Ultrasound-Guided Urinary Bladder Biopsy Through a Urinary Catheter in a Bitch

Introduction

Urinary bladder masses can be a cause of lower urinary tract disease in dogs. Those masses can be either benign or malignant. In most cases, the benign masses are either inflammatory lesions or polyps, whereas the neoplastic masses are most likely transitional cell carcinoma, adenocarcinoma, or lymphoma.¹ Historically, transitional cell carcinoma is thought to occur in older dogs at the trigone region of the urinary bladder, and polypoid cystitis is thought to occur in younger dogs at the cranioventral aspect of the urinary bladder.^1,2 However, that observation is not always accurate, and histologic diagnosis of urinary bladder masses is often necessary as the therapeutic approach and prognosis are different depending on the underlying cause.

Case Report

A 34.4 kg 5 yr old spayed female mixed-breed dog was examined by a referring veterinarian for acute-onset hematuria and stranguria. Physical examination was unremarkable. Clinical signs did not resolve after administration of a 14 day course of ciprofloxacin. At the time of reevaluation, while preparing to obtain a urine sample via ultrasound-guided cystocentesis, a mass was noted in the urinary bladder.

The patient was referred to a specialty hospital for further work up. An abdominal ultrasound was performed, which revealed an irregular 2.75 cm × 4.79 cm mixed, echogenic mass within the urinary bladder.

At the specialty hospital, the dog was sedated by IV administration of butorphanol tartrate (0.2 mg/kg) and midazolam (0.2 mg/kg). The blunt end of a 41 cm, 10-French (Fr) rubber catheter^a was cut using a no. 10 blade just past the side hole furthest from the tip to produce an open-ended catheter without side holes. The catheter tip was examined to ensure it remained smooth. The dog was placed in sternal recumbency, and the rubber catheter was passed into the urethra using aseptic technique. A urine sample was obtained from the urinary catheter and submitted for urinalysis, culture, and sensitivity. The patient was then placed in dorsal recumbency in a foam trough. Saline was infused through the urinary catheter to distend the urinary bladder and improve visualization during ultrasonography. The mass was pedunculated and attached by a broad base at the cranioventral aspect of the urinary bladder (Figure 1).

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Using ultrasound guidance, the rubber catheter was repositioned within the urinary bladder just cranial to the urethra. Saline was infused and removed through the urinary catheter to manipulate the size of the urinary bladder and optimally position and align the bladder mass with the rubber catheter. A pair of flexible wire ellipsoid cup biopsy forceps^b (190 mm in length, 1.8 mm in diameter) was passed into the rubber catheter and advanced until noted to exit the rubber catheter (Figure 2). The forceps were opened and pulled back until the jaws of the forceps came into contact with the rubber catheter providing stability to the otherwise flexible biopsy forceps. The rubber catheter and forceps were advanced in tandem until they were observed to make contact with the bladder mass at which point a biopsy was obtained. The biopsy forceps were withdrawn from the rubber catheter to retrieve the biopsy sample with the rubber catheter remaining in place within the urinary bladder. The procedure was repeated to obtain multiple biopsies. After completion of the procedure, the urinary bladder was emptied and the rubber catheter was removed. There was no evidence of hemorrhage. The patient was discharged a few hours after completion of the procedure, and the owner did not observe hematuria on subsequent urination.

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Histopathology of the biopsy sample was consistent with polypoid cystitis. Follow-up surgical removal of the polyp was uneventful, and histopathology confirmed the presurgical biopsy diagnosis of polypoid cystitis.

