Good evening everybody and welcome to the second part in this subs lecture. My name is Bruce Stevenson, and once again I have the honour and pleasure of chairing the 2nd session. I don't know that we've got any new people on, but just a quick little bit of housekeeping.

Any questions, click on the Q&A box and we will carry those over to the end. And Benno will answer as many of those as we have time for. So for those of you that weren't with us a few weeks ago when Beno did part one, remember the recordings are online and this recording will also be on the webinar vet website in the next 36 to 48 hours.

So Beno is a graduate of the National Veterinary School of Toulouse in France. After one year of clinical pathology specialty internship in Toulous, he moved to Canada. Sorry, Canada.

Initially as a rotating intern at the University of Montreal, then as a rotating intern at the Ontario Veterinary College. He subsequently completed his small animal internal medicine residency and a PhD at the Ontario Veterinary College. Beno is a diplomat of the American College of Veterinary Internal Medicine.

Prior to his appointment at the UC Davis School of Veterinary Medicine, Beno worked as a clinician in small animal internal medicine department at the Ontario University College, as well as at the University of Montreal, as well as in private practise in both Ontario and in Quebec. His area of interest includes haematological and immune mediated disorders, bone marrow diseases, as well as urology, nephrology in companion animals. Beno, welcome back to the webinar vet.

And again, it's over to you. Thank you. Thank you very much, for this introduction.

So again, saying this disclosure as last time, I'm still French, I still have an accent. So if there is anything you don't understand, please, write in the questions and I will go over it at the end. Obviously, if you have any other questions through the, through the seminar, write it as well, and I will be very happy to discuss that with you at the end.

So I'm just gonna go very briefly about what we discussed last time. The first part of this webinar was about the diagnosis of foetal neal obstructions and the fact that it's quite challenging, that there is no perfect test, but probably ultrasound, and ultrasound combined with radiographs was probably the best way to achieve . a certain diagnosis, but it still remains a presumptive clinical diagnosis for, for some of these cases based on their presentation, the clinical pathological data, and the imaging findings.

And just to remember that time is nephrons and after 24 hours of ureteral obstruction, you're gonna develop an acute kidney injury due to the overpressure within the kidneys, and that will lead to a 40% of a nephron loss. Within 24 hours. So we have some options for medical management, which will be discussed today, but often we have to jump into the surgical decompression with the new gold standard that we want to discuss tonight about subcutaneous ureteral bypass.

So I'm gonna introduce Yukiko again. She was kind of the closing case from the first webinar. She's gonna be the opening case of, of this one.

So she was a 4 year old female spayed rag doll who was presented to me after having been, having been hiding from our owners for about 3 days. She had one episode of vomiting. She was a bit anorexic, she was mostly just not moving much, not willing to go to the litter box, and prior to that, she had never had any concerning medical issues.

On physical examination, she was quite cut, she had a kept coat, she was mildly dehydrated, she had pale thick mucus membranes. She had a very mild heart murmur. But the remember of, the remainder of her tho thoracic auscultation was normal.

Her abdominal palpation showed a mild discomfort with a very smooth kidneys, and there was no, there was no palpable bladder. So initial blood works showed a very severe azotemia with a creatinine of 2,114 and a severe hyperkalemia with a potassium of close to 9 on an in-house biochemistry machine. We had performed some radiographs for Yukiko and if you remember, we could see stones in the kidneys, the ureter, as well as stones in the bladder.

And we performed an abdominal ultrasound that showed a bilateral elic dilation and bilateral. Distension of the ureters with here you can see the pic cavity that is distended, the black being the fluid, and here you can kind of follow the ureter over there, and here you have a stone which is acoustic shadowing underneath. Just again, as I remember, when we talk about feline ureteral obstructions, the etiologies that have been reported are lithiasis in most of these cases.

Stretchers are coming, second, and then we can have a combination of lithiasis and strictures, the story being that probably the stretcher is the location of a previous stone that ended up passing but has left a scarring tissue where she was before. Infection has been described as the primary, cause for the obstruction, probably due to like fibrin clots that are obstructing the ureter. Then there are some case reports of dry solid defined blood clots, circumcable ureters, so an abnormal anatomy of the ureters which is much more detailed in the previous webinar, and some other rare conditions, in cats.

Regardless of the aetiology, the resulting problem is an acute kidney injury, secondary to pressure nephropathy, and again there is a detailed kind of presentation of these AKI and their progression in the first part of the webinar. So in terms of management, we basically have two options, either we do medical management and we try to get the stone to pass, to relieve the obstruction, or we have surgical options to try to You relieve the obstruction mechanically either by removing the the stone, which is what has been done historically and, and what would probably come to mind first or using some more advanced . Tools such as stent, which are an intraluminal device that we can place, up the ureter or subs, which are a bypass of the ureter, so an artificial ureter going from the kidney to the bladder.

So if we dive into the medical management, it has to be initiated following the diagnosis of the obstruction, and actually if we are realistic, it's probably gonna be initiated. While we perform the investigation to confirm the obstruction. In an old retrospective study, 17% of the cats with stones have shown a movement of the stones, which is good.

However, less than 10% of this cat had enough movement to. Pass the stone into the bladder, which means that yes, the stone is moving, but regardless, whatever you do to make that stone move, you keep entertaining the pressure nephropathy and the persistent IKI that is resulting from it. So the recommendations are probably to initiate that medical management while you perform an investigation to stabilise your patient, but to allow yourself only a short time frame, which varies depending on the patient and the clinician between 24 and 72 hours.

