Hello and welcome to this evening's webinar in which I'm going to share with you some of my top tips for unblocking a blocked cat. And when we talk about a blocked cat, on this occasion, we are of course talking about urethral obstruction and inability to pee, that nightmare emergency scenario that crops up all too frequently. So before we think about how we unblock the blocked cat, let's just think about the sorts of things that might be causing the blockage, because knowing what is causing the blockage will definitely help us in our treatment planning and very importantly in our postoperative treatment planning when we think about how we can prevent the blockage from recurring.
So as you know, one of the most common reasons for a cat to present with urethral obstruction is that it is developed a urethral plug, and this is one of these sticky, gritty, toothpaste like accumulations of debris within the penile urethra, which once you remove it is quite soft and dispersable, but trapped within the urethra can form an absolute plug like a cork in a bottle. We can, of course, also see urethral obstruction because of a urolith. So that is an actual stone, a mineral stone that's formed within the bladder, but then has been able to pass into the urethra, but has not been able to pass all the way through.
So these are stones of a certain size because they need to be small enough to get into the urethra, but large enough not to get out of the urethra. And as we'll see, around about 2 millimetres is the sort of cutoff point. If it's below 2 millimetres, it probably will pass above 2 millimetres, it won't.
But of course, if it's above maybe 0.5 cm, 6 millimetres across, it's probably too big to even get into the urethra in the first place. Those are the sorts of things that we most commonly see causing a de novo obstruction, if you like, but what we can also see as a very significant problem, especially after a cat has had urethral obstruction, has had urethral catheterization and flushing, and so on, is that we can get a period of urethral spasm where the inflamed urethra has gone into increased muscle tone, and that in itself can cause obstruction.
Very occasionally you will see a cat that just simply presents to you appearing to be obstructed, and it will turn out that it does not have a physical blockage, it is indeed urethral spasm. But more commonly, this will occur after some intervention with the urethra, that means the urethra has been traumatised by the original disease process and unfortunately maybe some additional trauma from the unblocking process that then leads to postoperative urethral spasm, which can be really frustrating and difficult to manage, and we'll certainly talk about that towards the end of this presentation. And then finally, a problem which hopefully is is rare, but certainly can occur and definitely is something we need to have an eye to preventing is urethral stricture.
And this is where there is An area of fibrosis, scarring, if you like, at a site of previous urethral trauma. So the cat may have had a blockage. The blockage may have been cleared, but if there's been damage to the urethra and subsequent scarring over weeks and months that scarring can narrow down to produce a strict.
Which forms unfortunately a permanent site for reduced passage of urine and indeed, obviously a high risk of further obstruction if other debris is present. So those are going to be our four main categories, and we will talk about plugs and neuros and how to clear them, spasm, how to recognise it and how to try and reduce it, but also how to try and prevent it. And very importantly also how to approach these cases to unblock a cat without increasing the risk of further urethral stricture down the line.
OK. So faced with a cat that presents to you with urethral obstruction, here is my first top tip number one. It's, I hope, self evident, but let's let's make sure that we highlight it.
Blocked cats are in pain. We always need to provide analgesia, and we should do that as soon as we are presented with the cat and as soon as we recognise that that is what the cat's issue is. Clearly we need to have an eye to what is going to be both effective but also safe to use in a cat with .
Urethral obstruction and therefore potentially acute kidney injury if the pressure in the bladder is enough to be putting black pressure onto the kidneys. So our first line choice in our clinic is to use a combination of butterphenol as a nice rapid onset, but quite short acting opioid. Along with buprenorphine, which is relatively slow onset, but has a nice prolonged duration of effect.
And that combination will provide us with a good level of analgesia for most situations. It can be given IV. Or it can be given IM if we just want to get something on board nice and quickly.
And you can actually combine the two in the same syringe. They do use the same opioid receptors, but because the butorphil goes on quite quickly, but comes off quite quickly, the buprenorphine does have open receptors to bind to, when it's good and ready. So you can use that as a combination.
You may prefer to use methadone, and that's fine. It's nice and rapid onset again, can be IV or IM, relatively shorter duration of action than in other species, and not as long in duration of action as buprenorphine, but as long as you have an eye to topping it up every 4 hours, then that it can be a really good choice as well. And then what about non-steroidal anti-inflammatories?
They do have a place to play for sure, partly because of the analgesia, and partly because, as we've already alluded to, there is inflammation in the urethra and the inflammation can promote further narrowing, and therefore further risk of blockage. So when the cat is well enough to cope with it, we may well want to come in with a non-steroidal anti-inflammatory. But possibly the time when the cat first presents to you is not the moment.
If the cat is dehydrated, hypotensive, azotemic as it is likely to be, then we want to withhold the non-steroidal until we have reversed at least the hypotension and the dehydration and got the cat into a condition where it's not in what is described as a Prostaglandin dependent state, which is the situation in which nonsteroidal anti-inflammatories can become nephrotoxic. So that brings us to top tip number 2. How are we going to move the cat out of the situation of acute kidney failure, in order to get the cat into a better state for anaesthesia and the further manipulations that we're going to need to do for him.
And here's my top tip #2. The most effective way to manage the acute kidney failure is to reestablish urine output, allowing the kidney to go back to doing its job and allowing you to give the cat IV fluids to help to ameliorate the metabolic consequences of urethral obstruction, which I've listed here for you. So we've touched on azotemia due to lack of renal output.
That will also produce hyperkalemia, hyperphosphhotemia. There will be a metabolic acidosis, and if it's been going on for long enough, if the situation has been going on long enough, then the cat will also be suffering with dehydration. So clearly, if we can get the kidneys working again and give IV fluids, that is going to be to the cat's benefit.
And things like hyperkalemia, acidosis, azotemia may well be contraindications for anaesthesia that mean we need to address those problems before we can move forward and safely unblock the cat. Now this is where I appreciate that it gets a little bit controversial and I know there are two schools of thought on this. Suffice to say I'm firmly in the camp that suggests that it is a good idea to empty the bladder by cystocentesis at the earliest opportunity.
