18 | How to successfully care for cats with ureteral obstructions

PodcastRenalUrinary
Written By Laura Jones

I’ll let you in on a secret - I had absolutely no idea that ureteral obstructions were a thing until I went into referral practice.

 

I’d never seen one - but that quickly changed when my own cat, Nigel, got an obstruction himself.

The truth is, though, that ureteral obstructions are being diagnosed more and more often now than ever, particularly in cats - and there is a LOT we can do as nurses and technicians to support these patients. 

They usually present markedly painful and with post-renal AKI, which can be life-threatening if bilateral obstructions are present and often require intensive treatment and nursing care.

What is a ureteral obstruction?

A Ureteral obstruction, as the name suggests, is where an obstruction occurs in the ureter - unlike the blocked bladder cats we’re used to, who present with urethral obstruction.

Several things can obstruct a patient’s ureter - but the most common cause is ureterolithiasis or ureteral stones, accounting for about 80% of all obstructions. Ureteroliths are particularly common in cats because the feline ureter has an inner diameter of about 0.3-0.4mm, so even the smallest of stones can cause an obstruction. In dogs, however, the ureter can distend more easily with fluid administration and is wider in diameter - meaning that most dogs can pass 2-3mm ureteroliths easily.

Other causes include ureteral strictures and congenital malformations, and it can even be iatrogenic. Iatrogenic obstructions are usually seen in one specific situation - where a female cat’s ureters are accidentally ligated at the time of spaying.

Regardless of the cause, the result is the same for our patient - if they have a complete obstruction, their urine cannot flow from the renal pelvis, through the obstructed ureter and to the urinary bladder. 

The result is post-renal AKI, and if it’s not spotted early, the function of the affected kidney can be reduced by 70-80% within 2 weeks of obstruction. 

Partial obstructions are also possible, and thankfully these have a less marked effect on renal blood flow and GFR.

Like other causes of AKI, if we can remove or bypass the obstruction and restore urine flow and renal filtration, we can reverse the kidney injury. How well the kidney recovers depends on how long the obstruction has been present, how severe it is, and how well the patient’s other kidney is functioning.


So that’s what causes ureteral obstruction - but what signs do we see in our patients?

Well, this really depends on whether the patient has a unilateral or bilateral obstruction and on how well their kidneys are functioning.

Patients with unilateral obstructions may show no or very mild clinical signs, presenting only with mild azotaemia. However, if the renal pelvis or ureter is distended as a result of the obstruction, or the ureterolith moves, the patient will show more obvious signs, including marked abdominal or spinal pain, anorexia and vomiting.

We also see marked clinical signs in patients with bilateral obstructions, since these patients will present in severe anuric AKI, with marked azotaemia and hyperkalaemia (and resultant cardiovascular changes). These patients are often severely lethargic, collapsed and hypothermic.

We’ll also see more severe signs in patients who have pre-existing renal disease in their non-obstructed kidney, since they’ll have a significant decrease in their renal function when the better-functioning kidney becomes obstructed.

On clinical exam, many cats have asymmetrical kidneys, with one smaller, end-stage or non-functional kidney, and one large kidney with hydronephrosis or compensatory hypertrophy. This is known as ‘big kidney-little kidney syndrome’.

How do we diagnose a ureteral obstruction?

Like our other renal patients, our diagnostic approach includes blood and urine tests, and diagnostic imaging.

Biochemistry can range from being completely unremarkable in patients with a unilateral obstruction and a normally-functioning contralateral kidney, all the way through to marked changes consistent with severe CKD or renal injury, including:

  • Increased creatinine

  • Increased BUN

  • Hyperphosphataemia

  • Hyperkalaemia

Haematology may be normal or show anaemia of chronic disease if the patient has a history of chronic kidney disease.

On urine analysis, we often see a decreased USG of less than 1.035, pyuria (white blood cells in the urine), proteinuria, and crystalluria. A culture should be performed in all cases, as pyelonephritis (infection in the kidney) and urinary tract infection are documented in around 30% of cats with ureteral obstructions.