During that time, it is recommended to use ultrasound and biochemistry, electrolyte measurements to clearly monitor your patient as closely as possible because obviously if your patient keeps worsening fast, you probably want to move on to something else than the medical management. If there is no amelioration I should have written, I guess, on a worsening in the azotemia, then another intervention is required. However, this medical management remain mandatory in order to stabilise your patient, assess your patient, and make him the most stable you can prior to anaesthesia.

The, the goal of the medical management is like for any AKI to try to prevent progression of AKI from being a sublethal to a lethal injury. And In order to do that, we want to try to address the uremic crisis, the electrolyte disturbances, and making the patient as stable as we want, and we want to kind of bring fluid. Therapy to restore the intravascular volume if the patient is dehydrated and we want to make sure that we don't overdo it because there are complications associated with associated with overhydration.

So we want to prevent ischemia, making sure that we have a good, vascular replenishment. We want to avoid hypertension, we want to avoid hypertension as well, but we also want to avoid over hydration. And in order to succeed with that, we need to do judicious fluid therapy and that means that we need to precisely calculate the need of the patient using the sum of the maintenance fluids plus the deficits that we calculated from the dehydration of the patient, plus the ongoing losses of that patient.

And you have to remember that the cat is a small being, so every drop of fluid is important. Sorry, which means that. Water that is given through anal nutrition, any dilution of medications, any CRIs, any flush will eventually represent an important volume for this patient because if you have an oligoanuric patient or an aneuric patient, you don't want to push them into overhydration and every millilitre will count.

This is a nice diagram from a review paper from Kathy Langstone. It's a dog, not a cat, I, I know. However, it's the same, issues that we will encounter with our, feline patient if they are, overhydrated.

So we really want that judicious fluid therapy, very precise calculation of fluids for this patient, to try to avoid as much as possible fluid overload and overhydration. Because if you have very, suffering kidneys, the renal excretion of water will be impaired and you are gonna have water retention because your sodium is not excreted as well as it should be and therefore For that will cause edoema in all tissues, including the kidneys themselves. So sometimes you, you see an azotemic patient, you put them on fluids and then the azotemia worsens.

That's probably because there is edoema in the kidneys and it's just worsening the picture for the patient. In cats, the first place that we are gonna see, evidence of overhydration is gonna be the lungs, probably. Moreover, if there is any other cause of inflammation in that patient.

So monitoring the respiratory rate is very important. Monitoring the weight of the patient is an easy way to have a surrogate for hydration and fluid retention or not. So you want to assess the hydration of your patient, and that's mandatory.

It's something that you do every day when you do a physical examination. And as I mentioned, the weight is a good surrogate of hydration. In hospital, it's easy to monitor the weight.

So these patients with AKI regardless of the cause of the AKI should be probably weighed every 4 to 6 hours in the initial states when you try to rehydrate them, just to make sure that they don't gain more weight than what you think they need. So if you think your patient is 10% dehydrated, that means that he should gain 10% of his weight in fluid to be rehydrated and then he should not go above that when you keep weighing him throughout the day. Then you want to measure the patient's urinary output if you can.

Again, some reminders here that polyuria is an increased urine production with more than 2 mL per kg per hour for your patient. A normal urine output is between 1 and 2. Relative olliuria, which is a patient on fluid that is not urinating as much as you would like, is a patient that is on fluid and urinating less than 2 mL per kg per hour.

And then oliura and anuria are states where the urine production decreases or stops, so your patients are going to produce less than 1 mL per kg per hour, or virtually nothing, which we define as less than 0.25 mL per kg per hour. It's not always easy to measure the urinary output when we are talking about a cat, you obviously cannot, you know, collect the urine and measure the volume that they've urinated.

So you would have to place a urinary catheter, which is not always either easy or indicated, or you have to find, ways to do, to do that, with a surrogate. You have to assess the ongoing losses of your patient. Is your patient vomiting?

Is your patient having diarrhoea, which both are gonna lead to loss of fluid of some sort, and then urinary losses, is there a urine production, is there polyuria, is your patient incontinent? Again, to measure some of these losses, you can place an ending in a catheter, but the weight is probably what is the, the most practical I find, regardless of the, the, the setup in which you're working a big hospital or a smaller hospital, you all have scales and, waiting a cat is not the most challenging thing to do. And then once you have assessed your hydration, your Ongoing losses, you're gonna adjust your fluid rate based on that.

And you're gonna include the, the sensible loss, as well, which usually are considered to be 0.25 mL per kg per per hour, for, for, for a cat. If you forget this one, it's probably all right.

You will have still a good assessment of the, of the, the needs that your, your patient has for his, for his fluids. And, and that will give you the formula to calculate your replacement fluid, the maintenance, the ongoing losses, the insensible losses, and then you might have your dehydration correction. So if we take Yukiko for example, she was 10% dehydrated, so that's your dehydration correction, and then her insens and bloss are .

Are normal because she's a normal, animal. Her ongoing losses, she had none because she was not urinating and she had no GI disturbances when she was presented to us. And then she had, maintenance needs.

So that kind of. Gives you a volume and then you need to distribute that volume over. Usually we try to correct the hydration over 12 hours and then once you remove the the dehydration from the equation, that gives you the volume for the rest of the stay.

Obviously this will be updated and changed if the ongoing losses start to change. So either the patient's gonna start urinating more or having GI troubles, you will kind of revisit and correct your formula. And you want to measure the in and out again, using the weight as much as possible, probably for a cat.