The benefits of doing so are the immediate release of pressure from the kidneys so that the kidneys can start working again, and the kidneys are our best friend here. They are healthy kidneys, so as soon as they have the opportunity, they will start to redress all those metabolic consequences that we've just been talking about. I would also argue that in order to effectively flush the urethra clear of whatever is obstructing it, we need to have a low pressure situation in the bladder so that there is space for us to flush fluid into it without further overstretching and causing even more damage, and we can only do that by emptying the bladder.
Emptying the bladder will relieve the stretch on the wall of the bladder, which is a major cause of pain in these cats, but also is causing damage to the nerve plexus within the the bladder wall and promoting post obstructive bladder ay, that kind of floppy, flaccid bladder, which can be a permanent situation if it's been going on for too long, or certainly can be a problematic short term problem after you've unlocked the cat. As I mentioned in in reducing that pressure in the bladder, you will provide analgesia. And of course, you will get a urine sample for future analysis when you have a moment to turn your attention to that.
So multiple benefits of emptying the bladder. Of course, the fear is that if we go into the bladder with a needle, that it might pop like a balloon, it might burst and release urine all over the abdomen, and that clearly is something to be avoided at all costs. I would argue that there is a small risk of doing that, but actually the risk is very, very small, if not negligible, if you follow three golden rules, and the golden rules are keep the cat still, keep the needle still, and empty the bladder completely.
So what do we mean by that? If the cat is wriggly and you introduce your needle into the bladder at the wrong moment and the cat moves, the, the, the point of the needle can score the surface of the bladder. And that will cause a weak, weakness along a line which the bladder may then tear along.
But if you introduce your needle perpendicular to the wall or at a slight angle to the wall and go straight through, then you will not cause an explosive pop like bursting a balloon. So it's really important that the cat is kept still, and for the same reason, it's really important that the needle is kept still once you start to withdraw urine in order to keep that little puncture to the smallest possible size that it can be. So in some cats, if they are really moribund because they have been blocked for so long that they are very aotemic and in a really bad metabolic way, you may be able to keep them still enough just using manual restraint in order to take the pressure off the bladder.
But in the vast majority of cases, I would suggest that you will be able to do a better and safer job if you do give the cat some sedation. Again, we need an eye to what is going to be an appropriate sedative combination for a cat with an at the moment unknown metabolic situation, because this is something that I would suggest we're doing before we draw blood and assess the metabolic consequences and so on. This is part of the emergency immediate management of these cats.
So a combination that we use in our our our clinic is to use a combination of alfaxan, which can be given either IV or IM and butterphenol, but we've already mentioned that we give these cats butterphenol or methadone as standard on arrival. And therefore, that is probably also already on board. So IVLfaxin, or if you don't keep alfaxan, then IV propofol to effect is a very good.
Very well tolerated short acting means of sedating or indeed anaesthetizing these cats to allow you to do cystocentesis in a safe and controlled way, but they will recover very rapidly with no hangover. Other combinations are certainly of course options, things like ketamine and midazolam, if you keep those in your practise, butorphanol midazolam, if you want to avoid any extended ketamine effect, because really what we want to do at this moment is very simply empty the bladder to take the pressure off the situation. We're not necessarily looking to go straight into a whole unblocking process.
So we're not looking to induce a long term anaesthesia. We just want to keep the cat still while we empty the bladder. And then to facilitate keeping the needle still once you start the process, a butterfly needle, and extension set is very helpful so that as you manipulate the syringe in order to draw the urine out, take it off, empty it, or use a three-way tap or whatever, you're not directly attached to the needle so that you can move the syringe around freely without the needle wafting about in the bladder.
And again, that will reduce the risk of post cystocentesis leakage. And then the third thing, which is really important and a huge factor in reducing that risk of leakage, is to empty the bladder completely. Once you have your needle in place, don't be tempted to just take off enough to make the bladder a bit softer and then come out because if there is residual pressure within the bladder, as there will be if it has residual urine in it, that's when you get this effect, as I've tried to illustrate in the picture.
On the bottom right of your screen of urine jetting out through the hole that you've just made into the abdomen. And if you do have the unfortunate situation of causing post cystocentesis leakage and the cat was held nice and still, then it most likely is that the urine is leaking through the hole that you've just made because the bladder is not as elastic as it should be because of the disease process going on. And if you have not removed the urine completely and got a low pressure situation in the bladder, then urine can be forced out.
But if you empty the bladder as completely as you can, and again having the cat well sedated facilitates that, empty the bladder as completely as you can before you remove your needle, then it is a very well tolerated procedure, and as I've alluded to, there are multiple benefits to it. Not least the fact that once you have released the pressure on the bladder, you now have kidneys that are re-establishing output and therefore a situation where you can put fluid into the system because there is a mechanism for getting the fluid out again. So now we can safely.
Start the cat on IV fluids without risk of causing either further filling of the overfilled bladder or worse still, if the bladder won't accept any more urine, we can rapidly get a situation of vascular overload if the kidneys cannot send the urine anywhere. So now we can start IV fluids. Again, in my hands, I would suggest that we use a buffered a buffered solution, so Hartman's or compound sodium lactate, because the bicarbonate will help to buffer that metabolic acidosis.
Even if you're not in a position to measure that acidosis in your practise, we can assume that it is there and the the bicarbonate will help. People sometimes worry about using those products because they do have an amount of potassium in them. But the amount of potassium is low.
It's lower even than the normal level of potassium in the blood, as you know. And so actually we should be supplementing potassium for maintenance use in all situations because the the the low potassium content will still dilute out the serum potassium. So if you have a hyperkalemic cat, And a very low potassium amount in your solution, then you will still have the effect of diluting hyperkalemia because of the disparity between the two levels.