After bloodwork and urine analysis, we’ll need to confirm the presence of an obstruction with diagnostic imaging. Using a combination of radiography and ultrasound is the most sensitive and easily-available method of detecting ureteroliths, though other techniques, such as contrast pyelography and CT are also described.

So you’ve diagnosed your patient - but how will you treat them?

Urgent treatment is indicated to restore as much renal function as possible. Most of these patients will require referral for treatment since advanced surgical management is needed, alongside intensive monitoring and management of the patient’s AKI.

Medical Management

Medical management is described in patients with ureterolithiasis, as long as your patient is not oliguric, anuric, hyperkalaemic or volume overloaded (and not in cases of bilateral obstruction) - but it is associated with poor outcomes, with resolution reported in only 8-13% of cases.

It involves the careful use of fluid therapy, diuretics, smooth muscle relaxants such as prazosin, and analgesia - but is often not performed since surgical intervention carries more favourable outcomes. Where it is used, surgery should be performed if there is no improvement within 24-48 hours.


Surgical Management

A few surgical procedures have been used to manage ureteral obstructions over the years. These include direct ureterotomy to remove the obstruction, ureteral stent placement, and subcutaneous ureteral bypass (SUB) placement.

Ureterotomy carries a high morbidity and mortality rate and carries a risk of ureteral stricture development, so it is generally not performed.

Ureteral stents used to be placed commonly, but have fallen out of favour over the last 10 years. These are fenestrated polyurethane catheters containing a pigtail at each end to secure them in place. The stent dilates the ureter, allowing urine to flow through or around it. However, they are challenging to place, and the pigtail end can cause mechanical irritation within the urinary bladder, increasing the incidence of things like cystitis postoperatively.

The SUB system is now the most commonly-used solution to ureteral obstruction in cats. It is a surgically-placed system that bypasses the obstructed ureter completely, allowing the urine to flow through a system of catheters connected to a subcutaneous port from the renal pelvis to the bladder.

The devices are generally well tolerated, with short surgical and recovery time. However, they do require regular long-term maintenance.


And how will we nurse these patients?

Since most of the ureteral obstruction patients we see will have a SUB placed, we’ll focus on the nursing care of these patients for the rest of this episode. There are two main phases of nursing care - in the immediate postoperative period and then long term.


Acute postoperative care

Postoperatively, these patients require analgesia and supportive care alongside the management of their acute kidney injury. This includes monitoring urine output and matching this with intravenous fluid therapy (post-obstructive diuresis is expected after SUB placement, meaning these patients will lose larger amounts of fluid and electrolytes after the obstruction is relieved). Electrolyte supplementation is also commonly needed, alongside intensive cardiovascular monitoring, wound management, maintenance of IV access, and nutritional support.

The patient must also be handled carefully since the SUB catheters tunnel through the abdominal wall, from the kidney and bladder to the subcutaneous port.


Long-term SUB management

After the patient is discharged, our care does not end. These patients require regular reassessments to evaluate their renal function and maintain the SUB device. SUBs are not without complications, and things like obstruction, mineralisation, infection and displacement or fracture of the device are all reported - so we need to regularly check the patency of the device and collect urine samples from it to check for infection.



So that’s everything you need to know about managing ureteral obstructions as a vet nurse! These patients can be tricky to spot, and even more challenging to manage - but there are also a LOT of nursing skills we can use with them - not just when they are in having surgery and requiring intensive AKI management, but long term too.

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

  1. Wills, S. 2018b. Treating feline ureteral obstruction [Online] InFocus. Available from: https://www.veterinary-practice.com/article/treating-feline-ureteral-obstruction

Laura Jones
Previous

19 | How to give great care to your blocked bladder cats as a vet nurse
Next

17 | How to confidently treat and nurse dogs with leptospirosis