From stones to straining… managing stranguria in dogs and cats
It’s Friday evening consults in the clinic and you get that call.
‘My cat is straining to urinate!’
As well as being a potentially life-threatening emergency if a urinary tract obstruction is present, our stranguria patients require a lot of care from us as veterinary nurses.
From triage examination to diagnostics, to placing and maintaining urinary catheters and making long-term plans to prevent repeat obstruction, our role in the management of these patients is vast.
In this post, I’m going to talk you through four common causes of stranguria we see in our patients and share how these conditions are diagnosed, treated and nursed.
And, if you want to know more about the advice and care we give these patients long term, make sure you’re signed up to the Conquer Your Clinics waitlist - as we’re diving deep into care for these patients as part of the course!
What is stranguria?
Stranguria is the term given to slow, painful urination or straining to pass urine. This differs from dysuria which is difficult, painful urination, and pollakiuria, which is an increase in the frequency of urination. These signs are all caused by disorders of the lower urinary tract.
These signs differ from oliguria and polyuria, which are a reduction in and increase in urine production, respectively, and are caused by disorders of the kidneys.
Anuria is the complete lack of urine production, and again, is caused by disease of the kidney (severe acute kidney injury).
To narrow down our list of possible conditions, and plan how urgently we need to see these patients, we need to determine the nature of the urinary tract signs - and this is why taking a thorough history is vital in these patients! Veterinary nurses are ideally placed to do this, as we can use our unique relationship with our clients to get the right information from them.
Many conditions can cause stranguria - including urinary tract infections, stones, disorders of the prostate, neoplasia, and feline lower urinary tract disease.
Urinary Tract Infections
Urinary tract infections most commonly result from pathogens around the external urethral orifice ascending the urinary tract and into the bladder. These pathogens are most commonly bacteria found on the skin and hair around the external urinary opening, but fungal and viral infections are also possible.
The signs seen will depend on the location of the infection within the urinary tract - for example, infection in the kidney can cause acute kidney injury, whereas infection of the urethra will cause stranguria:
Pyelonephritis: infection of the kidney
Ureteritis: infection of the ureters
Cystitis: infection of the bladder
Urethritis: infection of the urethra
Prostatitis: infection of the prostate gland
Vaginitis: infection of the vagina
Urinary tract infections are more common in female patients than males, as they have shorter urethras, leaving less distance for pathogens to travel. The vagina and vestibule also contain a natural flora of bacteria located very close to the urethra.
In cats, bacterial urinary tract infections are most commonly seen in older patients (>10 years).
Pathogens
Most urinary tract infections are caused by a single organism, with E.coli, Enterobacter, Proteus, Enterococcus, Streptococcus and Staphylococcus species commonly involved.
In some cases, bacteria can adapt to colonise the urinary tract more easily. Such adaptations include:
The development of flagellae or fimbriae allows them to attach to or travel up the urinary tract more easily
The production of urease, an enzyme that breaks down urea and increases the amount of nitrogen available for the bacteria
Antibiotic resistance
If these bacteria can overcome the body’s normal defence mechanisms and colonise the urinary tract, infection results. There are a number of defence mechanisms the body has to avoid urinary tract infection, including:
Concentrated, acidic urine
Urinating normal volumes frequently
Appropriately emptying the bladder after each urination
Antibacterial secretions (known as defensins) within the urinary tract
Risk Factors, Signs and Treatment
Additionally, a number of medical conditions are associated with an increased risk of UTI development. Such conditions include diabetes mellitus (due to glucosuria), chronic kidney disease (due to dilute urine) and hyperadrenocorticism (due to the immunosuppressive effects of the excess steroid levels).
Urinary tract infections can be complicated (occurring in patients with underlying disease predisposing them to infection) or uncomplicated (where no predisposing factors or diseases are present). Clinical signs typically include haematuria, pollakiuria and stranguria. Inappropriate urination, odorous or discoloured urine may be present, and perivulval licking, discolouration and dermatitis may be noted in female dogs.
