can help us evaluate the horse's abdomen, and particularly, I'm looking for gastric distention or small intestinal distention. And then there are a few other clinical signs that will illustrate ultrasonographic findings that will help me identify more specific lesions. We may want to do a rectal exam, and a rectal exam is a very useful thing to do, again, like ultrasound, because of the size of our patient, we can't explore the entire abdominal cavity. We can typically expect to only palpate the back quarter or a third of the horse's abdominal cavity, but still that gives us some useful information. Then if we're concerned that we've got devitalized bowels, so a bowel where the blood supply has been compromised, or if we're concerned that we have an infection within the abdomen. 

0:31:30.6 DR: So peritonitis or something like that or if we're concerned that the horse has already ruptured, we might do an abdominocentesis. And this is where we put a blunt instrument like a teat cannula or sometimes a needle into the abdominal cavity. And we're trying to get the abdominal fluid that bathes the intestines so that we can get information about the disease process that's going on within the animal. One other thing that I forgot to mention is that quite early on, particularly for a horse that's in severe pain, I will pass a nasogastric tube. And what I'm looking for there is reflux because some horses typically are not able to vomit. They are at risk for rupturing their stomach if we don't evacuate fluid that's distending their stomach. So I will check for that. My order of doing that has actually changed. With the availability of our ultrasound probes, I think we can quite quickly and accurately assess whether we've got gastric distension. So, I will look with ultrasound typically before I pass the stomach tube. And the reason for doing that it is that if I'm, depending on what our findings are and what the owner's preferences are, I may pass the tube looking for reflux or I may pass the tube looking to give the horse enteral fluids. So, looking to put some fluid in and see how the horse goes with those enteric fluids. 

0:33:05.6 DR: And then, I think there are some other tests that may be indicated, so again, circling back to sand, if we had a concern about sand colic, abdominal radiographs would be a really excellent idea to roll that in or out. 

0:33:22.0 DD: So that's a pretty, that's an excellent description, and to kind of talk about how you approach these guys. So why don't we keep going and tell us now you've done your exam, you've hopefully got some data from ultrasound, which is amazing. I'm actually surprised, having been an ultrasound, done ultrasonography as part of my internal medicine practice, that you have such great luck with the probes in such a large animal. Where do you go now with treatment after you do this?  

0:33:57.3 DR: So I touched on analgesia administration, that will certainly be both a treatment and a diagnostic tool. And that actually is one of the important questions even further back from the owner's history because we need to know whether owners have treated the horse with any analgesic medication and what response they got. So whether it was owner administered or whether it's by a referring vet or by us early in the course of investigation. We need to know what analgesia the horse has had and, importantly, how has it responded. And I talked about heart rate and severity of pain and lactate as being very important prognostic determinants. The response to analgesia is a very important consideration. And most commonly, we think about horses that break through their analgesic treatment as surgical candidates until proven otherwise. So analgesia, or response to analgesia, is a really important consideration for both treatment and diagnostic and prognostic information. Next, typically, we'll look at what we need to do by way of fluid therapy. And we've kind of got two considerations here. If we have a horse that's got gastric distension and/or cardiovascular compromise, then we need to put the horse usually onto a drip. 

0:35:30.2 DR: So we need to put an intravenous catheter or two into the horse and we need to look at fluid therapy, and that can be just resupplying maintenance fluids or replacement fluids if we think the horse is dehydrated, or we can talk about resuscitative fluid therapy if we think that the horse is shocky. So we would have a conversation there about whether or not that was necessary. If we think that the horse has an impaction colic and particularly here, the classic presentation would be that we've done a rectal exam and we can feel that there's a nice big pelvic flexure impaction. There's been some work done and we've got a good evidence base now to suggest that administering enteral fluids, so putting fluids into the horse's gastrointestinal tract directly, is the best way to address those intraluminal obstructive or impaction colics. And that's great news for the owner because tap water is so much cheaper than intravenous fluids. And we'll typically, if we've got the horse in hospital, we'll typically put an indwelling nasogastric tube in and we use quite narrow nasogastric tubes that are the size of your little finger usually, so they're well tolerated by most horses. And we can just put enteral fluids in as a continuous infusion. And it usually takes a day or two for those impactions to break up. 

