Full Transcript: Dog’s Lymphatic System
Scott Groves: Welcome back to another Dog Pod podcast edition. I am not sure what episode we are up to now, but I am your host Scott Groves, and with me, again, is our famous veterinary celebrity, Doctor Kevin Cruickshank. Thanks for joining us again.
Dr. Kevin Cruickshank: Thanks Scott. Good to be with you.
Scott: So this week, I thought we would talk about one of the major health systems of a dog, and to help people sort of understand it a little bit deeper and that is the lymphatic system. I will think a lot of people are familiar with, obviously, the circulation in the blood because we understand that a lot better as human beings, and excuse me, but we have a heart that pumps things around but not so with the lymphatic system. So I thought we talk a little bit about that today.
Dr. Kevin: I think it is a great idea. It is probably one of the lesser-known and lesser understood systems in the body, but it is actually a really core center, so good topic.
Scott: Awesome. So let’s start with, I think, something to help dog owners understand it. Because a lot of us as humans understand that when we get sick, we probably all think back to when we first went to the doctors years ago. They put their fingers on your throat and they feel for lymph nodes being inflamed and those little sort of ball-like parts of our body under your arms and around your neck. They are obviously all throughout our body, but as it probably the first point of reference for human beings, that is probably one of the things that sort of springs to mind for me, how much different is a dog’s lymphatic system to a human being’s lymphatic system?
Dr. Kevin: It is really not that different. The whole process is the same. There will be different locations because the shape of the body is a bit different, but it is quite amazing. There are lymph nodes all over the body. Some of them are really, really small that you would not be able to feel them very much unless there’s a problem and they are enlarged. So, the role of the lymphatic system is it is a big part of your immune defense system. It is the defense to keep your body primarily protected from infections. And then you, unfortunately, often also hear of lymph nodes or sometimes referred to as lymph glands being enlarged with cancer spreading to them, sadly. So they work like a filter for the body and filter the bad things out to keep them from spreading from one part of the body to the other part.
Scott: Okay. In terms of, I guess, the function of it in comparison to a human. I mean, humans’ lymphatic system is very long. Obviously, dogs are a lot smaller animals. So there must be some differences with the efficiencies, I guess, or how it transports or is it just all sort of comparative because dogs are smaller their lymph nodes and comparatively smaller and…
Dr. Kevin: Correct. Yes. It might not be physically as long but it reaches from all parts of the body. Even just…there would be a difference from the fact that humans are standing upright and dogs are standing on all fours. So, people do get edema of the lower limbs more easily than dogs do because edema is when there is fluid buildup in the tissue and a big part of the lymphatic system. The lymphatics work together with the veins to bring the fluid back to the central part of the body, so around the heart. So the fluid and primarily it is the blood together goes out in the arteries and then is used by the muscles or whatever part of the body it is using and then a lot of it returns in the veins, and then a smaller component is separated out and returns in the lymphatics. The lymph vessels are a very thin-walled, very small structure much smaller than the blood vessels, and it is very much a passive mechanism. It relies on the structures especially muscles around it to effectively work like a pump. There are valves in the lymphatic vessels that allow fluid only to go in one direction, but it can’t actually pump and constrict itself. So the muscles and essentially movement and that is where movement and mobility play such a big role in the efficient workings of the lymph system because when your muscles move, they cause a constriction and effectively squeeze the lymph vessels and that causes the lymph to move in the correct direction. At certain key points along the way, you get a lymph node. The lymph node is effectively a big filter and so it filters and fights infection and then the lymph carries on passed through from the node and comes back into the central system and eventually goes back into the heart and circulates around.
Scott: Yeah, right. It’s fascinating and one of the points that you just sort of touched on there is it is a passive system, so it doesn’t have a heart like the blood system has or circulatory system to be able to pump things around, and I guess, we just went for a morning run together as we do before this podcast and we were just chatting. That actually really comes back to the importance of walking a dog every day.
Dr. Kevin: It really does. So it is helping to keep them healthy, even in recovery from surgical wounds. Obviously, sometimes you want them to be still for a little while, but to aid and speed up recovery, gentle, and it does not have to high intensity exercise, just literally walking.
Scott: Gentle walk, yeah.
Dr. Kevin: So as dogs get older as well, anything that we can do to improve their mobility will help improve their immune system effectively because the lymphatic system is going to work more efficiently.