Treatment is achieved with appropriate antimicrobials after culturing the pathogen(s) present from a sterile urine sample. In patients with complicated UTIs, a prolonged treatment course of at least 406 weeks is often necessary, with multiple antibiotic agents.
Urolithiasis
Urolithiasis is the formation of calculi or stones in the urinary tract (uroliths). These can form in the upper and/or lower urinary tract, including in the kidney (nephroliths).
Formation
Uroliths form when the urine becomes supersaturated with crystalline components or stone-forming substances. They commonly form in the bladder, since this is an area where urine is stored for prolonged periods, giving stones the time to form. These stones may move into the urethra causing an acute urinary tract obstruction. The kidney, as previously mentioned, is another common site of stone formation, particularly in cats. These stones can then move down the ureter causing ureteral obstruction and a subsequent acute kidney injury.
Risk Factors
The risk of stone formation is increased where a higher concentration of stone-forming compounds are present, and where they are in contact with each other for longer periods of time. They often form around a nidus - a concentration of bacteria, white blood cells, crystals and a proteinaceous matrix and build up gradually, layer by layer, over time.
Larger crystals can also come together and merge to increase urolith size.
The risk of stone formation really depends on the individual patient, their breed, their diet, current medications, whether a urinary tract infection is present, and other factors such as frequency of urination and individual genetics.
It’s important to remember that not every patient with crystals will go on to develop stones - but they are at risk of developing them. Therefore, patients with high numbers of crystals should have these managed where appropriate (e.g. by modifying their diet if applicable to the crystal type).
Struvite Uroliths
Struvite or ‘triple phosphate’ uroliths are formed of magnesium ammonium phosphate and calcium phosphate. They form most commonly as a result of urinary tract infections with urease-producing bacteria in dogs.
The urease breaks down urea into ammonia and bicarbonate; ammonia binds with magnesium and phosphate to form the stone, and bicarbonate makes the urine more alkaline, increasing the precipitation of the struvite stones.
Sterile struvite stones are very rare in dogs, but more common in cats - as feline struvite urolithiasis is not usually associated with urinary tract infection.
Struvite stones are radio-opaque and can therefore be seen on x-ray - and can be dissolved with dietary modification - so no need to rush into a cystotomy in these patients! Instead, we feed an acidifying dissolution diet, which reduces the urine pH, dissolves the struvite stones, and maintains a more acidic environment within the bladder, to prevent more from developing. We also need to treat any urinary tract infection present with appropriate antibiotics.
The cause of struvite stone development is multifactorial and includes gender, breed and diet. Most canine struvite stones are seen in female dogs, due to their shorter urethra and higher UTI incidence. Predisposed breeds include Miniature Schnauzers, Bichon Frises, Shih Tzus, Miniature Poodles, Cocker Spaniels and Lhasa Apsos.
Calcium Oxalate Uroliths
Calcium oxalate uroliths are the most common urolith seen in cats. They are formed mostly of calcium oxalate and calcium phosphate, and usually form on the surface of other crystals, or on cellular debris within the urinary tract.
Though they most frequently form in the lower urinary tract, they can also be seen within the kidneys and ureters, particularly in feline patients.
Neutered male dogs are more frequently affected than female dogs, and overweight patients are at an increased risk of stone formation. At-risk breeds include Chihuahuas, Pomeranians, Yorkshire terriers, Miniature Schnauzers, Bichon Frises, Shih Tzus, Miniature Poodles, Cairn Terriers and Lhasa Apsos.
Calcium oxalate stones form in acidic urine and their prevalence has increased significantly over the last 20 years. It is thought that the increased use of urine-acidifying diets (designed to dissolve struvite crystals) over this time is associated with this.