If they are very critical, maybe every 2 hours, if they are more stable, maybe every 4 hours will depend a little bit on on the stability of your patient. But it's important to realise that the kind of preconceived notion that a high fluid rate and force the recess is mandatory for animals with the AKI is probably wrong and . If there is any suspicion for oligua or relative oligua, you might actually make things much worse, much weaker, and have a patient decompensate when you were thinking you were doing something kind of life saving for your patient.

When do we talk about overhydration? So overhydration is when your patient has gained more than 10% in weight compared to its weight on presentation. It's gonna show up with an increased respiratory effort, increased respiratory rate, and the lung sounds are gonna change as well, and you're gonna be able to hear harsh sounds, crackles, that are compatible with pulmonary edoema, and the lungs are really the first place where the cats are gonna show signs of decompensation.

They kind of develop chemosis, so swelling of their eyelids, and, some serious nasal discharge. So very clear kind of watery nasal discharge there. Their skin to will change and, they will feel much more like gelatinous and a bit like kind of like swollen all over.

. And that means that the interstitial and intravascular fluid balance should be revisited because it has to be changed and the patient needs to receive less fluid. So monitoring frequently again, I think I've said it for the past 3 slides now, but it's important to monitor this patient again, if they are close to oligouria maybe every 2 hours, if they are more stable, maybe every 4 to 6 hours. It will also depend on which.

In which settings you're, you're working and, and I can recognise that in, in a general practise, you might not have the, the, the nurses, available to, to, to weigh your patient every 2 hours. In a bigger practise, you might have that option. And that might be a criteria to decide to refer your patient early or to keep it on, to do some more investigation before you make the decision to refer as well.

There is one study in cats with ureteral obstruction that has shown that a fluid overload in the initial stage of hospitalisation was associated with negative outcomes. And I think it makes sense that, you know, if you create edoema in a kidney that was already not functioning very well. Well, it's gonna impair that kidney function even further and so the the recovery is going to be impaired, the ability of the patient to go for an anaesthesia if we need to do a corrective measure, surgical correction for the obstruction is also going to be impaired for that patient.

So I put that diagram here again because I think it's a, it's a very nice sticker and that little quote from Paracelsus that we, we all use in, it's the same translation in French as well. All things are poison, for there is nothing without poisonous qualities. It's only the dose which makes a thing poison.

So even intravenous fluids can be dangerous in this patient and it's important to use them, judiciously. Some adjunctive therapies are recommended for cats with ureteral obstruction, and the goal of these therapies is to try to make the stone move. So the fluids are going to increase the urine production, hopefully, so that's already an increased pressure within the urinary tract to push the stones down.

However, the use of osmotic diuretics such as Manitol has been reported. The goal of manual therapy is to try to increase the urine production, . And to push harder on the stones and the debris through the ureter to try to make them move down towards the bladder.

Mannitol will increase the intravascular volume, and it's only secreted via the kidney. So you need to make sure that your patient is able to process the manitol and urinate, so it's contraindicated in patients that are oligoanuric or aneuric. Sorry, the other drugs that are used are, urethral relaxators, if I may, and they have shown to be very efficient in humans, but there is limited, scientific evidence.

In veterinary medicine, it's more an opinion based use, but I think there are some improvement that I've seen with these drugs. So alpha receptor agonists are antagonists, sorry, are gonna create a relaxation. Of the straight muscle of the ureter, and the, the, the persis of the ureter is gonna be reduced, hoping that Will help the stone moving down.

You can use prazoin, you can use tamsulosin, just monitor the blood pressure of your patients. You, you want to make sure that they are, you know, ideally well hydrated but also normaltensive before you use these drugs. You can use ureteral smooth muscle relaxant, like amitriptyline, glucagon has been reported as well, but I've personally never used it in that, and I would be a bit worried to use glucagon.

But it's been reported in human medicine and in few case reports as well. And then antibiotics are often associated with the initial steps here, either because you've collected a urine sample that you have submitted for a culture already. And there were changes in the ultrasound that are supportive of a urinary tract infection, .

In the retrospective studies that we have about your ritual obstruction in cats, it's associated with infection about 32% of the cases. Mhm. This is a table from a paper in JSAP that I find quite nice.

It's a two-part presentation from Dana Clark from the University of Pennsylvania and that's a listing of the drugs that she recommends, so you can find the processing and the Tamsulosin. Which are my go to personally, I, I would go with these ones, first. I have used Manitol in a few cases.

I have used furosemide in one case, because I wanted to try to challenge the cat and see if I could resolve the auria, and obviously Manitol was contraindicated in that cat, . I've not used amlodipine in that specific . In that specific context, but it would make sense to use it and I think it's been shown in human to help as well.

If you have a patient who would be hypertensive, amlodipine is probably the only drug you can give to treat hypertension, in cats with AKI. So, that would be another indication to go with amlodipine. And finally, you probably want to initiate some pain management as well.

I don't know if any of you have ever had kidney stones, but it it's very, very painful, . Situation and that when there is a partial obstruction from your kidney stone, it's apparently one of the worst pain you can feel. One of my friends has kidney stone and like he is on the floor when he has episodes where, where the, the stones are actually passing.

And in human medicine, the, the first treatment is drink and try to get that stone to pass. I guess the ureters and humans are a bit bigger, so it might be a bit easier for us, but it's a very, very painful, thing. So if you, if you have evidence of stones, at least, I would start, pain management.

