Summary of the ACVIM Consensus Statement on Diagnosis and Management of Urinary Incontinence in Dogs

By Daniela Ackley, DVM, DACVIM
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April 2024

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At one time, dogs lived in the backyard, and incontinence was not a serious issue; however, as dogs have moved into the home and sometimes owners’ beds, their ability to control the timing of urination has become essential. As a result, incontinence has become a major source of frustration for owners and their veterinarians.

There are a few review articles addressing urinary incontinence (UI) but no large prospective clinical trials comparing treatment outcomes. Therefore, the objectives of the ACVIM consensus statement were to provide guidelines on both recommended diagnostic testing and treatment for different causes of UI in dogs.

This consensus was created by a panel of 12 experts, including eight small animal internists, two neurologists, one radiologist, and one surgeon.¹

Definition

UI is a disorder of micturition characterized by the passive, involuntary leakage of urine. Although the exact prevalence of acquired UI in dogs is unknown, studies have reported a 3% to 20% prevalence in spayed female dogs. The prevalence of acquired UI in male dogs is much lower, and the underlying causes are less well understood. An article published in 2019 from the UK² found a prevalence of 0.9% in male dogs, with bull mastiffs and Irish red setters being overrepresented.

Classification

The panel’s first question was how canine UI should be classified. All the panel members agreed that UI should be divided into disorders of storage and disorders of voiding.

Pic. 1 This flowchart shows two main categories: disorders of storage and disorders of voiding. These can further be subdivided into major causes.

Disorders of storage are characterized by normal postvoiding residual volume (small urinary bladder), and voiding disorders are characterized by urine retention with increased post-void residual volume (bladder remains large after urination). Both disorders can be subdivided into functional and mechanical causes.

Female dogs are more likely to experience storage disorders, while male dogs experience storage and voiding disorders with equal prevalence.

Important history questions that should be asked when assessing a patient with UI:

• Is the dog aware of inappropriate urination? (is it really incontinence?)
• How long has the problem been present?
• Was the problem present before neuter?
• Is the dog able to urinate normally?
• Is there a change in the frequency of normal urination?
• Is the dog polyuric/polydipsic?
• Can the dog produce a normal urine stream?

The author sees PU/PD commonly in dogs with UI. Polydipsia can exacerbate UI and needs to be diagnosed and treated. Otherwise, UI may not be managed successfully.

Direct observation or video review of a patient’s incontinence and conscious voiding behaviors is often helpful.

A thorough physical exam should be performed on all dogs, including a rectal exam with urethral palpation and a focused neurologic examination that assesses behavior, gait, hindlimb postural reactions, spinal reflexes, tail tone, and the presence of back pain.

Post-void residual volume (PVRV) should be assessed in all dogs, especially males, presenting with UI. An increased PVRV could signify a disorder in voiding, whereas a normal PVRV suggests a urine storage disorder (100% agreement from the panel). Techniques used to measure PVRV in dogs include urinary bladder palpation, direct measurement via urinary catheterization, 2-dimensional (2D) B-mode ultrasound (US) calculations, and 3-dimensional (3D) US measurements.

Pic 2. Two-dimensional ultrasound images depicting width (“B” calipers) and depth (“A” calipers) measurements in transverse (A) and length (“A” calipers) measurements in longitudinal (B).³

 2D B-mode US or a 3D US should be used instead of urinary catheterization when available. This approach is less invasive and avoids potential catheter-associated UTI, which has been reported in 8% to 32% of dogs. When using 2D ultrasonography, the formula V = length × width × height × 0.52 is the most accurate in humans and dogs for calculating PVRV.

Postvoiding residual volume should be measured within 10 minutes of voiding for accuracy, and the dog should be given enough time to fully urinate outside, particularly in male dogs that may not voluntarily void during a single posture and may need multiple attempts.

Based on recommendations in humans and clinical experience in dogs, these are the reference ranges for PVRV:

A urinalysis (UA) and urine culture and sensitivity (UC) should be evaluated in ALL dogs presented for UI, as well as in dogs with relapsing UI. Alternatively, cage-side, rapid screening for bacteriuria could be performed, and if positive, urine should be submitted for UC.