And of course, the kidneys are also kicking into action to clear that potassium very rapidly as well. So it's fine to use Hartman's and I would advocate it. But if you don't have it or you're not used to it, or you just feel a bit uncomfortable about it, then you say, if that's what you have, and that's what you're comfortable with, because any amount of fluid will help to allow the kidneys to do their job, clear the azotemia, get the cat back on track.
And once you've done that, you've now got a cat who is comfortable because you've given analgesia and reduced the pressure on the bladder. The bladder is empty, so you've taken away the strain on the bladder wall. The cat is having fluids, and that can only improve the situation and make anaesthesia when you come to it safer.
So now you can actually get back to whatever it was that you were doing before the blocked cat came in. You can finish your evening surgery. You can even go out on that visit to the calving cow or whatever it is that you should be doing, or you can reach for the notes that you have from that lecture you attended long ago about how to unblock a blocked cat, but you've forgotten some of the details, and it wouldn't hurt to refresh your memory, and you've now got time in hand to go and do that.
Because when we come to the next stage, which is actually finally to get round to actually relieving the obstruction. I would suggest it's really important that you're able to do it in a calm and controlled way when you have time to give to the cat, time to allow as much time as is needed to clear the obstruction. And you're not trying to squeeze this in between other projects, other jobs, people in the waiting room, other people coming at you with with messages and requests and demands.
Because unblocking a blocked cap takes as long as it takes, and the more pressure there is on you to do it hurriedly, the more likely you are, unfortunately, to inadvertently cause damage in trying to clear the obstruction. So postpone the the unblocking process until you have time to give it. And if you need to empty the bladder again by cystocentesis, because it's actually going to be quite a long time before you have that opportunity, then that's fine.
You can go round that loop again, and the longer the cat's on on IV fluids, the better its state will become. So then finally, top tip number 3, how to actually relieve the obstruction without causing further damage. And the top tip here is to consider that we are relieving the obstruction by flushing it, not by forcing a catheter through the obstruction.
So we are going to need a general anaesthetic because we need the cat to be very still and we need the cat to be very relaxed, and we need gentle handling to avoid urethral damage. And as I've mentioned, you need to be patient, you need to take your time, you need to allow the time that it takes. Some obstructions clear really quickly, others take longer, and you don't know at the outset which it's going to be.
But what you do want to avoid at all costs is what is illustrated in this picture here. This is a positive contrast, urethrogram illustrating a cat that unfortunately has has had a urethral rupture because of Let's call it overenthusiastic attempts to unblock its urethra, and the catheter that's been used has unfortunately penetrated the urethral wall and caused this leakage, and this probably happens more often than we recognise because very often the urethra will simply seal up and heal itself without us knowing that we've done this. It may then form a stricture further down the line, or it may not.
We probably very often get away with this without even knowing it's happened. But clearly anything we can do to avoid it is all to the good. So we need to flush the urethra.
I would suggest that you use sterile saline for this.s Saline is quite acidic, which is why it's not necessarily the ideal choice for IV use in these acidotic cats. But for flushing, a situation where the urethral plug is likely to contain struvite crystals, or indeed the bladder may contain struvite stones, flushing with a very mildly acidic solution is not a bad idea.
So sterile saline solution of choice. And very importantly, an end opening urethral catheter, because we need to generate some flush of force and we want it to be in a forward propulsive direction. So catheters that are good for this are things like Kendal catheters or cat cath catheters, or if it's quite a narrow tiny little penile urethra, a lacrimal cannula as illustrated on the top right here is really useful.
You can also get olive tipped catheters, which are stainless steel reusable catheters that have this kind of bulbous end on them, which are lovely because they form a seal behind where the saline is coming out, and they really therefore encourage all of the saline to move forward. If you use a catheter, and I'm going to try and get my pointer up here. If you use a catheter like this one that has side opening ports, then when you flush your fluid in, the the fluid will come out sideways.
It will immediately hit the urethral wall. Some of it will go forward, some of it will go backward, but a lot of the Press that you are applying will be dissipated as the fluid hits the urethral wall and then divides forward or back, whereas what we want is an end opening catheter so that all of the propulsive force that you are applying is pushing the saline forward to clear the obstruction. So we don't want a Jackson's cat catheter at this juncture.
We want an end opening catheter. And then again, as I've alluded to, we need low pressure in the bladder so that there is the best possible grade pressure gradient from us pushing on the syringe plunger down to a low pressure system at the other end of the urethra so that everything can jet forward, picking up the obstructive material and washing it through into the bladder. And again, to facilitate that process, what we also need is a nice straight run.
We do not want the flush fluid that we are putting in, again, I'll get my pointer up. We're putting the fluid in here, in this instance, we would get a really nice push up to here, but. And again, we would lose the forward flow and the kind the obstructive material will tend to just lodge round about here because this is where we have this kind of 90 degree, at least 90 degree, often more than 90 degree bend in the urethra that we need to straighten out by pulling and gently bringing the penile the penis up and back to straighten this out.
And I've got a a kind of diagram in a minute to try and show you that. But it is quite hard to do. If you are struggling to unblock a cat, it is usually because you still have some level of bend in the urethra, even though you feel like you've extended the penis as fully as you possibly can.
And so, and it can be difficult because these are often overweight cats. You have clearly clipped and cleaned the area and in cleaning it, it's become a bit wet and a bit slimy and sticky, and it's all quite difficult to get good purchase on. So another little top tip here, and it sounds a bit brutal, but the cat is on good analgesia and under anaesthetic.
So if you apply either a stay suture or a little mosquito clip to the fibrous sheath of the penis, obviously not clipped right across to obstruct it, but just through the fibrous sheath, you will be amazed how much better traction you get and how with very gentle manipulation it will allow you to move the penis up and back another centimetre or so to straighten out that that bend. So a little diagram here to try and illustrate that and it is a bit complex, I'm afraid. But as you know, in the resting situation, the cat has an internal penis and it's actually pointing backwards if you like, or forwards to towards the head of the cat.