If You suspect a stricture and you have a big, big dilation of the kidney, you can imagine that the pressure in that kidney is very high and the cat must be uncomfortable. So depending on the level of, of discomfort, I've used fentanyl as a CRI or buprenorphine, these are probably the two ones that I will use the most in cats with ureteral obstructions. So if we go back to Yukiko, and, and I'm going a bit more fast this time compared to the previous one, but basically, in, in summary, we had an aneuric cat with a major azotemia and the creatinine over 2000.

We had evidence of obstruction in both the radiographs and the ultrasound with the stones in the kidney, the ureter, and the bladder, and the cat had hyperkinemia as well, which makes sense with the auria. So the first step that we did, we started the cat on some fluids. She is the one cat where I was trying to challenge her kidney with fluid boluses and a boluses of furosemide to see if I could.

Get her to produce any urine, but that was not very easy. We confirmed the hyperkalemia as well, using an electrolyte, specific machine, and, and the the potassium was 9, so we initiated an insulin dextrous protocol for her. So you can imagine that that was already a lot of fluid that we were giving to that cat who was a neuric and so there was a worry that we were gonna over .

Overload that cat, so the deal was to try to reduce our potassium to something acceptable and then go to surgery quickly to relieve the obstruction because we have no hope that being bilaterally obstructed, we would be lucky enough to have both kidney . Kind of deobstructed with just medical management, knowing that we could not use manitol and, and we were fairly limited, so really like we managed to stabilise the potassium to make her a better anaesthetic candidate and now the obstruction needs to be relieved. So as we discussed, the medical management is very kind of intuitive.

I'm sure you, you know, you would have thought of all of these drugs if you were asked, with the fluids, the ureteral relaxation, the pain management, trying to increase the diuresis, but the success rate is very low, it's below or around 10%, depending if you are an optimistic or not, and it's been shown to be efficient in stones that are very distal. I think at this point in, you know, in my career I've, I've seen probably about 25-30 cats that needed to be . Unobstructed, let's say, to not spoil the rest of the presentation, and I've seen among them I've only had one.

That passed the stone into his bladder and just needed to go for a cystoomy a bit later. But all of the others, there was no, no change, if not worsening of the situation and they needed something else. And it's been shown in one of the retrospective studies that only stones in the distal third of the ureter will move and pass down into the bladder.

So now we have to consider surgical options and finding a more invasive way to remove that obstruction and get the kidneys to work again. So how do we do that? The historical technique is the ureterotomy, meaning that we go in, you do laparotomy, you get to the ureter, you open the ureter, you remove the stone that you've previously, previously seen and you close the ureter.

A cat ureter is around 1 millimetre for its outer diameter. So this kind of surgery requires magnification like magnifying glasses, surgical microscopes, not every practise is able to do that, . Because you, you might not have the equipment that is needed for that surgery.

You also need special material, surgical material, like very small, tools and very, very small sutures to be able to access the ureter, but to be able to open it safely, to be able to handle the tissue safely and to be able to close the tissue without creating too much reaction and create a structure right away just from your intervention. Complications are reported in a few retrospective studies and there is about 31% of complications, most of them being leakage of urine in the abdomen and stenosis at the level of the surgery, which results from the inflammation, the edoema that happens postoperatively, and then the fibrosis that will occur around the, the suture material. But there is also a 21% period of mortality and I, I would think that probably this is a bit biassed because.

It's a, it's a technique that is less and less favoured over the past year. So these studies are a bit older, maybe we, we are a bit better at diagnosing these cats and going to surgery faster so they might have a better Renal function and be a bit more stable for the anaesthesia. And, and I think we might have progressed as well in terms of post-op care and, and maybe even anaesthesia, options.

But still quite a high period of mortality for this, for this patient and a, a decent amount of complication with one third of the patient having like immediate complication due to the surgery. So a bit more recently and, and still ongoing in some practises, the use of stent has been developed and has been described in feline case theories and feline case reports for urethral obstruction. Stents have the beauty of being temporary or permanent, in humans it's almost always temporary because they, they try to have the implants out of the patient to prevent further complication like infections.

In veterinary medicine it's a bit more variable depending on the patient to clinician. And the underlying cause as well. But at least you know that there is an option to remove it.

If you're worried about infection of the implant, if there is pain associated with the implant with inhuman is something that is quite commonly reported with people that have stents. For cats, obviously, you need to buy felines specific ureteral stents, because of the size of their ureter. The placement has been shown to be actually challenging and difficult, and it's something that we do routinely in dogs, but that is kind of falling out of favours in cats just because the, the ureters are so narrow and the peristalsis seems to be very strong and even maybe stronger when you have some sort of obstruction and inflammation already ongoing.

That there have been a lot of reports of, of failure to place the stent, in, in, in cats. When in dogs, it's usually a fairly, Not routine, but it's something that is done a bit more commonly and seems to be more accessible in terms of, of feasibility. So the complications associated with the stent are the difficulty of the access.

So there have been described, . Retrograde technique from the bladder up to the kidney and antegra technique from the kidney down to the bladder. This later seems to be the easiest, however, Still challenging and the access to the, to the PLA cavity might be difficult.

On the right, you can see an intrahop picture via a fluoroscopy. So you can imagine that the patient is like draped and they are in surgery with, with the patient and they have this kind of. It's called the CAM, so it's a, it's a C shaped retrograph machine basically that does fluoroscopy and live X-ray recording.

So you can see how you are when you place the the catheter in the cale pull of the kidney. You can inject contrast like you have on that image, so you can visualise here the pelvis and the calluses of the, the kidney and then that's the proximal ureter that is very dilated and then tapers down here. So there must be a stone, a stretcher or something.

