25 | Q&A: How to nurse renal and urinary patients with confidence

PodcastUrinaryRenal
Written By Laura Jones

Today, I’m rounding off our renal and urinary series by answering your questions about nursing these patients!

 

If you want to know more about the practical skills we can perform with these patients, dive into interpreting tests in more detail, or want hands-on tips for managing things like urinary catheters, you’ll find it all in this episode!

If you have a question you’d like answered on our next Q&A episode, head to the pinned post on my Instagram and post it in the comments!

Today, we’ve got a great mix of questions about renal and urinary patients, starting with Jordyn, who asked how to interpret urine specific gravity or USG.

Let’s talk about specific gravity

USG is defined as the density of urine compared to pure water. It’s a measure of the solute concentration in the urine, and we know that patients with chronic kidney disease will have a lower USG as the kidneys lose their ability to concentrate urine over time.

What’s normal?

Pure water has a specific gravity of 1.000. Urine specific gravity can range from 1.001 to >1.075 in dogs and 1.001 to >1.085 in cats. However, most fall within 1.015-1.045 in dogs and 1.035-1.060 in cats.

It’s important to remember that USG is relative to things like hydration status, and urine concentration can change significantly over time, with 2-3 x variation in USG reported.

So technically, any USG value could be considered ‘normal’ depending on the patient’s hydration status and other factors.

Concentrated urine

Urine is described as concentrated if the USG is above 1.030 in dogs or 1.035 in cats. This indicates that the nephrons have significantly modified the glomerular filtrate in the process of forming urine, reabsorbing solutes to concentrate it.

Suppose your patient is azotaemic but has concentrated urine. In that case, this may indicate that the azotaemia is pre-renal in origin—i.e., it’s due to poor renal blood flow rather than a problem with the kidneys themselves.

It may also be seen in early-stage CKD patients because we don’t see USG drop until around two-thirds of the nephrons have stopped functioning normally.

Very concentrated urine—and by this, I mean over 1.050—is associated with reduced renal perfusion, but it can also be seen in healthy cats on a dry diet who aren’t drinking much water.

Moderately concentrated urine

Urine is described as moderately concentrated if the USG ranges from 1.013 to the start of the concentrated range. These patients usually have adequate renal function, but may have some kidney disease or another condition affecting their ability to retain water.

Isosthenuria

Isosthenuria is defined as a USG between 1.008 and 1.012. 

This is occasionally seen in healthy patients, but if your patient has azotaemia and is dehydrated, kidney disease and impaired renal concentrating ability should be suspected. 

In an isosthenuric patient, the kidney can neither concentrate nor dilute the urine, causing a consistently low USG.

Hyposthenuria

Dilute urine or hyposthenuria is a USG below 1.008. A hyposthenuric patient can dilute their urine but not concentrate it.

This is usually seen in patients with diabetes insipidus - either because they’re not producing antidiuretic hormone (central DI), or their kidneys can’t respond to that ADH appropriately (nephrogenic DI).

Inappropriate USGs

We must always interpret USG in line with the patient’s fluid balance. Urine may be inappropriately diluted or inappropriately concentrated relative to the patient’s fluid balance. 

Inappropriately concentrated urine is unusual, but inappropriately dilute urine can be seen in renal disease, where the patient is dehydrated but has a USG <1.030 in dogs or 1.035 in cats. 

We do know that certain medications can also cause this, for example, diuretics and steroids. And actually, certain diseases can also do this - including liver failure and pyelonephritis.

Moving on to blocked bladder cats…

We had two questions come up on blocked bladder cats. The first is from Catherine, who asks if we can unblock obstructed cats under Schedule 3.

So, can we unblock cats in the UK?

Now, this is a difficult one, and unfortunately, there’s not one clear answer. The first thing I want to say is that the legal guidance and recommendations will change depending on where you are in the world.

Cat is in the UK, so what she (and I, and the rest of the UK nurses) can do is governed by the RCVS and Schedule 3 of the Veterinary Surgeon’s Act. My take on this will be specific to UK nurses - if you’re practising elsewhere, check with your local licensing authority. And let me know on Instagram whether you can do this because I’d love to know!

So, let’s look at what we can do in the UK. Firstly, we must be mindful that we’re not diagnosing a blocked bladder - because we can’t do that. Legally, we can place a urinary catheter under veterinary direction.

So, whilst we can catheterise these patients, we need to have a patient who:

  1. Is under the care of the vet

  2. Has already been diagnosed with a urinary obstruction (and we know what’s caused that obstruction)

  3. Has a clear plan for how the obstruction will be relieved (e.g. will we need to do retrograde urohydropulsion?)

  4. Is low risk for urethral rupture or tearing

We act as the vet’s practical technicians, performing this skill on their behalf in a patient they’ve already diagnosed. It’s essential we’re acting under their direction and that we’re competent at performing the skill. If it’s a tricky catheterisation or you don’t feel completely comfortable, it’s best to pass this one on to the veterinary surgeon.