Unlike struvite stones, calcium oxalate stones are not usually associated with urinary tract infection, but the stones themselves can become infected. Like struvite, they are radio-opaque, but cannot be dissolved with diet and must be managed surgically.
Though we cannot dissolve these stones with diet, we can adjust the patient’s diet to minimise the risk of more crystals/stones forming in the future. This is achieved by diluting the urine (by adding water to food or switching to a wet diet), and by using a diet with a struvite/oxalate complex (e.g. Purina St/Ox, hills c/d or Royal Canin S/O). Medications such as potassium citrate may also be administered, to reduce urine acidity and increase urine citrate excretion.
Urate Uroliths
Urate uroliths are formed of uric acid and ammonium urate. They are small, round, green-coloured stones found most commonly in the lower urinary tract. They are more commonly seen in younger patients and are more common in males than in females.
Urate stone formation is seen commonly in breeds such as Dalmatians and English Bulldogs. Dalmations have a genetic abnormality in their purine metabolism pathways, resulting in increased numbers of uric acid crystals, predisposing them to stone formation. Though all Dalmatians have the genetic abnormality, not all of them develop urate stones.
Patients with hepatic disease such as portosystemic shunt patients or end-stage liver failure patients may also develop urate uroliths. This is because the liver is unable to adequately convert ammonia into urea and uric acid, leading to an increased amount of ammonia present within the urine.
Urate stones are radiolucent, so not easily seen on radiographs (but evidence of their presence may be seen with contrast radiography). They can be managed medically, by feeding a calculolytic diet with low purine content and through the use of medications such as allopurinol.
Miscellaneous Uroliths
Several other stone types may be seen, including cystine, silica and calcium phosphate, but these are very rare compared to calcium oxalate, struvite and urate stones. Certain medications, such as tetracycline antibiotics, may also cause drug crystals to form in urine which could go on to form stones.
Prostatic Disease
Prostatic diseases are a common cause of stranguria in older, intact male dogs.
Pathophysiology
The prostate gland completely encircles the proximal urethra and bladder neck in male dogs. It is an accessory sex organ and functions to produce fluid that nourishes and prolongs the survival of sperm during reproduction. The prostate gland is usually very small in neutered dogs, as it requires a testosterone derivative to grow and develop properly.
There are three main conditions of the prostate gland - benign prostatic hyperplasia (BPH), prostatitis and infection.
Benign Prostatic Hyperplasia
BPH is the most common clinical disorder of the prostate gland seen in older dogs. It is the gradual enlargement of the prostate due to the ongoing release of testosterone and other testosterone derivatives. As the condition progresses, fluid-filled prostatic cysts can also develop.
As the enlarged prostate encircles the urethra, it compresses it, causing stranguria. On examination, these patients have a symmetrically enlarged, non-painful prostate gland.
Prostatitis
The second most common prostatic disease is inflammation of the gland or prostatitis. This can be acute or more gradual in onset; in veterinary patients, acute prostatitis is very rare. Chronic prostatitis is commonly associated with BPH, and on examination, the prostate may be painful and mildly asymmetrical. The prostate gland is not always enlarged in patients with chronic prostatitis.
Infection
Prostatic infections are commonly associated with ascending urinary tract infections which spread from the urethra to the prostate gland. Most commonly this is due to pathogens such as E.coli, Pseudomonas, Proteus and Staphylococcus/Streptococcus.
Patients may also develop chronic prostatitis with recurrent infections, as the prostate gland acts as a reservoir for the infection.
Prostatic infections can be challenging to treat, requiring antibiotics that cross the blood-prostate barrier and sit in the prostate gland in high concentration.
Diagnostics and Management
A prostatic wash is a common test performed in the diagnosis of prostatic disorders. This is usually performed under ultrasound guidance, which also allows a full ultrasound evaluation of the urinary tract and visualisation of the prostate gland.
