URETHRAL STENTING FOR MALIGNANT OBSTRUCTION

Initial findings

  • Signalment: 8-year-old male castrated beagle (22 kg)
  • Presenting complaint: Progressively worsening stranguria with near complete urinary obstruction
  • Pertinent history: Recent history (four months previously) of suspected urinary tract infection that did not improve with antibiotics; Follow-up ultrasonography and prostatic fine-needle aspirate diagnosed urothelial carcinoma
  • Medications: Piroxicam (5mg PO SID), Misoprostal (50ug PO BID)
  • Physical examination findings: Quiet, alert, and responsive; Heart rate 140 bpm; body condition score 5/9; Multiple soft moveable subcutaneous masses; Moderate bilateral hindlimb muscle atrophy; Very large caudal abdominal structure consistent with distended urinary bladder; Large, firm, lobulated, irregular prostate palpated on rectal examination, lumbar lymph nodes not palpable on rectal examination; Drops of urine dripping from prepuce

Diagnostic evaluation

  • Complete blood count: Mild stress leukogram
  • Serum chemistry profile: ALT 79, AST 39, ALP 420
  • Abdominal radiography: Enlarged, mineralized prostate; Hepatomegaly
  • Thoracic radiography: Unremarkable
  • Abdominal ultrasonography: Soft-tissue mass located at urinary bladder trigone and extending into/from proximal urethra; Intra-pelvic urethra not visualized; Lumbar lymph nodes within normal limits; No evidence of hydroureter or hydronephrosis; slightly enlarged hyperechoic liver; Remaining structures unremarkable
  • Urinalysis / Urine Culture: Pending

Treatment decisions
This patient was determined to have a complete or near complete urethral obstruction due to the progressive urothelial carcinoma. An 8Fr urethral catheter was placed in the emergency room and 400 ml of hematuria was removed from the urinary bladder. The elevated heart rate came down following bladder drainage. Discussion with the owner included surgery (cystostomy tube), radiation therapy (palliative or full course) with periodic urinary catheterization (BID-TID) until urethral patency, or urethral stenting. Tumor extension into the trigone, as well as prostatic involvement, made complete surgical resection an unlikely option. Medical management (chemotherapy) was discussed but acute response permitting urination was unlikely. The owner chose urethral stenting as a rapid, effective, minimally-invasive, out-patient procedure shown to provide immediate relief of stranguria by immediate restoration of a patent urethra.

The patient was placed under general anesthesia and positioned in lateral recumbency and the urinary catheter was removed. A 4Fr angiographic marker catheter was placed within a 14Fr red rubber catheter that was advanced per rectum into the descending colon (Figure 1). This marker catheter would be used to calculate radiographic magnification. The prepuce was clipped, scrubbed and draped. All wire, catheter, and stent manipulations were performed under fluoroscopic guidance. A 0.035” angled hydrophilic guidewire was placed transurethrally and advanced into the urinary bladder. An 8Fr introducer sheath was advanced over the guidewire and secured to the prepuce with a single nylon suture. A 4Fr berenstein catheter was advanced over the wire, through the introducer sheath, and into the urinary bladder. The guidewire was removed, a sample of urine is collected for culture, and a 1:1 combination of iodinated contrast and sterile saline was injected until the urinary bladder was full. A urethrogram was then performed with the same contrast mixture through the introducer sheath in order to distend the urethra and define the extent and location of the urethral obstruction (Figure 2). Maximal urethral diameter was then determined and an appropriately-sized laser-cut, nitinol, self-expanding metallic stent (SEMS) was chosen. The berenstein catheter was removed over the guidewire and the stent delivery system was advanced over the guidewire across the urethral obstruction (Figure 3). The stent was deployed across the urethral obstruction and a repeat urethrogram was performed through the introducer sheath to confirm urethral patency (Figure 4). A final radiograph was obtained, the guide wire and introducer sheath were removed and the patient was recovered.

Outcome
This patient was discharged from the hospital the same day with immediate resolution of the urethral obstruction. Discharge medications included a 2-week tapering dose of enrofloxacin pending the urine culture results. Initially he would drip urine on occasion between normal strong urinations, but this resolved after the first week. A recheck examination was scheduled two weeks later with an oncologist to discuss further treatment options.