And, of course, there is a lot of ‘grey area’ in the literature surrounding what we can do, so the safest thing to do with specific skills like this is to double-check with the RCVS directly.

What about when we anaesthetise blocked patients?

My next question is from a student who has to write an assignment on blocked bladder patients and wants to know more about their anaesthesia considerations.

Of course, this will depend on how your patient presents to the clinic, how long their obstruction has been in place, their fluid and electrolyte balance, and the degree of kidney dysfunction… I could go on. But my general considerations for anaesthetising a blocked patient would be:

  • Fluid balance

  • Electrolyte balance

  • Pain

  • Renal function

You’ll know how significant these factors are on your initial triage examination and emergency bloods. Still, in general, we know our patients often present with marked fluid and electrolyte changes, are usually painful and are at risk for a post-renal AKI.

So before you anaesthetise them, we need to correct any hypovolaemia present and restore circulating volume, correct any hyperkalaemia that’s present, administer appropriate analgesia (no NSAIDs for now!) and consider their renal function.

If your patient is showing signs of AKI, think about the drugs you’ll use to anaesthetise them and measure their blood pressure carefully.

The last thing we want is hypotension, which could decrease renal blood flow and worsen azotaemia. We either avoid alpha-2s or give a microdose of dexmedetomidine to minimise the cardiovascular effects. We’re usually reaching for a combination of opioid and benzodiazepine, with something like ketamine or alfaxalone, depending on the individual patient.

And continuing our chatter on urinary catheters…

We had quite a few questions about placing and managing urinary catheters. First up, Rachel asked what I would do if I had placed an indwelling catheter but did not have access to a closed collection system.

Let’s talk collection system alternatives

This is a great question, and I think it’s something many people face in GP clinics. The first thing I’d say is that the systems are inexpensive, so it’s worth keeping 1-2 in and storing them with your catheters if possible.

If finances are a limiting factor, you can always increase the cost of your urinary catheterisation fee by a couple of pounds to cover the closed collection system—that way, the clinic isn’t out of pocket.

But suppose you’ve just unblocked a patient and you don’t have one - what can you do? You’ve got two options:

  1. Aseptically bung the catheter with a needle-free port and manually empty the bladder every 4-6 hours or

  2. Take a drip bag and giving set, aseptically prepare it, and then empty the bag and line of fluid. Attach this to the urinary catheter and turn it on, and hey presto - your homemade urine collection system!

Just remember, if you are bunging the catheter, you’ll not have continual bladder emptying. You’ll need to ensure that the bladder is drained regularly to prevent overdistension and that the catheter and bung are handled aseptically to prevent infection—because every time you attach a syringe, you risk introducing contamination into the catheter.

This method is also not recommended for overflow or dysuria patients who have bladder atony—their bladders need to stay small while we try to get that urinary muscle functioning appropriately again. 

What about if they’re tangling themselves up constantly?

Jen asks how to prevent urinary patients from continually tangling themselves with their collection system.

This is a really common problem, especially if they decide to start knitting their collection system and fluid line together!

Whilst untangling is OK, it often doesn’t last long. So, what other options are there?

Well, the answer is, unfortunately, not many! You can buy spinning connectors that sit between the urinary catheter and collection system, which help prevent tangling when the patient circles… but otherwise, we’re back to aseptically bunging and then manually draining that catheter.

What I wouldn’t do in any case is allow the catheter to free drip. This is significantly associated with ascending infection and a hospital-acquired UTI.

If you need to give your patient a break from their lines for a while, I’d consider giving them a break from the IV fluids rather than the urinary collection system—of course, if their hydration status allows. The best thing to do here would be to chat with your vet and check if they’re happy to have a few hours off.

What about securing your catheters?

The last question about catheters was from Hayley, who wanted to know how to best secure her urinary catheters to prevent them from pulling, kinking, or causing discomfort.

I tape mine to the tail in cats, and in dogs, I tend to vetwrap the collection system (loosely) to the hindlimb. When doing this, I consciously leave enough slack on the line for the patient to move freely and allow the catheter to move with them. I use a length of tape to let the catheter dangle around 5cm or so below the tail so it can move.

In dogs, I turn the collection system back on itself (in a U-shape) before vetwrapping it loosely over the metatarsal area so they’re not trailing their system under their paws or along the floor.

So there you have it! Your burning questions on nursing renal and urinary patients answered. I hope you’ve enjoyed the last 14 episodes on renal and urinary disease, they’ve helped you provide better care to your patients and given you some new skills to put into practice.

Did you enjoy this episode? If so, I’d love to hear what you thought - screenshot it and tag me on Instagram (@vetinternalmedicinenursing) so I can give you a shout-out and share it with a colleague who’d find it helpful!

Thanks for learning with me this week, and I’ll see you next time!

References and Further Reading

Laura Jones
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