So once the cat's anaesthetized and relaxed, and the penis tends to come out to this position. What we then need to do is to extrude it fully. And so we need to push in just above the penis, below the anus and above the penis.
Push in in that direction to swing the penis out dorsally. Once it's come out far enough, we can grasp it between finger and thumb. And then we can lift and pull it further up and back with a kind of sweeping movement, kind of trying to illustrate that here.
And we're aiming to get the penis up to a situation where it is in a, in a smooth, straight line. So bringing it right up to this position. And as I say, that can be quite tricky to do, but a little stay suture or a little clip here can really help you to do that.
And once you've straightened it out, then we can again address ourselves to flushing, but not forcing the the obstruction out of the way. So we pass our catheter tip into the distal urethra only. You're not trying to pass the catheter right through the obstruction, even if it is a urethral plug.
You don't want to just pass the catheter through it because there will be residual obstructive material around the catheter, which you are not then going to be able to flush into the bladder. So we're going to just pass the the catheter tip far enough into the urethra to to form a nice seal. But not trying to push it right through and into the bladder.
And then flushing with our sterile saline using a small syringe, and I use a 2.5 mil syringe at this point while I'm trying to clear the obstruction. We can switch to a bigger syringe when we want to just fill and empty the bladder to flush the bladder out, but at the moment we want the maximum pressure we can get.
And so a little 2.5 mil syringe with an end opened catheter well lubricated. So that when we do feel the give and the obstruction is hopefully washed back into the bladder, then we can gently advance the well lubricated catheter.
And what you might find is that you've only shifted the obstruction back a few centimetres, or you might find that actually you can now pass your catheter all the way into the bladder. But as you're passing that catheter, keep a really close feel on it. If you feel any points of resistance, if you feel any little grating areas or any little popping areas, then that tells you that there is still material in the urethra that you haven't cleared yet, and you do need to clear that.
So if you feel any resistance or grating, or as I say, sometimes you just feel a little kind of popping sensation. Then you need to withdraw the catheter distal to that and do more flushing until the urethra is clear. And if in so doing you fill the bladder right up, then you pass the catheter in, you empty the bladder out, but again you bring the catheter back distal to any obstruction, any grating, and flush again until it's really clear.
And once we've done that, we can now try and wash out the fairly noxious, nasty urine, blood, and content of the bladder. So we can fill the bladder with sterile saline. We can empty it.
The first lot will often be very ugly in its in its colour and appearance, but gradually as we repeat that process, we start to find that the fluid comes out quite clear. And what we're doing by doing this is we're flushing out blood and inflammatory debris. We're reducing the the specific gravity of the urine content to try and help to dissolve any other bits of mineralization that's in there.
But you need to be aware that what you will not achieve by this, even with your end opening catheter, you will not be flushing out the kind of gravelly sandy sediment that is often present in the bladder. That will not suck up through your catheter. It will just sink to the the the the most dependent part of the bladder, and you will be sucking off the supernatant and adding more and sucking off the snatant, but you will not remove any significant amount of that sandy debris.
So we'll come on to what we do do about that in a moment. But for the moment, we just need to make sure that we have indeed expelled everything that was stuck in the urethra into the bladder, so that we can then consider how we're going to deal with it from the bladder. So once you feel that you've flushed and your, your, your flush fluid is now coming out clear, fill the bladder up one more time with sterile saline.
Remove the catheter from the urethra and gently apply pressure to the bladder to try to express a good stream of urine. And if you have successfully emptied, expressed cleared the obstruction, sorry, if you have successfully cleared the urethral obstruction, you will now be able to express a really good stream of urine with just moderate and gentle pressure. If it is difficult to express the bladder with the cat under anaesthetic, then unfortunately what that tells you is that you do still have something in the urethra that is stopping you from expressing a good normal stream.
And the same applies if even though you do get some urine out, it's a thin or eccentric stream rather than a really good normal gush of urine. And it's, it's depressing and it's disappointing and it's a bit of a heart, heart sink moment. But the truth is that if you cannot express that bladder fully or and efficiently, there is still something in the urethra that needs to be cleared.
And so we need to go. Back to our flushing, and you try and identify where that issue is and go back to flushing until again, we've got no grating, popping or resistance, and we can express the urine in a really good stream with minimum pressure. OK, so now we're relieved.
We've we've we've relieved the obstruction, the urethra appears to be empty and it's really tempting now to say, thank goodness, job well done, wake the cat up, and away we go. I think we need to just take a further step though. We need to think what is left in the bladder and how is that going to disperse?
How am I expecting what is left in the bladder to get out of this cat? Because if what we had was a urethral plug, then they will disperse when we push them back into the bladder, because they're essentially a mixture of inflammatory mucus, cells, and urine crystals, which, as I say, is is not going to leave a permanent, a permanent stone once we flushed it back in. So if we know that we were dealing with the urethral plug.
Then once that's been dispersed, all those remnants can pass through our now patent urethra, so we can take the catheter out and wake the cat up. If we have tiny euralists, there's kind of sandy sediment that we've talked about, which may be either struvite or oxalate, we probably don't know which at this stage. Those won't be retrieved by the catheter when we were flushing the bladder.
They will still be in the bladder. They will pass through a patent urethra if they're less than 2 millimetres in size, but if there's a lot of them in the bladder, then we don't really want to leave them all there because they are a potential for future obstruction, especially when the urethra is a bit inflamed and probably has increased tone in the days following our procedure. So these little stones, we can identify them because they will show on ultrasound.
They won't show on radiographs because they're too small. But if you apply your ultrasound machine, then you will be able to identify them. And the picture here shows an accumulation of these little sandy stony sediment forming a little disc here, a kind of plaque-like thing, and I hope you can see that there is shadowing behind, so we know that this is mineralized material.