Scott: Yes, interesting. I like the point you made before, too. Something I wanted to circle back to is that the lymphatic system is actually part of the immune system. I would think it is probably not common knowledge for a lot of people that the two are intricately linked. As a dog ages or as they sort of transition, I guess, from that sort of puppy stage and they start to mature, what sort of changes, I guess, happen with the aging process around the lymphatic system, given that the importance of mobility is there? But if a dog was to keep moving, do they just degenerate like all other parts of the body where inflammation will slowly build up over time or the lymph system won’t work as well, or does it really just depends on how healthy you maintain your dog?
Dr. Kevin: Yes. Luckily. We do not notice a specific failure or deterioration of the lymphatic system, but very interestingly, young dogs, it is well known that their lymph nodes are actually larger than when they are in adulthood, so it is not a problem. They are just quite a bit bigger as a young dog, and then they settle down to their normal sort of size. And then yes, if they can be a very strong indicator of a problem, unfortunately, there is also cancers that affect primarily, so they are not a secondary spread to the lymph nodes, but they actually start in the lymph nodes. So that is a disease called lymphoma. So that can be a very important thing to know or notice if suddenly a lot of the lymph nodes are enlarged.
Scott: Okay, with the inflammation you mentioned in humans, you often see humans that are struggling with conditions. They get a lot of fluid retention in lower limbs. What do we look for in dogs? I imagine, dogs still get swelling and still get some sort of fluid retention, but it is a little bit harder to spot being spread across their four legs. Is that what we are…?
Dr. Kevin: Yes, and I think probably we do not have the effect of gravity as dramatic on them. Swelling is intricately involved with your circulation. Heart failure and heart disease is very prevalent in people. It is also very common in dogs, but we do not tend to get as much swelling in dogs as we do have issues in humans. I think some of that is just out of absolute necessity even do go to the toilet, go over to have a drink of water. Dogs have to eat as they age, have to be a bit more mobile than people are as well. So we do not have as many problems of, say, just lying in bed all the time and getting swollen.
Scott: Humans by nature on their feet probably more hours a day than perhaps a dog as well. Dogs typically sleep about twelve hours a day, humans are struggling to get 8. So I imagine that probably the laying down for a dog whilst it is, obviously, the opposite of the mobility we want to get the muscle contraction, but the additional rest they get would stop at pooling, I imagine, in lower limbs like we see in humans.
Dr. Kevin: Yes, definitely because the longer you up on your feet, the more time the body has got to work against that gravity and it really is exponentially different for an adult person standing up the length that the lymph actually has to come from, say, your feet to your chest level compared to for a dog. Even the tallest of dogs are at least half the height of an adult. So, I think that’s an advantage that dogs have there.
Scott: Say, how would a dog owner spot or start to identify information in a dog when it is a lot harder to spot, as you are saying, even for you as a vet. You know what to look for, but what is a dog owner to look for?
Dr. Kevin: It is kind of unexpected lumps. And so that is why having fairly constant, just even pats and cuddles and brushing your dog, you get to know what is normal and suddenly you will notice, “Oh, there is a lump here that did not use to be there.” You might not know that it is a lymph node, but just identifying that a lump is something abnormal and certainly a reason to take your dog to your vet, sooner rather than later as well. Sometimes, swelling and inflammation is very painful. So they might be either licking at that area because the skin is under a bit of tension, uncomfortable or limping on a leg, that type of thing as well. Because very commonly, just the most minor little cut or anything like that can suddenly lead to inflammation and swelling. Something called cellulitis, where you have got an accumulation. That’s not really a problem with the immune system but…sorry it is not a problem with the lymphatic system causing it, but if you can improve the lymphatic drainage, you can improve that swelling, to get it to subside much quicker.
Scott: Okay, interesting. Yes. I forgot what was I going to ask you then because I had a really good question…
Dr. Kevin: Well, maybe something I was going to lead on is just that it’s helpful with recovery of wound healing especially as well. So after surgery, we can sometimes get a little bit of swelling in an area. Either the lymphatics are overloaded or they might actually be partially blocked if there is a lot of pressure from other swelling, again, coming back to the idea that the lymph vessels are passive, any swelling, because of, say, surgical swelling will then block the drainage of those lymph vessels, they would not work so efficiently. So that can really help wound healing if we can do things that enhance the lymphatic drainage as well.
Scott: Okay, that is interesting. I remember what I was going to ask now. Just so we do not freak dog owners out as they are patting their dog and they feel around, and it is obviously not for them to diagnose. That is where a vet comes in handy. But if they find a lump, I think it is probably important that I just initially straight off freak out. My dog has got a tumor or a cancer or a…
Dr. Kevin: For sure.
Scott: From your experience, what sort of things do you see where it is like a benign cyst versus it is an inflamed lymph node, or it is a cancer.
