N Shimizu 1, A Hamaide 1, E Soliveres 1, M Heimann 2, S Noel 1, G Bolen 1
Background
Definitive diagnosis of canine urinary bladder lesions, such as urothelial carcinoma, often requires tissue histopathology. Existing biopsy methods include fine-needle aspiration, brush cytology, cystotomy, laparoscopy, and cystoscopy, each with limitations related to invasiveness, risk of tumor seeding, or anatomical constraints. This study aimed to evaluate the feasibility, safety, and diagnostic utility of a minimally invasive, ultrasound-guided transurethral biopsy technique using endoscopic forceps in a diverse canine population.
Methods
A retrospective analysis was conducted on 27 dogs undergoing ultrasound-guided transurethral bladder biopsy using endoscopic forceps from 2016 to 2019. Data collected included signalment, lesion location, use of a urinary catheter, procedural success, histopathological findings, and post-procedural outcomes. Biopsies were performed under general anesthesia with or without a urinary catheter, and Doppler ultrasound was used to avoid vascular areas. Samples were evaluated histopathologically for diagnostic adequacy.
Results
The biopsy procedure was successful in 23 out of 27 dogs. In smaller dogs or those with urethral obstruction, direct forceps insertion (without a catheter) was feasible and safe. The procedure failed in four dogs due to small urethral diameter, urethral obstruction, or difficulty grasping lesions. No major complications were observed. Histopathological analysis provided a definitive diagnosis in all successful cases, with most being urothelial carcinoma. Sample sizes varied but were consistently sufficient for diagnosis. Follow-up confirmed clinical improvement or stability in dogs with non-neoplastic diagnoses.
Limitations
This was a retrospective study with a relatively small sample size and lacked standardization in biopsy technique, lesion accessibility, and post-procedural monitoring. The procedure's feasibility in extremely small or male dogs was limited by anatomical constraints, and exact procedural duration was not consistently recorded.
Conclusions
Ultrasound-guided transurethral biopsy using endoscopic forceps is a safe and effective technique for diagnosing bladder lesions in dogs. It is especially useful when endoscopy is not feasible. The approach minimizes invasiveness, avoids the risks associated with open surgery or percutaneous biopsy, and enables histopathological evaluation even in cases with vascular lesions. The technique is contraindicated in dogs with urethral diameters under 1.8 mm due to obstruction or small body size.
Sequence ultrasonographic images during the procedure. (A) Insertion of the urinary catheter (*) seen as a hypoechoic band surrounded by two hyperechoic lines. The urinary catheter alone was inserted up to the lesion. (B) Insertion of the biopsy forceps (arrow) inside the urinary catheter. The forceps gives a strong comet-tail reverberation artefact due to the metallic material. (C) The opened biopsy forceps (arrowhead) was advanced in front of the lesion before closing it and retrieving the biopsy
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