If bacterial growth is documented, antimicrobials based on susceptibility test results should be administered for five days, based on ISCAID (International Society for Companion Animal Infectious Diseases) guidelines, and monitoring for improvement in UI is recommended.

 Diagnosis of the most common storage disorder, USMI, is usually done based on appropriate signalment, history, absence of abnormalities on PE/neurologic exam, and response to an appropriate therapeutic drug trial.

Imaging

Evaluation of survey abdominal radiographs (including the entire urethra) may be considered during initial presentation for a voiding disorder. The abdominal radiographs can aid in the exclusion of mechanical voiding disorders such as uroliths in many instances, mineralized mass lesions of the lower urinary tract, or lesions of the os penis.

Pic 3. Depicting positioning of pelvic limbs in male dogs to visualize urethroliths (Clinicians Brief).

Radiographs are useful for noticing bladder position and should include the pelvis and perineum. The pelvic limbs should be extended cranially in male dogs to expose more of the penile urethra (Pic 3).

Abdominal ultrasonography (US) is a reasonable non-invasive imaging modality for screening dogs suspected of having EU before cystoscopy and can identify upper urinary tract comorbidities.

Abdominal US had reasonable sensitivity and specificity in a 2022 study from Royal College⁴ (sensitivities of 90% and specificities of 86% to 100% relative to cystoscopy) for detecting EU.

Pic 4. Sagittal US image of the urinary bladder of a dog with a right intramural EU (between calipers) can be seen as a tubular structure encroaching into the bladder lumen and following the bladder wall caudally.⁴

Ultrasonography also is excellent for assessing the remainder of the urogenital tract, such as the kidneys, as the presence concurrent urinary tract abnormalities were observed in 100% of dogs with EU including renal pelvis dilation (74%), ureteral dilation (68%), intra-pelvic bladder (19%), reduced cortico-medullary definition (23%), renal dysplasia (3%), pyelonephritis (3%), and ureterocele (3%).

Cystoscopy and CT are the most sensitive and specific imaging modalities for establishing a diagnosis of EU. However, cystoscopy is more sensitive and definitive and allows for ablation of intramural ectopic ureters when present, which is, therefore, the preferred modality.

Pic 5. Two cystoscopic images;⁴

A. An image showing bilateral ectopic ureteral orifices emptying in the vestibule of a female dog. A persistent paramesonephric septal remnant (PPSR) can also be observed, causing stenosis to the vaginal vestibule (demarcated by white asterisks).

B. An image showing a unilateral right-sided intramural ectopic ureter emptying into the mid-urethra of a female dog.

Pic 6. Cystoscopic image of laser ablation of an EU.⁵

The panel recommends flexible cystoscopy in male dogs with storage disorders that failed to respond to phenylpropanolamine (PPA) prior to testosterone treatment.

Medical treatment of incontinence in male dogs is less rewarding. Only 44% of male dogs improve with PPA, and only 38% of male dogs became continent on testosterone and testosterone treatment can be associated with serious side effects, including aggression and prostatomegaly.

Treatment

An alpha-agonist (e.g., PPA) or administration of estrogen compounds (e.g., diethylstilbestrol, estriol) is recommended as the initial treatment for USMI in female dogs. An alpha-agonist (PPA) is recommended as the initial treatment for USMI in male dogs.

Tab 1. Summary of medications for USMI in females, doses, and potential adverse effects.

Alpha-agonists stimulate the adrenergic receptors of the internal urethral sphincter, and estrogens upregulate the expression of such receptors as well as have trophic effects on the urethral sphincter.

Panelists agreed that either may be used as a first-line treatment considering potential side effects in each individual dog. No studies directly compare the treatment efficacy of PPA and estrogens; however, all eight internists on the panel chose PPA as the initial treatment. They recommend a minimum of 28 days to assess response to treatment.