Dr. Kevin: So probably by far, the most common for an enlarged lymph node is that there is actually an infection in that area. So some of the most common ones is that the lymph nodes behind the jaw and that will often it be because of a gum infection. They have got bacteria in their mouth and we may go and look and see, “Actually, this dog needs dental treatment to sort out these.” The lymph nodes are just the indicator of the problem.
Dr. Kevin: Even something as mild as a thorn in its foot that has got a little bit infected might suddenly cause that swelling to come up. But yes, when it comes to other types of lumps, and it could be a whole topic for another podcast. But yes, it is very hard and we often cannot always know with certainty. We do not have x-ray fingers I often joke, and say because some very small looking lumps in the skin can be very serious and a lot of them are quite benign. Certain breed types like the poodles and any poodle crosses, they get a lot of very benign, something called a sebaceous adenoma, and it is a nasty-looking, almost like a bunch of grapes. Sometimes, little lump raised above the surface of the skin. It’s not a nasty cancerous thing, but their skin type is much more prone. As they age, unfortunately, they get them sort of all over the body, and it is not uncommon for them to have twenty, thirty of these tiny little lumps, eventually starts with one or two. Yes.
Scott: As they age, sure. Yes, okay. In terms of locations of these lymph nodes, is it like humans? I mean, they are very strategically placed in humans. In the groin, behind the knees, under their armpits where we get major muscle movement. Is it the same for dogs?
Dr. Kevin: It is, yes, very much the same sort of places. I have mentioned the ones behind the…on the neck. Even there, we might only feel the main one but there’s four or five just in that small area. There you can get a chain of them as well sometimes. But the ones that neither a vet nor an owner will notice is sometimes inside in the abdomen. You have got a lot of lymph nodes in there. Things like an ultrasound scan can reveal what is happening with those, so if you have got a gut infection, you might expect that the lymph nodes internally, you wouldn’t feel it from the outside at all. So those can be enlarged and you actually get them specialized type of lymphatic tissue in the lining of the intestines. There is something called a Peyer’s patch, and so it is actually just a patch. You can hardly feel it but it is actually on the surface of the intestine, so that your immune system, one of the most common areas that they have got is vital for any sort of infections is things that the dogs eat. Nothing sterile that they are having and so the barrier start right there in the lining of the intestine as well. Then, when they have got an infection, sometimes get an enlargement of these areas of lymphatic tissue in the intestines. So if a dog has got diarrhea, for example, it might have quite a lot of inflammation in its intestines from the lymphatics being involved there.
Scott: That is so interesting about the food because it is not something I considered and…I know we will talk food and supplements on another podcast, eventually. Essentially, I mean, like with us as humans, the lymphatic system and immune system is just constantly fighting off toxins and just it is constant…
Dr. Kevin: It really is all the time we challenged and it is working in all parts of the body that you cannot imagine has them. Lymphatics are involved in the eye, they are involved around the brain. There is not a part of the body that they not there in draining away tissue and filtering out the bad things. And then also, the lymph nodes they actually actively get enlarged when they are fighting infection with producing some of the white blood cells that do fight infection and they block things like lymphocytes.
Scott: And dogs will lick everything, too, like your dog, yes.
Dr. Kevin: It is absolutely quite amazing that the immune system can deal with a lot. But sometimes, people think they are indestructible but they still succumb to things a lot of the time as well.
Scott: What about fluid intake for a dog? And let’s maybe categorize them into sort of small, medium, large dogs, but having appropriate water levels and hydration really helps with the flushing of the lymphatic system to be able to expel that. So what is the right amount of water for, let us start with small dogs first. How much should they be drinking in a day to, I guess, help and maintain that?
Dr. Kevin: Yes. I think the key thing is free access to water. We do have criteria to decide “Is a dog drinking too much?” What water level is too much? And the actual technical level is a hundred milliliters per kilogram per twenty four hours. Now, that is actually quite a lot, so if you have got a five-kilogram dog, it is five hundred milliliters, half a litter in twenty four hours.
Dr. Kevin: But the normal level is probably quite a bit below that. Probably approximately half that. But if you were drinking sixty milliliters, it might seem like quite a bit but it is sixty milliliters per kilo.
Scott: Per kilo, you mean? Yes.
Dr. Kevin: But it is–
Scott: Which should be three hundred milliliters per day on a five-kilo dog? Yes.
Dr. Kevin: But it wouldn’t be considered to be too much in terms of deciding whether we start investigating things like diabetes or kidney failure, and the symptoms are that they are drinking excessive amounts.
Scott: So a hundred is excessive, you mean?