If you, if you block that that bladder, if you kind of shake the bladder to stir it all up, that that layer of sediment that we're looking at here will go up into the bladder like a kind of snow globe snowstorm and form a whole array of little sparkly echo. Genic particles, which will then very rapidly sink back down to the most dependent point and form this raft, which now that it's a whole pile of these little tiny stones is big enough to obstruct the ultrasound rays and give you that classic shadowing behind. What we do need to distinguish though, is that there are other things that can cause sparkliness in a bladder of a cat.
And one of the most common things is that you can find a significant amount of lipid deposit within the urine. Lipid will also look sparkly and bright white on the ultrasound, but lipid will float. It will float and stay in suspension.
It will not gradually sink down, and it certainly will not form this, this kind of plaque at the bottom. The other thing that can look very similar to this on your ultrasound and again will stir up when you shake the the bladder is bits of blood clot and inflammatory debris. Blood clots will look quite similar to lipid droplets in the in the resting bladder, but the difference is that blood clots will very gradually sink down through the urine and will gradually move their way down to the dependent part of the bladder, not as quickly as mineral stones, and they will not form a plaque that form.
Shadowing, but they will fall quicker than lipid, slower than minerals. So you can distinguish on your ultrasound whether you're dealing with blood clots, whether you're dealing with sandy sediment, or whether you're simply dealing with lipid, although by the time you flushed the bladder with saline, you should have removed most of the lipid, so that shouldn't be too much of a confounding factor. So your ultrasound can absolutely help you to know what's left in the bladder.
And if you do have an accumulation of these tiny little sandy sediment stones, I think it is really helpful to try and clear those before you wake the cat up. So we use a technique called voiding hydropulsion for this. It sounds, you know, it sounds quite involved.
It's actually very simple. It's really just a matter of expressing the urine through the now patent urethra and flushing those little stones with the with the urine or indeed the saline. So fill the bladder with saline.
And then we want all of the sediment to kind of collect in the neck of the bladder and in the proximal part of the urethra, so that when we express the bladder, it all gets washed out of the cat. So we kind of suspend the cat for about a minute with its bladder filled with saline, so that all of the stones and sediments settle into the neck of the bladder. And if you've got a small cat, then you may just be able to literally hold it up under the armpits and dangle it for a bit.
If you've got a big heavy cat, and especially as you've also got an anaesthetic circuit that you need to keep an eye on and an IV line and so on, it can be helpful just to kind of drape the cat over the end of the. It looks a bit a bit undignified, but it it it's an effective way of allowing you to support the cat's thorax and head and GA tube and so on, but still get gravity on your side to get the stones to to accumulate in the neck of the bladder here. So that when you now express the bladder quite firmly into a kidney dish, which hopefully you have an assistant standing by to catch what you squirt out.
Then you can get a surprising amount of sediment out of the cat and into your kidney dish. The more of it that's out of the cat, the less risk for future obstruction. But also, this sandy sediment is a lovely sample for you to now send off for analysis to know whether this cat has struvites which need to be prevented in the future, or whether they are oxalates that need to be prevented in the future.
Now we've said that the stones that are less than 2 millimetres will pass through, stones that are more than 2 millimetres may lodge. So you do need to now ensure that no stones have lodged in the urethra. And so we're going to flush that urethra one more time to make sure that it is now still patent and clear of any grating, popping, resistance, whatever, before we move on to recovering the cat.
And if you have got a little stone that's blocked there, worry not. It's only just gone in, it will flush back out into the bladder very easily. You will not be back in the situation of a really heavily firmly blocked urethra.
So for urethral plugs and for tiny stones, once we have expressed those tiny stones, and once we have dispersed the urethral plug and we have a good stream of saline on gentle expression of the bladder. I would advocate leaving the urethral catheter out in these cases because stitching it in is going to add further trauma and further distress for the cat and potentially extend the amount of time the cat needs to be with you in the hospital. That catheter's going to have to come out in the end.
If you've cleared the urethra and you've cleared the bladder as effectively as you can, there's little benefit to suturing in a catheter. So if you're happy that you've cleared as much as you can and that there aren't any moderate sized stones left in the bladder, leave the catheter out. We do tend to use urethral relaxants.
You can think about using ACP or diazepam during the procedure while the cat's asleep in the kind of acute phase for post op. Recovery period, we tend to recommendraoin trade name hypervase, which is a human antihypertensive, but it's essentially a smooth muscle relaxant. So it causes vasodilation and hence the effect on blood pressure, but it also helps to relax the the the the the urethra.
And you can use that for several days. It works on quite quickly, and you can use that for several days in the post-op period. Clearly taking cognizance of the need for analgesia in that post-op period and usually keeping the cat on IV fluids for around 24 to 36 hours post procedure because of the need for post-obstructive diuresis as the kidneys kick back into life and clear all the metabolic consequences that we alluded to earlier.
So we do generally keep these cats in the hospital on their fluids and their analgesia overnight. It allows us to make sure that they can pee effectively. If they can't pee effectively, we can empty them by cystocentesis while the urethral spasm and and inflammation subsides.
But we try to avoid indwelling urethral catheters in these cases, if we possibly can. What about if there are still stones in the bladder though? If there are urists that are more than 2 millimetres diameter, you may be able to see them on your X-ray, you certainly will be able to see them on your ultrasound.
If they are large enough, they will stay in the bladder, and although that may be uncomfortable for the cat, and it may cause a degree of hematuria, at least these larger stones are not a risk of future urethral obstruction. So we've got a bit of time on our side and we can plan to either dissolve them by medical management if we believe that they are struvites, or we can remove them by cystotomy if we are concerned that they are calcium oxalates. The problematic stones are the ones that are too big to pass through with voiding hydropulsion.
