That Perineal Bulge Matters: Radiographic Clues to Feline Urethral Rupture

Perineal Findings Associated with Urethral Ruptures on Plain Lateral Radiographs in Cats

Jessica Milne, Tim Sparks, Robert Brash, Margarida de Almeida Coelho, Thomas Natsiopoulos, Andrew Holdsworth

Background

Urethral ruptures (URs) in cats are uncommon but potentially life-threatening injuries, most often associated with trauma or iatrogenic causes. Diagnosis can be delayed because clinical signs and biochemical abnormalities may be subtle or slow to develop. While contrast lower urinary tract studies (LUTS) are the diagnostic gold standard, plain radiographs are routinely obtained during initial assessment. The authors observed recurring perineal soft tissue changes on plain radiographs in cats later confirmed to have URs and sought to formally evaluate whether such findings could aid earlier suspicion and diagnosis.

Methods

This retrospective, multicentre, case–control study included 92 cats that underwent plain radiography including the perineal region between 2013 and 2023. Twenty-two cats had confirmed URs, while 70 cats formed a control group without URs. Two board-certified veterinary radiologists independently and blindly reviewed radiographs for perineal bulge presence and size, perineal tissue heterogeneity, and urinary bladder visibility. Associations between radiographic findings and URs were statistically analysed, along with intra- and inter-observer agreement.

Results

A perineal bulge was identified in 95.5% of cats with URs, yielding high sensitivity and negative predictive value but low specificity. Larger perineal bulge size was significantly associated with URs, with traumatic ruptures producing more pronounced bulges than iatrogenic injuries. Heterogeneous perineal soft tissue opacity was also strongly associated with URs and showed higher specificity than bulge presence alone. Pelvic fractures were associated with perineal bulging but not directly with URs. Visibility of the urinary bladder on radiographs did not exclude UR. Reviewer suspicion based on plain radiographs correlated strongly with confirmed URs and recommendations to perform LUTS.

Limitations

The study was limited by its retrospective design, small number of confirmed UR cases, and variability in radiographic quality, positioning, and timing relative to catheter placement. Not all control cases underwent LUTS or surgical confirmation, raising the possibility of misclassification. Body condition scoring was inconsistently recorded and not formally analysed.

Conclusions

Plain radiographic findings—specifically the presence of a perineal bulge, increased bulge size, and heterogeneous perineal soft tissues—are significantly associated with urethral rupture in cats. Although these findings lack specificity and cannot confirm UR, their high sensitivity makes them valuable for raising clinical suspicion and prompting timely LUTS. Careful scrutiny of the perineal region on routine radiographs may therefore reduce diagnostic delays and improve clinical outcomes in cats with suspected URs.

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