I, I don't know what was the, the diagnosis for this patient. And then through that incision, you're going to place a guide wire and try to enter the ureter and then try to place the guides down to the bladder and then place the stent and then close that little opening here. In a lot of cases, this is not feasible, so they have to open here the, the pelvic cavity, which increases the risks of leakage and complication.

Sometimes they have to open the bladder and kind of open the papilla to let the stent pass through. So it ends up becoming quite invasive in terms of surgical approach. Other complications that have been reported are a rupture of the ureter.

You can imagine that when you push your stent down and here you have like a kink or whatever stricture, this might rupture if you force on it too, too much, and then leakage in your abdomen, either from the incision site or from the ruptured ureter. Overall survival time reported with stents, again, older studies but still I think relevant, 500 to 750 days roughly. So, you know, over a year and that's the median survival time, so it means that 50% did better than that, but, we are, we are like, yeah, around 2 years, 2.5 for, for the stent, survival.

In terms of long term complications, stents can re-obstruct, because they can become encrusted or they can have stones that go through the fenestration and just obstruct them. They can migrate, so in the picture here, you can see the stent completely crawled down into the bladder. There actually might be two stents or it's a very long one.

But it's no longer doing its job because it's not going from the kidney to the bladder. It's just like all into the bladder. They can also sometimes go up, a bit more common in dogs, but feasible in cats as well, go up and crawl up into the pelvis if the pelvis was initially very, very dilated, for example.

They can become infected, they can create chronic, Inflammation, urethritis. This is an encrusted stent. It's not the most impressive I've seen.

I've seen one that was like entirely covered of crystals, which is kind of beautiful but also a bit scary. But this encrustation can promote, biofilm or can obstruct the little fenestrations that you see here and there, and prevent the urine flow to be good and, continuous from the kidney to the bladder. And in one of the retrospective study, they, they showed that they had to replace the stent in 27% of the cats.

Which is not nothing, and if you had a UTI at the time of stent placement, that was a negative prognostic indicator in terms of survival and in terms of stent replacement. And if you had a proximal obstruction, that was also a negative, prognostic indicator in terms of, success, for the initial surgery. So the, the very high up on the ureter structure, and obstructions were more difficult to treat than the distal ones.

You have something, if I go back to the previous one, you have something that's also kind of rolled up inside your bladder. So that has also been associated with long-term complications such as chronic lower urinary tract disease with cats that are straining or having hematuria, and that's about 10% of the patients. And then the most recent development has been the development of this subcutaneous urethral bypass.

And that's a dual, device composed of a locking loop nephrostomy catheter and a multi-fenestrated cystoomy catheter that is attached through this port where you have a multi-punctional, like you can puncture that. Membrane here multiple times and inside the little metal port is a chamber where the urine flows, but using a specific needle, a Uber needle, you can access that chamber and sample or inject, sample the urine or inject fluids into the system. The first goal being to check for patency, obviously.

The, so the device, one of the catheters goes into the kidney, one of the catheters goes into the bladder, and then this is placed subcutaneously, usually on the ventral abdomen, sometimes a little bit laterally depending on the surgeon, to be accessible easily for for sampling. That's the, the, the kind of promotional picture on the website of Norfolk, which is the company that commercialised the subs and that you can order them from, so you can see it's a fluoroscopy image, that's why it's not exactly like a radiograph, but you can see the nephrostomy catheter here that is looped into the pelvis. The loop prevents the, the traction and the, the, the movement as much as possible of the catheter down into the ureter.

And you can see that catheter is attached to chamber here that is subcutaneous on the ventral aspect of the patient, and then the second catheter here is coming and looping into the bladder. Here there is a little dacron that is actually glued and or sutured to the renal capsule to prevent leakage and to prevent motion of the catheter and here there is usually another one that is attached with a purse string to the apical pole of the bladder here. Sorry, to prevent again leakage, and these two dacrons are allowing for replacement of the tubes if needed, so you can remove just the catheter and replace it using the same entry point for both the nephrostomy one and the cystoomy one.

So it's still the surgery you need to do a ventral midline laparotomy. I, I am an internist, so I don't perform the surgery myself, but I have scrubbed into some of them to help surgeons who are not familiar with it. It's sometimes nice to be both of us, where I work at the minute, the surgeons do them all by themselves.

So you need to do a ventral midline laparotomy. You need to isolate the caudal pull of the kidney. This is where you're gonna insert like a, an 18 gauge catheter and then pass guide wire, and then Place your catheter over the guide wire, remove your guide wire, and then curl your catheter within the, within the pelvis.

For cats with minimal pelvic dilation, and again, I, I would refer to part one about that discussion. You can have obstruction and yet the pelvis doesn't dilate as much as you would think. You can advance the catheter further into the proximal ureter and curl it into the ureter because you will have more room than the pelvis.

This has to be done under imaging control, and the gold standard for that is fluoroscopy, which is the images that I've presented until now. However, there are more and more practises that will place the subs, using ultrasound and basically they do pair operative ultrasound using like a sterile . Sleeve to cover the machine and you use ultrasound and what you want to see is you want to be able to see when you inject in the catheter that you are within the pelvis and or the ureters.

So the fluoroscopy is the gold standard. It's the most common one. It allows to do an antegrade pyoureterogram, which will be the gold standard to confirm the obstruction.