Dr. Kevin: Anything above that, yes.
Scott: Anything above a hundred is excessive?
Dr. Kevin: A hundred milliliters per kilogram.
Scott: Right? And that is a bit of a red flag in terms of diabetes or stuff for you guys as vets? Okay, right.
Dr. Kevin: It is a classical exam question. Can you list all the most important things that increase thirst will be indicative of?
Scott: Okay. Alright, so let’s go to medium dogs, then. So is it just the same proportionally per weight?
Dr. Kevin: That would be the same. Yes.
Scott: Okay, so that is nice and easy calculation. So, how would a dog owner track that? I mean, I know we have got a lot more pet tech and that is these days. We have got little water feeders and we got little dog feeders with cameras on it and all sorts of stuff nowadays.
Dr. Kevin: It is a challenge and especially if you have got more than one animal, so it might even be that the cat comes and drinks from the dog’s water bowl as well. Or if you have got two dogs that makes it much more challenging.
Scott: Okay, Yeah.
Dr. Kevin: But what we suggest to people to do, let us keep it simple. Assume there is only the one dog.
Scott: Sure, one dog. One easy dog.
Dr. Kevin: So we fill the water bowl and then make a note of every time they top it up. So then top it up from a jug where you know how much you have added in and note that down. At the end of the twenty four hours, bring it back up to being full again, and through your little diary collection, you know how much you have put in all the time, and that is going to…ignoring a little bit of evaporation. That is going to be sure effectively the amount. If your dog drinks from two or three water sources, just keep recording where you top up every day.
Scott: Okay. Because it’s hard one and like you see a dog licking at a bowl. It is not like us that will gulp stuff down. I mean, that is a lot of licks in a day to get. Yes.
Dr. Kevin: It is, yeah. It is hard for them to get the full amount, but I think that’s what all that they know. They do not know drinking any other way. But yes, it is not a very efficient way of drinking, that is for sure.
Scott: No, it is not.
Dr. Kevin: Not always very clean either. They make a bit of, some dogs more than others, make quite a slobbery mess when drinking from a water bowl.
Scott: Yes, absolutely. So what else would a dog owner be asking or…I mean, I am not sure. It is a topic that comes up a lot with the lymphatic system in the vet clinic as such. But in terms of regular vet checks and consultations, what should dog owners be looking for as, I guess, signs. Whether it is warning signs with inflammation or things like there might be something wrong with one of the circulatory systems be at the blood or the lymph?
Dr. Kevin: Yes. I think it is very hard for a dog owner to monitor that. And that is the benefit of an annual visit. Often combined with our annual vaccination visit is then you have got someone who does know. And often, if we do not mention to the owners that we are busy checking that when we are doing a physical exam, they do not even realize that that is what we have gone and checked. Just in those key main lymph node sites, we will feel those as we go through our physical exam as well because, yes…The most common ones that people notice are the swellings sort of below the ear, on the side of the neck, that people will notice being enlarged or sometimes, it may simply be…they don’t have to be scientific. My dog is repeatedly getting unwell or ill. Succumbs to things very easily. If it is not this infection or is on and off with diarrhea but occasional vomiting that may be a problem that he is having persistent infections and that type of thing
Scott: Right. You had seen like a walking gait and things like that where they may look to be limping or anything? If there was an inflammation issue or things like that or…?
Dr. Kevin: If it was a painful inflammation, but simply an inflammation of the lymph nodes, they are not on their own that painful at all, so they are not likely to make a walk.
Scott: Yes, they just walk through it…
Dr. Kevin: And probably a very nonspecific thing. They will just not be very well, just not as energetic, not as enthusiastic to eat, all those sorts of things. You can’t put your finger on it, but just as a person who knows their dog well, you just know something is not right.
Scott: Right, okay. Because as your lymphatic system becomes essentially more toxic or there is more build up, we become more lethargic.
Dr. Kevin: Absolutely.
Scott: So that is the sign that dogs…
Dr. Kevin: And a big one with dogs is if they have been a good eater and then they are not interested in their food. A loss of appetite is quite a significant symptom for most dogs.
Scott: Okay. Yes, interesting. All right. Well, as always, Kevin, thank you very much. It is always very insightful and it is a lot of great information for dog owners out there. So, if you want to learn more about Dr. Kevin Cruickshank or Gold Coast Vet Surgery, go check them out. All the links are in the show notes, and we will look forward to seeing you in the next episode. Thank you.
Dr. Kevin: Thanks, Scott. It has been a fascinating topic. Thank you.
Scott: Cheers, Kevin!