Study makes canine urolithiasis and PPVH link

Researchers have called for clinicians to be vigilant for urinary tract disease when treating dogs with primary portal vein hypoplasia (PPVH).

In a retrospective study, published in the Journal of Small Animal Practice, scholars searched clinical records of 15 UK referral hospitals for dogs diagnosed histopathologically with PPVH between 2010 and 2023, excluding those diagnosed with congenital portosystemic shunt (PSS).

Of the 14 dogs that ultimately met the strict inclusion criteria, four (28.6%) had urolithiasis, all of which had crystalluria and showed gastrointestinal signs.

Clinical signs

One of the four dogs had bilirubin crystals while the three others with urolithiasis had ammonium biurate crystalluria, and two exhibited lower urinary tract signs.

Three of the four were also diagnosed with cystoliths, including one dog with concurrent multifocal obstructive ureterolithiasis.

Acquired extrahepatic PSS was documented in half of the dogs with urolithiasis but in just one of 10 dogs without.

The median age at diagnosis was 15 months and 39 months in dogs with and without urolithiasis, respectively, while the median duration of clinical signs was 71 days and 135 days.

Importance

The authors argued their findings highlighted the importance of performing urinalysis and diagnostic imaging in the evaluation of dogs with PPVH.

They noted the small sample size reflected their strict diagnostic criterion rather than how frequently PPVH was encountered in clinical practice, and that they cannot draw firm conclusions about prevalence or causation.

However, they concluded that recognising the prevalence of urolithiasis in dogs with PPVH is “essential to increase awareness of this potential complication – particularly the risk of urinary obstruction – and ultimately to help refine prevention strategies” and called for future studies to consider a wider population of young dogs with a high suspicion of PPVH.

‘Closer look’

First author Victoria Travail, European specialist in companion animal internal medicine, said: “For clinicians, I think our findings support taking a closer look at the urinary tract when investigating dogs with PPVH.

“A urinalysis is relatively simple and non-invasive, and the presence of crystalluria may provide an additional indication that further investigation is warranted. Diagnostic imaging is also important – particularly because urolithiasis may be present even when urinary signs are not the main presenting complaint.”

She emphasised the absence of lower urinary tract signs did not necessarily exclude urolithiasis and that the findings also highlighted that the relationship between PPVH, crystalluria and urolith formation is likely to be more complex than simply assuming that every dog with PPVH will develop urate uroliths.

Assessments

Dr Travail concluded: “I think the most useful takeaway for vets in practice is not that every dog with PPVH will develop urolithiasis, but rather that these dogs should be recognised as potentially being at increased risk.

“Incorporating urinalysis into their assessment and considering diagnostic imaging of the urinary tract may help identify crystalluria or urolithiasis that might otherwise go unnoticed.

“Further prospective studies involving larger numbers of dogs are needed to establish the true prevalence of urolithiasis in PPVH and to determine which individual dogs are at greatest risk.

“Our study is, therefore, best viewed as highlighting an important clinical association and generating questions for future research, rather than establishing definitive risk factors.”