Discussion
Malignant urethral obstructions can cause life-threatening biochemical changes in veterinary patients. Urothelial/Transitional cell carcinomas are the most common lower urinary tract tumors encountered in dogs, often involving the trigone, urethra, and/or prostate. Greater than 80% of these patients experience significant dysuria and approximately 10% of these patients progress to develop complete urinary tract obstruction. 1,2 While chemotherapy has been demonstrated to result in improved survival times, substantial tumor responses are uncommon, complete cures are rare, and tumor progression is typical. Once signs of urinary obstruction occur, few good options exist. Cystostomy tube placement, transurethral resection, and surgical diversion have been described but are either invasive or associated with significant morbidity including need for manual urine drainage, tube dislodgement, urinary tract infection, incontinence, and/or surgical complications).3-6  More recently, transurethral placement of self-expanding metallic stents (SEMS) under fluoroscopic guidance has been described which results in rapid and effective restoration of urethral patency and urine flow. 7 These procedures are performed on an out-patient basis and avoid the need for manual drainage and other surgical-associated complications. A recent study reported good results following urethral stent placement in 42 dogs; a major incontinence rate of 25% (3/4 dogs had minor or no incontinence) and median survival time of approximately 250 days if the patients received chemotherapy following stent placement.8 The cause of death in these patients is rarely due to repeat urinary obstruction; the most common cause of death is secondary to tumor metastases and signs of systemic illness. These stenting techniques have also been effective in cats as well as for malignancy or benign urethral strictures.

A video of the procedure can be viewed at http://www.amcny.org/node/342#Urethral_Stenting. The stenting procedure is fairly short and the patients are typically discharged from the hospital the same day. Medical management with antibiotics (short-term), NSAIDs, and chemotherapy continue post-stenting. For more case studies and to see how interventional radiology and interventional endoscopy can benefit patients, visit http://www.amcny.org/interventional-radiology-endoscopy/IR-IE-procedures.

Submitted by Dr Chick Weisse VMD, DACVS

References

1 Norris AM, Laing EJ, Valli VEO, et al. Canine bladder and urethral tumors: a retrospective study of 115 cases (1980–1985). J Vet Intern Med 1992;16:145–153.

2 Knapp DW, Glickman NW, DeNicola DB, et al. Naturally occurring canine transitional cell carcinoma of the urinary bladder. A relevant model of human invasive bladder cancer. Urol Oncol 2000;5:47–59.

3 Stiffler KS, McCrackin Stevenson MA, Cornell KK, et al. Clinical use of low-profile cystostomy tubes in four dogs and a cat. J Am Vet Med Assoc 2003;223:325–329.

4 Liptak JM, Brutscher SP, Monnet E, et al. Transurethral resection in the management of urethral and prostatic neoplasia in 6 dogs. Vet Surg 2004;33:505–516.

5 Stone EA, Withrow SJ, Page RL, et al. Ureterocolonic anastomosis in ten dogs with transitional cell carcinoma. Vet Surg 1988;17:147–153.

6 Weisse C, Berent A, Clifford C, et al. Evaluation of palliative stenting for management of malignant urethral obstructions in dogs. JAVMA, Vol 229, No. 2, July 15, 2006

7 Blackburn A, Berent A, Weisse C, et al. Urethral Stenting in Canine Patients with Urothelial Carcinoma: A Review of 41 Cases (2004-2008). ACVIM, 2010.

 

 

FIGURES

Figure 1: Lateral caudal abdominal static fluoroscopic image demonstrating marker catheter in descending colon (black block arrows) and guidewire (white arrows) placed retrograde into the urethra and urinary bladder.

 urethralstent1  

Figure 2: Lateral caudal abdominal fluoroscopic image obtained during retrograde contrast urethrocystogram demonstrating normal penile urethra but narrowed prostatic urethra (white arrows) with contrast extravasation into prostatic tumor. There is also a filling defect in the bladder dorsal bladder trigone (white arrows).Urethralstent2

 

Figure 3: Lateral caudal abdominal static fluoroscopic image demonstrating stent delivery system placed over the guidewire and the compressed radio-opaque stent (white arrows) placed across the malignant obstruction prior to stent deployment.Urethralstent3

 

Figure 4: Lateral caudal abdominal fluoroscopic image obtained during a repeat retrograde contrast urethrocystogram demonstrating the deployed stent (white arrows) and a patent urethra.Urethralstent4

 

 

 

 

 

 

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