But small enough that they may pop into the urethra, and you can see in this picture here that we've got an accumulation of little stones here. These are likely to be calcium oxalates because they're quite bright white, they're quite sharp edged, and they're multiple small stones. You can see here that one of those stones is already creeping in to the neck of the bladder and into the proximal urethra, and is a potential risk for future obstruction.
Likewise, and you may not be able to see it too easily here, but there is an accumulation of stones in this bladder, but there is also a little stone here in the urethra. So these are the difficult ones, and these are the ones that are the highest risk for repeat obstruction. If they are struvites, they will dissolve really very rapidly in the bladder if they are bathed with acidified urine.
So in this situation, you should be able to place an indwelling urethral catheter for around 48 hours or so. Start the cat on a saline drip if it will eat it, use an acidifying diet. But the saline drip alone will be sufficiently acidifying to produce acid urine, which should dissolve those tiny stones really quite quickly.
If you can see them on your ultrasound or your x-ray, then you can of course monitor a few days down the line to make sure that they have been reduced and lost before you then remove your catheter. Be aware though that struvites in the urethra will not dissolve. In order for a stone to dissolve, it must be bathed in urine, and the ones that are in the urethra are not.
So this is not a way to clear any residual material that's left in the urethra. We do need to flush everything back into the bladder to allow it to then dissolve. And of course, calcium oxalate stones will not dissolve.
However, whatever we do with the urine. So in that situation, we are going to need to remove those stones via cystoomy, and I would suggest that we use an indwelling catheter in the cat to prevent those stones from going into the urethra so that we can then proceed with a cystoomy at an appropriate time and place when we've had informed consent from the owner and when the cat is in shape to cope with that. Even so, even if you have got an indwelling catheter, you still need to absolutely double and triple check when you go to do your cystoomy that you do not have any little stones left in the urethra.
You absolutely need to still check for that. But having your urethral catheter in in the interim will buy you the time to then go ahead with the cystoomy in a planned and controlled way. OK.
So just a word on indwelling catheters. I've mentioned that we avoid them where possible. When we do need to use them, we use them for the minimum effective time.
The advantages of an indwelling catheter are that they will maintain a patent urethra while inflammation and swelling subsides. And of course they will prevent re-obstruction if there are small stones remaining in the bladder. But if there is still material in the urethra, an indwelling catheter will not help to clear it.
It will not help to dissolve it. That material will still be there when you take your catheter out after however many days you leave it in for. So they are not a substitute for completely clearing the obstruction.
And if you have completely cleared the obstruction and the bladder is now clear, then there is no need to keep the indwelling catheter in. Because the disadvantages of an indwelling catheter, unfortunately are many. They will be painful or at best uncomfortable for the cat, and they are a major risk for postoperative urinary tract infection.
So in terms of trying to have a comfortable system for the cat, if you do need to place one of these catheters. Then we need to use something that's pliable and non-irritant and as soft and floppy as we can so that it's as comfortable as we can achieve. You can now get 5 Foley catheters, tiny, tiny Foley catheters that you may be able to pass into the bladder of the cat if the cat is not too big.
And if you can get them right into the bladder and inflate the bulb, then you may not need to to suture the catheter to the prep use and clearly that will massively assist in making this more comfortable for the cat. But assuming even that you are going to have to suture it in, it still needs to be a catheter that is appropriate for long term indwelling use. And in the UK the the brand names that are suitable are Miller, Miller, however you want to pronounce that, cat cath and these foley catheters, as I've mentioned.
Jackson's catheters and slippery sound catheters, are not useful and not appropriate for suturing into place. So again, you might be you you you likely will be using a very different catheter to suture into place once you emptied the cat, compared to a catheter that you might be using to unblock the cat. So we like to use A candle in order to unblock them or an ophthalmic cannula and then remove that and replace with a myler or a cat calf.
And again, I kind of touched on it already, but these are often big fat cats, and we do need a catheter that is long enough to reach right into the bladder. If you've got X-rays of the cat, you can use those to get an estimation of the distance that you need and the length of catheter that you need to make sure that the tip of the catheter is indeed in the bladder and not somewhere in the pelvic urethra. So they will be uncomfortable.
They will also increase the risk of iatrogenic urinary tract infection. They do provide a kind of motorway for bacteria to access the bladder. So we need aseptic handling for placement.
We obviously need a wide clip and a clean and good sterile technique when we're placing these catheters. If we can, we're going to use a closed collection system. So we're gonna screw a a a a give it a fluid giving set or collection bag to the the cannula.
But of course the dra that that will pull and drag on the catheter. And so, if you can find a way to tape the cat the tubing to the cat's tail. Then that may help with that particular issue, but even so, as the cat moves around, they do very easily twist.
They can kink, they can twist, and they can obstruct such that the bladder still can't empty, even though you've got a tubing attached to it. So they do need close monitoring, they do need careful handling. And if you've got a cat who is really resenting that handling and is constantly twisting and tying it up and and causing problems, you may want to think about actually not using a collection system, but allowing open drainage.
Now you're going to have a lot of urine being produced from this cat and dripping out of this catheter, so it's going to need a lot of nursing care. You need to use bedding like vet bed that will wick the urine away, frequent changes of bedding, really good nursing care, in order to keep the cat. Dry and comfortable as you can while it gets through this this period.
But for some cats that keep blocking and twisting and are in a lot of pain with their perineum and won't let you near to handle to untwist the canyon, the catheter, then open drainage is worth thinking about. And when to use antibiotics again has been a bit of a controversial option, but I think we do now have good consensus of opinion and good guidelines on this. So we do need antibiotics after removal.
I should say that even if you've got a closed collection system, That does not mean that that bacteria can't get into the bladder. Bacteria will go up the outside of the catheter just as freely as they would go up the inside of the catheter. And in fact, both in humans and cats, bacteria.
Migrating up the outside of the catheter is a major source of UTI. So even with your closed collection system, this is still a significant problem. And of course, the longer the catheter is in place, the more likely it is that the cat will have a urinary infection at the end of it.