0:36:56.4 DR: So the choice of whether we put fluids intravenously or into the horse's intestine is really important and does depend on what we're seeing as the presenting clinical signs for the horse. Typically, we're going to withhold food for the horse's colicky and particularly, I'm conscious that owners or referring vets need to be mindful of this because horses don't have a great self-preservation gene. And so sometimes when they've been a bit colicky and that stops them eating and we treat them successfully with appropriate analgesia, they'll think, terrific, I can go back to my food. And they may start eating again even though we've taken away the clinical sign of the colic but not necessarily address the underlying problem. So I'm usually a little bit cautious about feeding horses that have colicked and usually we'll talk to owners about re-feeding cautiously after I expect the analgesia to have worn off. So I'm not masking any clinical signs, and in such a way as they can observe the horse to make sure that it doesn't re-colic when feeding is recommenced. The horse that has definitive signs of a surgical lesion, so on rectal or on ultrasound, there are a number of clinical signs that predict strongly for the possibility or probability of a surgical lesion, or if we've got certain findings on our abdominocentesis, we've got a horse that's really likely to be a surgical candidate. 

0:38:40.9 DR: So, that decision needs to be canvassed relatively early because the best time to take a horse to abdominal surgery is as soon as we can before it's had time to become systemically compromised. So typically, we'll talk to our owners with a severe colic about whether or not surgery is something that they would like to consider for their horse, particularly thinking about the welfare of the animal, the prognosis associated with the condition, to the extent that we're able to predict that, and the financial implications of that decision. So that's a conversation, and that we usually start early for those reasons. And then the final thing would be or the final consideration that's often considered in field settings in particular, is whether or not we give antimicrobials. And I think generally, as vets and within the medical profession, we're becoming increasingly aware of the importance of antimicrobial stewardships. So we really need to be very wise about how we use antimicrobials because we're concerned that we're seeing increased resistance to antimicrobials. So, from that perspective, we don't want to use antimicrobials unless they're clinically indicated. In horses, in particular, they're very prone to antimicrobial-associated diarrhea. 

0:40:10.9 DR: So we've got an extra reason in horses not to give them antibiotics just because we can't think of anything better to do. So, really I'm only going to give antimicrobials to a horse that I am pretty convinced or totally convinced has peritonitis or some other localized infection that's likely to be responsive to the antimicrobials that I am choosing for it. 

0:40:38.0 DD: Yeah, it's a pretty involved procedure. And just comment quickly for folks who are listening, if they're old like me and I'm going to date myself, the prognosis, I remember probably we're talking 30 years ago, if a horse went to surgery, it wasn't great, but that's really changed, right? It seems like we've made some pretty big advances in getting horses successfully through colic surgery. And I wondered if you could address that a little bit for people who are listening. 

0:41:12.3 DR: Yeah. Look, if we take a sand colic or an impaction colic to surgery because it's not responding to medical management unless we find evidence of gut damage at surgery, I would expect an 80% or a 90% prognosis for those horses. So what I mean by that term or by that estimation is that they're 90% or better likely to leave the hospital and 80% or 90% chance of them having a return to full use and little or no ongoing problems associated with their colic. That said, horses are not designed to be tipped from their back and to have their abdominal cavity opened. There are always risks with abdominal surgery. So, particularly in some horse populations or some settings, post-op diarrhea can be a real concern. Incisional infections, there are a lot of things that can go wrong, but they tend to be less common in those sort of simple, large bowel lesions that we get on the table. Small intestinal lesions, I think we still need to be a little bit careful about. They have a poorer prognosis, a rougher recovery and a more expensive deal at the end of the day. So certainly, if I can tell from my pre-workup or pre-surgical workup that the horse has a small intestinal lesion, I'll give the owners a more guarded prognosis. And I think depending on what we find at surgery 50% to 70% is probably a more realistic estimate of prognosis there. And the owners would need to expect that the horse is going to have a more protracted recovery. 