Again, the US, the, well, ultrasound and radiographs are not 100% sensitive and specific, but an integrated pyloureterogram using contrast is, so if you have a fluoroscopy machine, you confirm the obstruction and you're like, OK, it's obstructed, I am placing the device. There is 1, there are actually 2 now, 2 retrospective studies with ultrasound. And they have shown that they don't have more complication, than the fluoroscopy one, and they have good survival time.

So that's the first one, it's a French one, and that has been published in 2017, and I have a little summary of the other one a bit further down the presentation as well. But they have good survival time, and no major complications, so you can really use your ultrasound machine to place subs, if you are a skilled enough imager. Complications that are reported in the different studies are leakage, bleeding because obviously to place it, you have to go through the renal parenchyma and it, it is a very vascular organ.

So bleedings have been reported haemorrhage and even obstruction of the newly placed device by a blood clot have been reported in the literature. I've had. One like that who replaced the, the sub and the cat obstructed like right away overnight, because of, of, of a clot.

There are some case reports where people have injected fibrinolytic agent like TPA in the, in the port. I, I haven't, unfortunately, the owner elected to, to euthanize the cat. Not an ideal situation if you have a major bleed.

There are some suspicion based on human medicine that You might have dysfunctional, platelets because of the severity of the azotemia. So in some places they, they do give cats DDAVP or vasopressin before the surgery to try to improve platelet function as much as possible before performing the surgery. In terms of long-term outcome, you can see that it's, it's not perfect, .

And none of the three techniques that we have discussed so far are perfect, that subs will probably reocclude in 25% of them. Sorry, either because of mineral accumulation or infection and biofilm. And there is one retrospective study where they reported a 13% rate for exchange.

As I said, you can change just the catheter, you don't have to redo the whole kind of, placement. You can use the same openings that you've, you've made the first time. And these cats are prone to have chronic infection.

You have a permanent implant and, there are risks of infection and, Biofilm growing along the the pipes of the subs. So to serve or not to serve is always for me the question and what is the decision making process that I have. There are no guidelines that are available because it's a fairly recent, device.

There are more and more studies that are published and I'm sure like we will probably try to compare all the technique and see if there are situations that are better than others. Right now it's really. Left to clinician preferences, availability of a surgeon able to place that or an internist able to place them, willingness of the owners to follow up with what is needed when you have a permanent implant.

I do have a personal bias towards subs, and I think it's a common trend at the moment, among specialists and re hospital to place more and more of these because. If you know how to place them and if you have the equipment, it is not necessarily a very long surgery, it's a bit delicate but it's not overly difficult and I think the complication rate are Not better in in publications but maybe a bit better in in practise than than ureterotomies and definitely placing stent could take forever because some of them they are just never able to advance them in the ureters. But again, the, the first part of the decision making is to implement medical management for 24, 48 hours.

Personally, that's what I would do. I would not push it to 72 with very close monitoring to see if there is any chance that this stone is gonna move. It gives you time to stabilise your patient.

If we, if we go back to Yukiko, it gives, gives us time to treat the hyperkalemia and perform the imaging to confirm the obstruction. And then it's very important to have a discussion with the owners about the interventions that are available and the risks. I think it's, it's fair to discuss about bleeding.

They could obstruct subs and even stent, but with stent, you don't really go through parenchyma, because, well, unless you go through the, the, the first opening that you do in the kidney, but most of the time they have to do a pilotomy to place the stent. You have recurrence, and we've seen that it's around 25% that this, devices will be obstructed, or if you do a surgery, it's about 25, 27% that the ureter is going to structure and re-obstruct. And obviously, if you have nephrolithiasis, regardless of the technique that you decided to use, if one of these nephros decides to move and goes down to the ureter or goes down the sub, there are risks of obstruction.

I will just have a little caveat there in the sense that the. The fenestration in the sub catheter or the stent are very small, so I would think if you have a big nephrolith, it's less likely to obstruct compared to a previous ureterotomy site, but that is what is published in the literature at the moment. The sub is permanent and to my knowledge, there is only one place where they remove them and it's the Robert College.

So in some cats it's been shown that once you've relieved the obstruction, the cats might be able to re-canalyze their ureter and have a ureteral flow again. And I know that the RVC has removed some subs in cats where the tub was creating issues and they were confident enough that there was enough, ability of the urine to go down the ureter again that they would be safe to remove it. I have never removed a sub.

I've replaced some, but I've never removed one personally. Structures are a risk if you're using ureterotomy or if you're using a stent and you have to remove the stent if it was really creating a lot of inflammation, there are chances that the patient might have a structure in the future. And then technical issues might happen with all modalities.

Either you don't have the equipment, the equipment is too far, and, and you can't do that. But I think for some, for most of, of these procedures, referral is needed anyway, to have, access to an ICU for the postoperative period, for these patients. And then it's important to know how to manage your post obstructive diuresis because these cats might have a massive diuresis afterwards and need to be like a lot of fluid, but that means that they need to have a lot of monitoring as well.

What if my patient has an infection? Like if I, if I know or highly suspect that the patient has a UTI or well an infection secondary to the stone or or whatever, well, stents are temporary and, and, and are attractive because they are easily, well, relatively easily exchangeable, . They are intraluminal, there, there is no implant kind of consideration like a sub that is a permanent implant, to me.

Subs are exchangeable if you think that there are biofilm growing within the, within the. Like kind of the piping of, of the device, but obviously placing them in a patient with already an infection, a bacterial infection, makes that patient more at risk to have chronic infections. And then if you have a very proximal stenosis or obstruction, so very close to the elic cavity to the junction between the kidney and the ureter, surgery is very difficult and if, if it restructured there, then you, you've gained nothing.

