Four-Holed and Fearless: Diagnosing Dog Bladder Tumors with a Twist

Journal of Veterinary Science 2025

Author

Obi Veterinary Education
March 27, 2026

Jisu Lee, Ul Soo Choi, Minji Kwon, Hakyoung Yoon

Background
Urothelial carcinoma (UC) is the most common bladder tumor in dogs and poses diagnostic challenges due to imaging overlap with benign conditions. Accurate cytological diagnosis is crucial for guiding therapy, but current methods like cystoscopy or surgical biopsy can be invasive, technically demanding, or risk tumor seeding. This study evaluates a novel approach—ultrasound-guided modified traumatic catheterization using a four-hole catheter—to improve cytological sampling efficiency and safety in diagnosing bladder masses.

Methods
The study included 15 dogs with hematuria and mass-like bladder lesions on ultrasound between 2021 and 2024. A modified 6- or 8-French feeding tube with four strategically placed holes was used under ultrasound guidance to aspirate cells from the lesion. Procedures were conducted without anesthesia or sedation. Sampling success, procedural time, and qualitative parameters—visualization, manipulation, and cellularity—were assessed. Cytological diagnosis and adverse effects were recorded.

Results
The modified technique achieved a 100% cell acquisition rate with high cellularity across all 15 cases. Median scores were 3/3 for catheter visualization and manipulation, and 2/2 for cellularity. The average procedure time was 8.8 minutes. Cytological diagnoses included 12 cases of UC and 3 cases of polypoid cystitis or bladder polyps. No significant adverse effects, such as bladder perforation or urethral trauma, were observed. Mild bleeding occurred in some cases but resolved spontaneously.

Limitations
The study lacked a control group using traditional 2-hole catheters, and no statistical comparisons were made to evaluate efficacy differences. It also did not assess long-term complications such as urethral seeding or infection, and relied heavily on cytological interpretation, which may be limited in differentiating well-differentiated neoplasia from inflammation. Additionally, inter-rater reliability for scoring and follow-up with histologic confirmation were limited.

Conclusions
The modified four-hole traumatic catheterization is a safe, quick, and effective technique for cytological diagnosis of canine bladder masses, especially UC. Its minimal invasiveness and applicability to small dogs make it suitable for widespread clinical use. Repeatable and cost-effective, the method holds promise as a first-line diagnostic tool, though further comparative and long-term studies are warranted to validate its diagnostic accuracy and safety profile.

Illustrations and ultrasound images depicting a 4-hole catheter and the modified traumatic catheterization procedure.
(A) Two additional holes were created at the tip of the catheter, resulting in four holes oriented in different directions. (B) Using ultrasound, the catheter hole was positioned to contact the protruding lesion (red dotted circle). (C) The catheter hole’s contact with the protruding lesion was confirmed using ultrasound (red dotted circle), and the catheter was then pulled toward the urethra (green arrow). (D) When the catheter’s hole separated from the protruding lesion with a ‘pop’ (red dotted circle), the pulling was stopped. The catheter remained inside the bladder (yellow arrow). (E) Under ultrasound guidance, the catheter was rotated (black curved arrow) to position a different end hole against the lesion (blue dotted circle).

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