0:43:01.5 DD: Okay. That's really, really helpful and so much better for the oldsters who may be out there listening. It's just light years from when I was in vet school 35 years ago, and even when I was a resident and watching some of these patients, even though I was in small animal. I get this question a lot, and so I'm going to put it to you because I have got to think you get this question from your clients as well, which is how they can prevent this from happening. Maybe in the same horse, or I'm sure if I get this from people who've been through, for example, a cancer diagnosis or a dog that's had immune-mediated anemia or some serious problem, and they want to know, how can I prevent this from happening again? What are some of the guidelines that you give your clients when you hear this?  

0:43:56.4 DR: Yeah, look, I think, I mean, the first thing for certainly the clients that I've been dealing with literally is that it's not your fault in most cases. And again, I think it's perhaps a bias population in that we tend to get horses that are referred in with committed owners, and they've been doing their best all over the horse's life to make sure that this doesn't happen. So I think the first thing is that we do just have to remember that there are some, like I said, design flaws in the horse. And so they are predisposed to a number of displacements because things aren't tied down as well as they might be. And also, just because they're hindgut fermenters, they've got a large colon full of bacteria, those bacteria will liberate large amounts of toxins, particularly endotoxin. And we've got an animal that's 10 times more sensitive to endotoxin than you or I or a dog, for example. So we do have some considerations there, and we've also got a large animal, so we've got some diagnostic limitations. So all of that means that we will have to live with colic. And I think what we can do reasonably to prevent or minimize the risk of colic would be to introduce management changes gradually. 

0:45:18.9 DR: And certainly whenever we do anything different, whether that's traveling someplace else to compete or whether it's a horse in hospital, with those management changes, we need to be particularly vigilant about what's happening to the horse and just monitoring their gastrointestinal function. We can focus on high-quality feeds because certainly large amounts of grain, or round bales and poor quality at the other end of the spectrum. Those kind of excesses if you like, or sometimes pasture access issues or geo sediment like the sand issue, just being aware of those risk factors for horses. We need to be aware of anthelmintic treatment strategies relevant to our management situation for each horse. So, in areas where tapeworm is a consideration, then we need to be aware of, or conscious of treating for tapes. But more commonly with gnathostomes and strongyles, we just need to be aware of intelligent use of effective anthelmintic treatments. And then the other factor, I guess, is just to be monitoring our horses. 

0:46:43.6 DR: So, really being aware of what their routine dietary intake is and noticing if they're off feed and noticing what their fecal output is, because they'll often be subtle clinical signs of an impending problem. I guess the other factor would be access to high-quality drinking water. So again, when we travel or when we take a horse away to compete, just being mindful that we need to monitor water intake - some horses are easy travelers and will drink readily from any water source. But some horses are perhaps a little bit more fussy. So, just making sure that we're confident that the horse has actually been drinking at all times. 

0:47:31.6 DD: Oh, you've given me a beautiful lead-in. So thank you [chuckle] for your Foundation-funded study. So tell us a little bit about it, like what question you're trying to answer, a little bit about the method you're using and where you're at, if you can share that. 