Discussion

Options for sampling urinary bladder masses include cytologic analysis of samples obtained via urinalysis; traumatic catheterization or ultrasound-guided fine-needle aspiration; or histologic analysis of samples obtained via traumatic catheterization, ultrasound-guided catheter biopsy, cystoscopic-guided biopsy, or surgical biopsy.^3–5 When deciding on a procedure to obtain a sample, the clinician must understand the limitations of each procedure. Urinalysis or traumatic catheterization may reveal neoplastic cells; however, they also may be indistinguishable from reactive epithelial cells associated with inflammation, making it difficult to either confirm or deny neoplasia.^3,6 Ultrasound-guided fine-needle aspiration techniques also have the ability to reveal neoplastic cells; however, the procedure may implant tumor cells along needle tracts.⁷ Ultrasound-guided catheter biopsies require placement of the catheter side holes against the lesion, which can be technically difficult and the small size of biopsies obtained may limit the accuracy of histologic diagnosis.⁸ Cystoscopy, although minimally invasive, requires anesthesia, specialized equipment and training, and diagnostic-quality biopsies may not be obtained in male dogs.^3,5 Surgical biopsies provide adequate sampling and visualization but are invasive, can have various complications, and require anesthesia.^3,5

The minimally invasive, nonanesthetic biopsy technique described herein requires consideration as an option for obtaining mucosal biopsies of the urinary bladder. The forceps used in this procedure are reusable and easily sterilized. The rubber catheter is disposable and economical. The position of the biopsy forceps was readily visualized using ultrasonography. Use of the rubber catheter allowed for protection of the urethra from potential trauma caused by use of a pair of metal biopsy forceps and also allows for retrieval of a biopsy sample without exposing the urethra to neoplastic cells. Either infusing or removing saline via the urinary catheter allowed for not only improved visualization of the mass but also facilitated the positioning and alignment of the biopsy forceps with the bladder mass.

There are various potential limitations to obtaining biopsies via this procedure. One major limitation is the lack of direct visualization of the bladder mass, mucosa, and biopsy site. Risk of obtaining a biopsy at an area of increased vascularity could potentially cause severe hemorrhage that would be difficult to control. Another limitation is urethral diameter. Based on the instruments available at the authors’ facility, the smallest rubber catheter that the 1.8 mm biopsy forceps could be passed through was a 10-Fr diameter rubber catheter. Urethral and catheter diameter limits the above-described procedure to dogs where urinary catheterization with a 10-Fr rubber catheter can be performed. The use of smaller biopsy forceps would allow the procedure to be performed in smaller patients but may compromise the ability to obtain diagnostic samples.³ While there is risk of iatrogenic urinary tract infection with this procedure, maintaining aseptic technique will help minimize that possibility. Finally, the rubber catheter tip must be altered to allow the biopsy forceps to emerge at the opposite end. If not careful about ensuring a smooth proximal rubber catheter tip, urethral trauma could occur from passing the altered rubber catheter.

Further evaluation of this procedure in obtaining biopsies of urinary bladder masses at various locations, in dogs of different sizes, and in male dogs is needed. This report evaluated the biopsy of a mass located at the cranioventral aspect of the urinary bladder and the authors hypothesize that obtaining biopsies of bladder masses at either the trigone area or proximal urethra should be easier to perform due to its more proximal location and direct access from the urethra. This procedure would also be more easily performed in male dogs due to ease of urinary catheter placement compared with female dogs. It would also allow use of larger biopsy forceps in male dogs compared with cystoscopy. In cystoscopy, the small size of the endoscopic biopsy channel does not allow the use of biopsy forceps >1 mm diameter, leading to a lower diagnostic success rate of biopsy samples in male dogs compared with female dogs.³ A prospective study is needed to make direct comparisons on the diagnostic success between cystoscopy and the technique described in this report.

Conclusion

The technique described here for procurement of urinary bladder biopsies through a urinary catheter with ultrasound guidance allows for a less invasive nonanesthetic method of obtaining urinary bladder mass biopsies. With increasing availability of ultrasonography, this procedure should be given consideration as a method of obtaining urinary bladder mass biopsies in cases where a patient is either not stable for procedures that require anesthesia or if cystoscopy is not readily available. Further studies are needed to determine if this procedure should be considered as a first-line approach to obtaining either urinary bladder or urethral biopsies.