Reimplantation is impossible, so you can't even shorten the length of the urethra to reimplant it. So. A sub might be ideal for these patients because again stents are challenging to place and if it's really narrow stents are gonna be even more difficult to place.

So if we go back to Yukiko, we, we went and placed a sub. She, she went that night once the potassium was a bit more stable because she was auric again and you can see that her creatinine responded beautifully to the relief of the obstruction and our renal function improved, . Right away, she had a massive, massive post obstructive dialysis.

I'm sure some of you have seen that with like cats with urethral obstructions and You place your urinary cat and the cat just urinates all the time and you have to place cats on like massive, massive fluid rates that you've never even reached for dogs. Yukiko was on like something stupid like 36 mL per kg per hour at some point, like just to keep up with her fluid losses. And then you have to balance that and try to reduce and challenge the kidney to be able to concentrate the urine again and retain the fluids.

But this patient needs a lot of monitoring post surgery. In the immediate perioperative period, anaemia has been one of the main issues that has been described with cats are having a sub placed again, the, the, the renal parchema is quite vascularized, so they can bleed quite a lot, and some cats have knee transfusion to either get through surgery or the post-operative period. The post-obstructive diuresis has to be managed and it's important to, you know, make sure that you keep up with the fluids.

Overhydration is bad when, when they arrive in AKI but dehydration because you can't keep up with the fluid is also bad and will damage the kidney function. You want to control the pain, like they were painful before, they have now an implant, so there is some pain management that needs to be done for a few days at the very least. And then they do have perioperative antibiotics, you know, it was an open surgery, went to the kidney, maybe it was infected.

Usually we submit urine from the bladder, but we also submit neurine from the kidney for culture. But at the very least, they will have a few days of antibiotic like any other open abdominal surgery. And then another important point is feedings.

It's important to feed these cats quickly. Often they have not been eating very well before for a few days, and you don't want them to have, hepatic lipidosis on top of everything else, you know, like they already have quite a big expensive bill. So, probably want to avoid one more problem.

You, you, it would probably be very damaging as well and, and quite. Increasing the morbidity of, of the problem if, if these cats were not able to, to be fed appropriately. So in a lot of places, when we place subs, we place a feeding tube at the same time just to make sure that we can keep up with the calories.

It also helps to keep up with the water and some of them that needs to receive water, for a bit longer. So often I will discuss with the owners, that we will place an esophagostomy tube at the time of surgery. Some other places prefer nasal gastric tubes to start with, whichever, but I think it's, it's important to include the feeding in, in the, the immediate post-op, post-op care.

And finally, they need to be regularly seen to make sure that the device remains patent and that they are stable, that the the the sub has not dislodged or or done anything funky. So we assess the patency using a human needle and that's very important. It's, it's a needle with a very specific shape and a specific curve, which allows for that membrane that I showed you on the, on the device to be used like, I don't remember, I think it's like up to 400 times.

If you use a straight needle, you're going to perforate it and then it's gonna leak. And then you're gonna have urine going on the subcut. So these cats with a sub should not be checked with like regular random needles.

You need to have the equipment if you are meant to do the follow-up, or the patient has to go back to the practise where they were placed to do this part of the follow-up at least. And it's an ultrasound guided test in the sense that you will inject some fluid in the system and you want to see bubbles in the, in the renal pelvis and in the bladder to make sure. That the patency is, is good both ways.

Usually, we do it prior to discharge after the surgery, then 1 month goes up, and then we do it every 3 to 4 months. Like, chronic kidney disease staging. Sometimes more often if we think, like, we might see the patient more often if, if the CK.

Warrants more rechecks, but we will, we will check the patency every, every 3 to 4 months. Usually that is associated with the full CKD staging, so we do bloods, we do a urinalysis, we do a blood pressure, and we do a urine culture. Urine for this patient is always, always obtained from the chamber, and we do not perform cystocentesis, anymore on this patient after the surgery, because it's too risky to get your, your needle stuck in the, in the catheter that is in the bladder.

So you have an access that is subcutaneous, much more safe, and as long as you have the right needle, you can, you can obtain urine very easily from them. Infections, that's the reality, and, and there have been a few recent studies that have been published showing a rate of infection of 25 to 35%, that are considered chronic UTIs because they are associated with clinical signs. E.

Coli has been shown to be the most common bacteria. If the device has been placed in a patient with a pre-op UTI, about half of them will be able to get rid of the infection, but the other half, will, will have chronic UTIs. Patients with a negative urine culture at the time of the surgery can develop infection and are included in this 25 to 37 to 35%, because it's rare that they are actually infected beforehand.

I had one cat where, I mean, given the ultrasound, we, we knew it was gonna be pus, and when we placed the sub, it was literally pus coming out of the kidneys. And yeah, she had chronic reinfection. The interesting part was that it was never the initial bacteria that came back, but somewhat, she, she got, yeah, chronic reinfection and the owner was Not the most diligent owner and would not come for all of the, you know, 3 to 4 month recheck, but she was really good at picking up when the cat was clinical from his infection, and, and she was always right, and it was always growing.

So it's been shown that if you have pre-operative UTI, you might stay longer in hospital because you might have a bit more time to recover, from your pyelonephritis, that also participate into your AKI. And you might have long term positive urine cultures as well, . More recently, and, and that was not available when, when I, I saw that patient, with the pus coming out of the kidneys.