0:47:50.2 DR: So our research question, I guess, is that, building on the observation that transportation has been commonly associated with colic or with diarrhea in horses. I guess our hypothesis was that the reason for these observations is that transportation may cause changes to gastrointestinal motility. And the way that we've been looking at this is just using the Wi-Fi ultrasound transducers that are available now. And we've got, or we've defined for windows in the horse's abdomen to look at some small intestinal and large intestinal motility before and after the horses are transported. And the trips that they've been doing have been trips of 10 to 12 hours duration. They are horses being traveled with a commercial provider, so they're client-owned horses. And, we were apprehensive, I guess, at the beginning of the study, that many horses would not tolerate the ultrasound evaluation, that they would find the ultrasound transducer pressure was a little bit unfamiliar, or that the alcohol spray that we need to put onto the horses to get good contact with the ultrasound, would be unacceptable to them. Particularly because one of our windows for the small intestine is actually putting the probe up into their inguinal area. 

0:49:24.3 DR: I have to say we've done 30 horses now, and I think that was eight trips. And we've had horses remarkably tolerant of us ultrasounding them to the point that I can actually ultrasound them often with them not held or tethered at all. And we are getting excellent images. And I have qualitative opinions, but we have been storing our ultrasound images as 62nd de-identified video clips so that we can make sure that we're using blinded evaluation to identify any changes that we're seeing. We're looking also at these horses, of course, for any physical examination changes associated with transportation. And we're seeing what's already been widely reported that the horses tend to come off the truck with high heart rates, sometimes elevated temperatures, but they recover rapidly. One thing that surprised me, I guess, is that looking at these horses, we're seeing that they may not urinate for the two or three hours that we're observing them off the truck, and they often don't defecate in that time. And the defecations on the truck have been surprisingly small. And so that does suggest to me that looking at those common things, you don't need an ultrasound or a vet to tell you that the horse has defecated less than you might expect. So even though we, our study is not designed to capture that information in real-time or with any degree of objectivity, I guess, certainly as an area for future study, I think really astute observation in that space is likely to be helpful. 

0:51:18.7 DD: Okay. And that was another, actually going to be my next question, so well done. You're a great co-pilot on the podcast adventure because you set, you tee me up very nicely for a question I wanted to ask you, which is, what are some of the big questions that you, as a clinician, your colleagues feel we just don't know about colic that you would just love to know, some of those big black box kind of problems. 

0:51:48.9 DR: The big ones for me are those philosophical questions like, why are they made the way they're made, and why are they so sensitive to endotoxin? More and more beautifully though, what can we do about this, I guess are the big questions. And I think looking at whether or not early indices of GI dysfunction are going to be helpful to us in picking horses that are at risk to GI disturbances. And I think it's early days, and it's going to be sort of speculative because the incidence of colic after transportation is probably not that great. And one of our commercial partners gave us some incidence figures that really speak to how uncommon the problem can be in well-managed horses. So we don't sort of want to come up with an idea that's expensive to owners or that's invasive and uncomfortable for the horse when it's not necessary. But doing common sense things like looking at fecal output, again, outside the scope of this study, but collecting urine samples and looking at how concentrated the urine is would be a really useful way of monitoring how dehydrated a horse is in transit. And certainly, some of the ultrasound findings that we're getting. We've not... The 30 horses that we've looked at to date, we've not had any problems in those horses they've recovered just fine on their own. 

0:53:24.8 DR: But there are certainly some changes where as a veterinarian I'd be thinking, gee, if this were a horse that I was responsible for, I would maybe err on the side of giving this horse an electrolyte drench or just certainly keeping it under special observation because of the changes that I'm seeing with ultrasound. So whether or not those findings are generalizable to a bigger population, I guess, becomes a question for future research. And then I guess the other thing is for owners, I would love to have information on what is effective prognostic information because it's very, it can be very expensive to take owners through a horse with colic. And the more accurate that our prognosis can be, the better. And just trying to take numbers that are derived from an entire hospital population and applying that to each individual horse, I guess, the more information that we've got in that space, the more effective we can be. 

0:54:41.2 DD: Well, I think your study is going to have a lot of practical applications. And it sounds like, again, you're getting some great information, so I'm optimistic and excited to see what you find. I'm going to go to the other end of the spectrum a little bit. We talked about the biggest questions looming out there for colic that you would like to know the answers to. But what are some of the biggest misperceptions you hear, both from veterinarians that you meet or you interact with out in the field and from owners?  