So we do give antibiotics after removing the catheter, but not before. If we give before, we are simply going to increase the chance of a resistant infection getting established. So remove the catheter and then an empirical choice of antibiotics, usually amoxicillin clavulinate, pending urine culture.
And then, sending a urine sample for culture in order to identify whether there is indeed diatrogenic infection. If so, what the organism and what the most effective antibiotic. Used to talk about taking the tip of the indwelling catheter and sending that for culture.
That's not recommended. It's it's not as sensitive as as using a urine sample. So just a standard urine sample once you have removed the catheter, but an empirical choice of antibiotic until you get that urine culture result back.
OK. So that brings us round to the post obstructive period, when we hope that we have resolved the cat's problems. But top tip number 5, what happens if the cat still can't pee after it has been unblocked, and I know that that unfortunately is a common enough scenario.
And the two most likely explanations are either that the cat is suffering urethral spasm, because it's poor old urethra has had a bit of a traumatic time. Or it may be the cat has re-obstructed because there was either material left in the urethra or there was material left in the bladder which has now moved into the urethra. And of course it's very important to know which is which because the approach to management is going to be very different.
So how do we distinguish urethral spasm from re-obstruction? Urethral spasm is increased muscle tone and so muscle relaxant will alleviate it. So urethral spasm will be relieved by anaesthesia.
And an easy way, therefore, to tell is when the cat has got a full bladder, and obviously it has got a full bladder because you're concerned that it's re-blocked. So the cat has a full bladder, give it a very short term, bolus of anaesthetic induction again, IV propofol, or alfaxolone. The cat is probably already on buprenorphine or methadone because it's post obstructive.
So some IV propofol to effect or IValfaxol alone to effect. And when you do that, if it's urethral spasm, it may even leak out onto the vet bed as you as you anaesthetize the cats, or if not, again, gentle pressure on the on the bladder should produce that really good stream of urine because the urethra is not obstructed. If when you go to squeeze, you cannot get good passage of urine.
There is resistance to flow, then you do have obstruction still in the urethra, even if a urethral catheter passes freely into the bladder. It's actually very common to be able to pass the catheter in one direction, but not to be able to express urine in the other direction. And that can happen because there's a urethral stricture which your catheter can freely pass through.
Or if there is a urolith lodged in the intra pelvic urethra, which you can see from this positive contrast urethrogram, the penile urethra, as we're familiar with, is a very narrow little tube, but look how wide the intra pelvic urethra is. And so it is actually very easy for there to be a stone stuck up in this area which your catheter can pass round, but when your catheter is pulled out, it acts like a kind of ball valve, and when you squeeze the bladder, the stone blocks the urethra. I should say the arrow here is pointing to a little tiny urethral stricture.
I hope you can see that there. And that has formed at the classic point for it to form. It's at the apex of the bend in the urethra.
And it's formed at that point because someone tried to pass the urethral catheter without fully straightening the bend, so the catheter got to here and then it didn't smoothly go round the corner. It tried to keep going in a straight line and it penetrated the urethra at that point. And as I say, that probably happens more often than we recognise and very often will self heal, but we'll leave that little bit of damage.
OK, so back to those, those stones that lodge in the pelvic urethra. Here's another positive contrast, urethra again, exhibiting just how wide the urethra is in the intra pelvic area before it narrows down through the perineal area and down through the penile urethra. So very easy for stones to get lodged in this area and very difficult to see them on X-rays because on your lateral X-ray, the pelvic bones overlie them and even on your VD X-ray, the the urethra is midline and so the The spine overlies the the urethra.
So this is an X-ray taken from a cat that we saw that had had multiple attempts to alleviate its post obstructive obstruction. A catheter passed very freely into this cat, but you could not then express urine, and indeed he could not pee. The plain X-ray looks benign enough, but when we turn him around and we take oblique views, you can see this huge stone which is lodged in this intra pelvic part of the urethra.
A catheter can pass over and round it, but urine cannot be pushed back the other way. They're very problematic, these stones, but at least if you know that's what's there, you can start to look at surgical approaches to alleviate it. So I've shown you there are a couple of examples of positive contrast, urethrograms.
It's not a technique that fortunately, we need to do very often, and it's not the easiest technique in the world. But when you do have these problems with post obstruction. Obstruction, and it's not spasm, then they can be very helpful for identifying urethral strictures and indeed, stones that are still lodged in the urethra to help you with surgical planning or planning your way around that issue.
So I thought I would just share a couple of words about them, as I said, they're not the easiest, they're not the easiest technique. You do need the cat under general anaesthetic. You need to position your cat under under under the X-ray beam and ready to go, and it does help to swing the the hind legs forward.
As far as you can in order to expose this region here, because that's often the area you're interested in, but you may well, of course, need to also take a view with the hind legs extended in order to view this part of the pelvis and certainly you may need to do some oblique views as well. And that may mean you have to repeat the procedure a few times because positive contrast does tend to leak out quite quickly. So you're going to need to really pay attention to your radiographic local rules and safety.
If it allows you to wear a lead apron and gloves and be in the room, then this is a procedure that you can consider. If it, if your local rules do not allow that, then I'm afraid this is just not something. That you're going to be able to do, and you will need to think about referring the cap for CT or fluoroscopy in a centre that has those kinds of facilities.
But if you are able to wear lead apron and gloves and really take full care and credence of the local radiation protection rules, you need to pass your catheter into the urethra. And what you're going to do is use a mixture of iodine contrast, medium and saline that is, is concentrated enough that you can see it, but watery enough that you can easily inject it. And around fifty-fifty dilution usually works quite well for that.
So then you're going to inject your contrast medium. While you are withdrawing the catheter, so that's what we're doing in, in this, in this X-ray here. The catheter was placed.
The contrast was dribbled in as the catheter was removed, and then at the point that the tip of the catheter exits the tip of the urethra, you ask your assistant to take the picture. Obviously stand as far away from the cat as you can, make sure you've got lead gloves and again. Attention to your local rules.