We are using Trice EDTI as a locking solution. So it's a product that has been developed, and it's commercialised by Norfolk in. In most of, the country, so in the UK for sure, we, we have it from Norfolk in Ireland as well and in the US.

It's a bit more tricky to get in Canada, but they, they found another company that, that, sells through CDTA. Basically, it's, it's similar EDTA to the one that we use as an anti coagulant, . And we, we have added it as now the, the final step of the protocol when we flush the subs.

And basically we use it as a locking solution. So we inject it in the device and we do not reaspirate it or we do not rinse it so that it sits in the tubes for as long as possible. It's been shown to prevent bioin formation, and it's been shown to prevent encrustations of the the subs, and so to decrease a little bit the need to replace subs in some of our patients.

And they also have developed a protocol with daily infusion for some patients with chronic UTIs that don't respond to, antibiotic therapy because we think that there is a biofilm that makes the, the the actual bacterias much more difficult to reach with the concentration of antibiotics that we have in the urine that circulate through the system. So it, it, it's fairly recent, but I think it's gonna help making subs, a bit less of a headache for some owners and some vets in terms of like infection and obstructions and, and what to do with them, long term wise. And so that's the most recent retrospective study that has been published in the Journal of Feline Medicine and Surgery.

They've shown an amazing 4.5 year, 4.25 year, median survival time, which means that half of their patients have lived over that, and.

They, they, they did not use fluoroscopy as well for any of these patients. They used, ultrasound, so basically they, they, they showed that ultrasound is safe and has, as good outcomes as the fluoroscopic placement, which is good because it shows that places with no fluoroscopy can still, can still place subs and, and help these cats with ureteral obstructions. So in conclusion, again, going over both the first and the second talk, ureteral obstruction is a, is a, is a challenging diagnosis, and I think we see more and more of them, not because they are more and more common, but probably because we are better at diagnosing them.

Remember that the, the common, radiographic tools that we have, radiographs and ultrasounds are not perfect, but almost perfect, 90% if you combine both to diagnose obstruction. The most common one being secondary to stones, but you can diagnose obstruction based on the presumptive clinical diagnosis if you have a good concomitant suspicion from the presentation, the clinical pathological data, and the imaging findings, even if you don't see the stone, it might still be obstructed or if you don't have a massive pedic dilation, it might still be obstructed. Time is nephrons and we will lose a lot of renal function very quickly if you don't relieve the obstruction.

And as you can see on the right side of that slide, it's a study that has been conducted at the University of Montreal and that is under revision at the moment, but the three centres which are Montreal on the left, the AMC New York in the middle, and University Davis, California on the right. I've shown a major improvement in creatinine, post decompression, so it's important to treat this, this patient quickly to, to help and improve and restore the kidney function as quickly and as, as well as we can. Medical management is necessary to stabilise your patient, but it is limited in terms of, success of outcome, and it's unlikely to resolve the obstruction if we are realistic because it's going to be less than 10% of the cases that will respond to medical management alone.

So judicious use of your fluids do not overload your patient and then use of rosemide or manitol to try to push these stones down, use ofrazin, damssulosin. Maybe amitriptyline if you want to try to relax the ureter and help, the compliance of the ureter for the stone to pass and and go down into the bladder. But most likely you're gonna need to do the compression.

I think the subs are becoming the new standard of care because they are easy to place and it's been shown now that you don't need fancy fluoroscopy to place them, but just an ultrasound. They have a very good long term survival in that very recent retrospective study. And then they just need to be managed like a long term chronic kidney disease patient plus or minus the UTIs.

And to finally conclude the, the talk, this is er, he's one of the patients that we have here in Dublin, and I just saw him last week. We placed this, over a year ago now, like close to a year and a half ago. As you can see, his creatinine after 1 month's, post sub was back to completely normal with the creatinine of 149 millimole per litre.

And he's been doing well. He had a kink and a massive, encrustation of his subs. So we replaced the device six months ago now.

And, unfortunately, his renal disease is slowly progressing and he is now at stage 2. Aemic chronic kidney disease, but he's doing well and he still doesn't have an infection, so I'm actually quite happy with that, knowing that he had the procedure done twice because we had to replace the stents. So thank you very much for, bearing with me, for the past hour.

It's, it's starting to be a bit late, but I would be very happy to answer any question you have. And, if you don't get to, to ask me questions tonight, or if you, if you watch the, the, the replay of the, of the webinar, feel free to email me if you, if you have anything that, you wonder about. Thank you.

Thanks, Beno. That was absolutely fascinating and yeah, it's it's incredible the way medicine has improved and developed and I can remember when they first started with the subs and it was as if it was an alien spaceship procedure, and now it's been placed with ultrasounds and no sea arms. It's incredible.

Yeah, no, it's, it's, it's nice that it's becoming more available. I think fluoroscopy is not widely available, and, and even big centres sometimes don't have it because the use of it is still limited. So I think it's nice that we can see other ways to place them.

Yeah, that's fantastic. But no, we don't have any questions tonight. I think, everybody is sitting, just trying to take in all this fantastic information you've given us.

So as you said, your email address is there if people want to email you afterwards of thoughts that they've had or when they watch the recordings. It's my privilege to once again thank you for both part one and part two and for your time in, in coming to talk to us. Thank you, Beno.

Thank you very much. Have a good night. Folks, that's it from my side.

Thank you all for attending and I trust you enjoyed it. Remember the recording will be up in the next, 36 hours or so and, yeah, to Kyle, my controller in the background, thank you for all your help and from myself, Bruce Stevenson, it's good night everyone.