0:55:17.5 DR: I guess certainly, and understanding that not all colics are the same would be really important. So to me, I think with owners just having some idea of what the horse's gastrointestinal anatomy is like and just that understanding that we've got a number of hairpin turns, 180-degree turns where just like if you're traveling down a mountain, you've got to slow to get around that corner. The passage of ingesta is slowed in those locations. So they're predilection spots for colic. But then understanding that that kind of impaction colic is going to be different to resolve to a horse that's got a bit of bowel that's dislocated or displaced, sorry, or twisted. So, just understanding that not all colics are the same and so the horse that resolves or responds quickly probably had a lesser problem than the horse that responds more slowly or that needs a more intensive level of care. And that's nothing to do with veterinary expertise or owner fault or anything like that. It's just anatomy and physiology. So understanding that. I guess from an owner's perspective, understanding that the severe colics are painful to the point that they will roll and hurt themselves and they're not going to be careful of you as their handler. 

0:56:43.9 DR: So, just being aware that owners can walk a horse if that will distract him or her by all means, and that may have marginal therapeutic benefit, but just to bear in mind that they need to keep themselves safe in the first instance. And then the other thing would be talking to your vet about preferred treatment options. I mean, I've spoken to owners that are convinced that beer is helpful. In Western Australia, there was Berg oil, which I still don't actually understand what it is. So there are those kind of remedies from the past, perhaps, that are of questionable value. We have a lot of owners that will use phenylbutazone for colics, and I personally don't think that that drug is particularly good at visceral pain. I think it's great for musculoskeletal problems. But I find it a little bit disconcerting when owners have used that for colic, and especially if they've used it more than once. I think we've just got to be aware that it's the definition of stupid, isn't it? Doing the same thing over and over again and expecting a different result. So, just talk to your vet about what you can do as a colic first aid measure, but recognize when you need to escalate treatment early because that's the time that we can support owners to do the best thing for their horses. 

0:58:16.2 DD: Those are so very, very helpful sort of suggestions, concrete suggestions. And as we wrap up, because this has just been so great to talk with you, what's your take-home message for our audience?  

0:58:32.5 DR: I guess the take-home message is that as much as we can to try and keep management consistent so that we don't predispose horses to colic. But then just being very vigilant, because early intervention, if you think your horse has colic, is going to be useful. Preventative care, so appropriate anthelmintic treatment. And again, talk to your vet about what's going to be appropriate to your management situation. Appropriate dental care is probably important, although we're still trying to generate evidence to support the importance of dental care as a preventative strategy. And then if you've got some risk factors for your horse, so, and particularly thinking about sand or coarse quality feeds or toxic plants would be the other thing. There are a few sort of issues there that we can try and eliminate from the horse's environment. So prevention and early intervention would be the take-home message. 

0:59:38.7 DD: Which is always kind of the byword for a lot of things. Well, that does it for this episode of Fresh Scoop. And once again, thanks to Dr. Raidal for joining us from Australia. So we've got about what did we think, like a 16-hour time difference here, to the miracle of Zoom, here we are. So [laughter] we'll be back with another episode next month that we hope you'll find just as informative. The science of animal health, of course, is ever-changing. And we need cutting-edge research information, whether we're treating patients as veterinary caregivers or as pet parents. And that's why we're here. You can find us on iTunes, Spotify, Google Podcasts and Stitcher. And if you like today's episode, we'd sure appreciate if you could take a moment to rate us because that will help others find our podcast. And to learn more about Morris Animal Foundation's work, go to There, you'll see just how we bridge science and resources to advance the health of animals. You can also follow us on Facebook and Instagram. And I'm Dr. Kelly Diehl and we'll talk soon. 


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