Most internists choose estriol as their next treatment in dogs that do not respond to PPA.

Options for dogs that have medically-unresponsive USMI, normal cystoscopy, and negative bacterial urine culture include surgical procedures, urethral bulking, stem cell therapy, and placement of hydraulic urethral sphincter or transobturator vaginal tape.

Urethral Bulking

Urethral bulking is performed as a cystoscopic injection of a bulking agent (insoluble collagen) submucosally in the proximal urethra with an 80% response rate. However, the effect is only temporary (6–12 months).

Panelists recommend bulking agents in older female dogs as they are not as successful in dogs with concurrent anatomic abnormalities (short urethra, EU).

Pic 7. Cystoscopic injection of a bulking agent (insoluble collagen) submucosally.⁶

Artificial Urethral Sphincter

The most successful long-term treatment option for refractory UI is an artificial urethral sphincter, a hydraulic cuff placed around the urethra via an open surgery (PIC). We see good to excellent continence in 82% to 92% of dogs for two to three years.⁸

Functional Outflow Obstruction (FOO)

Idiopathic FOO was formerly known as reflex dyssynergia or detrusor urethral dyssynergia (DUD). This consensus does not recommend using the old terms as DUD specifically describes functional urethral obstruction resulting from CNS disease in humans. A definitive diagnosis of DUD requires urodynamic testing.

Idiopathic FOO occurs most commonly in large breed, middle-aged, male (neutered or intact) dogs. A typical voiding pattern starts with a normal urine stream that quickly turns into intermittent spurts, causing incomplete bladder emptying and increased PVRV. Mechanical causes for outflow obstruction (e.g., urethroliths, mass lesions) must be excluded by cystourethrogram or cystoscopy to diagnose FOO.

The recommended initial treatment in dogs with FOO is an alpha-antagonist with or without a skeletal muscle relaxant.

Tab 2. Summary of medications, doses, and potential adverse effects for treating storage disorders.

Tab 3. Summary of medications, doses, and potential adverse effects for treating voiding disorders.

Mechanical Outflow Obstruction

Mechanical obstruction in dogs most often is intraluminal or extramural, including urolithiasis, bladder or urethral neoplasia or both, proliferative urethritis, urethral strictures, urethral foreign bodies, urethral blood clots, and prostatic disease. Extramural diseases are less likely to cause complete or partial urethral obstruction and can include caudal abdominal, perineal, or penile tumors and trauma, particularly of the pelvic canal or penis. Treatment for mechanical obstructions should be considered an emergency because both systemic and local effects can be detrimental.

Timing of Gonadectomy

The recommendation of this consensus panel is to delay OHE/OVE until at least the first estrus in breeds at risk of UI or in prepubertal female dogs that already have UI. No current evidence suggests a similar timeline for neutering in male dogs. However, the panel recommends that intact male dogs with voiding disorders be neutered to decrease the prostatic size and prevent androgen-related disorders (e.g., idiopathic FOO).

Tab 4. Visual aid for diagnosis and management of UI in female dogs based on initial pattern recognition.

Tab 5. Visual aid for diagnosis and management of UI in male dogs based on initial pattern recognition.

References

1. ACVIM Consensus Statement on Diagnosis and Management of Urinary Incontinence in Dogs. Journal of Veterinary Internal Medicine. 865-1271, March 2024.
2. Hall J.L.: Urinary Incontinence in Male Dogs Under Primary Veterinary Care in England: Prevalence and Risk Factors. Journal of Small Animal Practice. Volume 60, 86-95. February 2019.
3. Kendall A.: Three-dimensional Bladder Ultrasound for Estimation of Urine Volume in Dogs Compared with Traditional 2-dimensional Ultrasound Methods. Journal of Veterinary Internal Medicine. Volume 34, 2460-2467. 2020.
4. Taylor O. Ultrasonography as a Sensitive and Specific Diagnostic Modality for the Detection of Ectopic Ureters in Urinary Incontinent Dogs. Veterinary Radiology and Ultrasound. Volume 63, 328-336. 2022.
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