A urinary catheter is placed in the urethra and withdrawn to the level of the prostate gland. A small amount of sterile saline is flushed through the catheter, whilst a prostatic massage is performed via rectal exam. The fluid is then aspirated back through the urinary catheter and submitted for bacterial culture and cytology analysis. Think of it as a bronchoalveolar lavage for the prostate! And yes, veterinary nurses can perform this diagnostic skill!
Treatment of prostatic disease varies depending on the underlying cause and includes neutering patients with BPH to prevent further growth of the gland, and management of prostatic infections and prostatitis with appropriate antimicrobials and anti-inflammatories.
Lower Urinary Tract Neoplasia
Transitional cell carcinoma (TCC), also known as urothelial carcinoma, is the most common cancer affecting the lower urinary tract of dogs and cats. TCCs generally arise from the bladder neck, in the trigone region, or from the urethra.
Risk Factors
Several risk factors have been identified for their development, including exposure to certain medications and pesticides, and genetics. Predispositions exist in West Highland White Terriers, Scottish Terriers, Beagles, Dachshunds and Shetland Sheepdogs. They are also more prevalent in middle-aged/senior male cats.
Clinical Signs
Stranguria, pollakiuria and haematuria are common clinical signs in patients with TCC. If the tumour completely obstructs urine flow, these patients can present as an emergency with urethral obstruction (‘blocked bladder’).
Physical Examination
An examination may be normal in these patients, or a thickened, distended urinary bladder may be evident on palpation. A rectal exam should always be performed in a patient with suspected urinary tract neoplasia; this often reveals a thickened, irregular urethra. The sublumbar lymph nodes (dorsal to the bladder) may also be enlarged - these are not usually palpable but may be if they are abnormal.
Diagnosis
Diagnostic tests commonly performed in these patients include:
Urine Analysis (do not collect a sample via cystocentesis in these patients, as this can cause tumour seeding into the abdominal wall - instead, use a urinary catheter or collect a free-catch sample)
Abdominal ultrasound (or CT)
Thoracic radiographs (or CT)
Traumatic catheter biopsy (where a urethral catheter is placed under ultrasound guidance and directed into the mass. Suction is then used to collect a sample of the mass into the urinary catheter, which is then submitted for analysis)
Cystoscopy with biopsies
Treatment and Nursing Care
Treatment is achieved with chemotherapy in most cases. A variety of agents are used in combination, such as vinblastine or mitoxantrone, either as a single agent or alongside a non-steroidal anti-inflammatory drug such as piroxicam or meloxicam to improve survival times.
Nursing care of these patients is vast, not only during diagnosis but also throughout treatment. Considerations include:
Monitoring urination (frequency, appearance and behaviour)
Aseptic management of the patient during cystoscopy or catheter placement, to prevent UTI formation
Monitoring comfort and providing analgesia
Administering chemotherapy
Collecting updated histories at each appointment
Checking haematology prior to each appointment
Discussing quality of life
Promoting general wellness and ensuring patients can perform their usual activities as well as possible
Monitoring for chemotherapy side effects and providing medications to manage this where appropriate (prescribed by the veterinary surgeon)
Providing fear-free and compassionate care so the patient enjoys coming to see you for chemotherapy and check-ups
So as you can see, there are a number of conditions causing stranguria, and their diagnosis, management and nursing considerations all vary widely! It’s really important for us to have a good understanding of these so that we can tailor our care and advice to the individual, and hopefully, now you have just that!
Which of these conditions do you see most commonly in your practice? DM me over on Instagram and let me know!
And make sure to check back next week as I’ve left FLUTD off of today’s post on purpose… we’re about to dive deep into that in our next post!
References
Foster, J.D. 2021. Managing Urolithiasis in Dogs. Today’s Veterinary Practice. Available from: https://todaysveterinarypractice.com/managing-urolithiasis-in-dogs/
Merrill, L. 2012. Small Animal Internal Medicine for Veterinary Technicians and Nurses, Iowa: Wiley-Blackwell.