But you can see that you do get a dribble of of a contrast in your catheter. You can see a bit of a filling defect here, which may be a strap trapped stone or maybe an air bubble. So you may need to repeat it a few times to make sure that any apparent lesions are consistent.
That's the most straightforward way to do the technique, but it gives you less good films. Another nice way to do it is to do avoiding urethrogram. And here what we've done is fill the bladder with our mixture of contrast medium and saline.
Then we take the catheter out. And then we position the cat under the X-ray beam, and we, we essentially expressed the bladder. But of course you can't do that just with your hand because you would be right under the primary beam.
So please do not be doing that. You need to find some sort of Described radiolucent paddle in order to express the urine. And by radiolucent paddle, essentially what we mean is a wooden spoon or a wooden spatula that you would use, in your frying pan at home.
But with a long handle, so that you can apply some pressure to the bladder from a distance and push the contrast medium through the urethra. And that's how you will get these nicer images with the urethra really full of contrast and be much more reliable at identifying genuine deficits. But again, it is challenging to do within the realms of appropriate radiation protection.
So, as I say, if CT or fluoroscopy is an option, then that will probably be the better option for some of these really problematic cats with post obstructing obstructive obstruction. But again, you're going to try and take your X-ray as the urine and contrast leaks from the urethra so that you know that you've filled the urethra as fully as you can. So they're tricky.
We don't do them very often. I don't advocate doing them unless you really don't have an alternative. And if you are attempting them, please make, make sure you follow all your local rules as fully as you need to.
OK, so much more commonly, we will find ourselves trying to manage urethral spasm because we have a cat who's struggling to pee after being unblocked, but when we anaesthetize or heavily sedate him, we can express a really good stream of urine. And hopefully, in most cases you can effectively flush the urethra to get to that point. So urethral spasm can be a cause of obstruction, in its own right, but more commonly is a complication of our catheterization and unblocking.
So minimal intervention is really the way forward. Clearly, the more we handle that urethra, the more indwelling catheters we put in, the more we pass catheters through that urethra in order to try to see whether it is spasm or whether it is still blocked, the more we promote more spasm. So we talked about ways that we can try and minimise the chances of urethral spasm by avoiding indwelling catheters, by using gentle handling of the urethra and flushing, rather than forcing a catheter through an obstruction.
And of course, appropriate analgesia. And this is where our anti-inflammatories absolutely come in once we have the cat in a non-aotemic non dehydrated state. Anti-inflammatories will help to reduce urethral spasm.
And if we do have spasm, then we talked about using ACP during and after the procedure as long as it doesn't sedate the cat too much, potentially diazepam or midazolam during and after the procedure again, as a muscle relaxant. Prazicin I alluded to is Hypova dose of 25 to 1 mg per cat peros 2 or 3 times daily. It works on nice and quickly, and you can use that for a number of days post procedure.
But of course you don't want to overdo it and cause hypotension, so just keep an eye on the cat's blood pressure while it's on the hypophase. If you're using the lower end of the dose range, it it isn't generally an issue, but just keep an eye for that. Diennyin for oxybenzammine is another drug that's often used in this instance, 0.5 to 1 mg per kilogramme twice daily.
It's trickier to give to dose because it comes in capsules that are contain much more than you need because they're human capsules and so you need to try and fractionate them down. But also be aware, it can take up to 5 days to reach full effect. And really this is a drug that we need.
This is a situation that we want to be on to straight away. And that's why we recommend Prazin. It's easier to dose because it comes as a one milligramme tablet.
And it's quicker to take effect. So I think it's a better, a better option. And really try to avoid passing a urethral catheter in order to either empty the bladder or to establish whether you do or don't have spasm.
That's why I like the option of expressing the bladder rather than catheterizing. So you may need to use cystocentesis to maintain an empty bladder until the spasm passes if you're confident that it is just spasm. And we talked about the ways to make cystocentesis safe, keep the cat still, keep the needle still, empty the bladder completely.
And again a role for non-steroidals once the cat is well hydrated and not aotemic. So there you are, my top tips for unblocking blocked cats. #1, pay good attention to analgesia.
2, empty the bladder as soon as you can to allow the kidneys to do their job. Very importantly, we're going to flush this urethra. We're not forcing the catheter through or past the obstruction, because that will increase the risk of urethral damage, and it will also leave residual matter around the catheter that is still there and will still be there when you remove the catheter.
So it doesn't in fact achieve the end that we need. Once we have flushed everything back into the bladder, we need to consider what's left in the bladder. Urethral, .
Urethral stones that are less than 2 millimetres, we will be able to remove a lot of them by retrohyd propulsion. We will be able to dissolve struvite stones really quite quickly if they are, if they are small enough to be a risk, then they will dissolve very quickly once they are in the bladder and bathed in urine. But if they are oxalate stones, then we will need a cystotomy to remove them.
And as I mentioned, urethral plugs will disperse once you flush them back into the bladder, and their their constituent parts can be passed by the cat without further need for intervention. And if the cat appears to re-obstruct after you've unblocked it, if the re-obstruction isn't resolved by anaesthesia, then it isn't urethral spasm, and you do need to go in and identify what is left in the urethra and how you're going to remove it, whether that's by further flushing into the bladder, or whether it is a stone that's lodged or a stricture that may need surgical attention. But urethral spasm.
Hopefully if we apply these principles and we are gentle in our handling of the urethra, then hopefully urethral spasm will be relatively mild and will resolve quite quickly in that post operative care period. OK, so thank you very much for your attention. I hope some of that has been helpful.
I hope there's a few little ideas, tips and tricks there that might help to make life a bit easier the next time you're faced with one of these cats. There may be a bit of food for thought there in terms of whether to use cystocentesis or not, whether to use indwelling catheters or not. But as I say, I hope it's been helpful.
Thank you very much.