The introduction of laser surgery to veterinary medicine about 15–20 years ago has allowed the minimally invasive treatment of a number of a conditions that would otherwise not have been possible. Applications of laser surgery to the lower urinary tract will be covered in this talk.
There are 2 types of lasers commonly used for the urinary tract:
1. Diode laser: excellent cutting and coagulating capacities for soft tissue.
2. Holmium Yag: good cutting and coagulating capacities and has the ability to fragment uroliths (lithotripsy).
Cystoscopy and Intracorporeal Lithotripsy
Urolith removal in female dogs and cats and some male dogs. Male cats, small male dogs or patients with large stone burdens should undergo PCCL.
Under general anesthesia, a retrograde urethrocystoscopy is performed. Smaller uroliths are removed using a stone basket. Larger uroliths are fragmented by a holmium: Yag laser. Direct contact of the tip of the laser fiber is required. Once fragments are small enough, they can be removed using the stone retrieval basket. Smaller fragments and debris can also be voided by urohydropulsion.1,2
Performing this procedure in a patient with a urinary tract infection is not recommended due to increased risk of urosepsis. Antibiotic therapy based on culture/sensitivity is recommended for 5–7 days prior to performing this procedure. Potential complications include urethral tears, strictures and bleeding. Bladder wall damage and perforation are possible complications but can be limited by avoiding contact of the laser/lithotripter with the urethral or bladder mucosa. Risk of incomplete stone fragment removal is higher in males (20–30%) than in females due to the difficulty in removing stone fragments by voiding urohydropulsion in male dogs.
Cystoscopic-Guided Laser Ablation of Intramural Ectopic Ureters
Ectopic ureters are characterized by one or both ureters inserting at a site outside of the bladder. Intramural EUs enter the bladder wall normally but tunnel distally in the submucosa through the trigone before inserting caudal to the urethral sphincter. Extramural EUs bypass the bladder before ending caudal to the urethral sphincter.
The recorded locations of ectopia in females are the vesico-urethral junction, proximal portion of the urethra, mid-urethra, distal portion of the urethra and vestibule, with a majority (45.8%) identified in the distal urethra. In males, the vesico-urethral junction, preprostatic and prostatic urethra have been recorded with a majority (36%) identified in the preprostatic urethra.
As >95% of EUs are intramural in female dogs, cystoscopic-guided transurethral laser ablation of intramural EU has emerged as a minimally invasive alternative to surgical correction and become the standard of care. Male dogs may have a higher incidence of extramural ectopia and therefore a retrograde cystourethrogram is essential to confirm the intramural course of the ureter prior to laser ablation.
Cystoscopy, vaginoscopy and fluoroscopy-guided retrograde cysto-urethro-ureterography are performed under anesthesia to identify the site of the ectopia, identify concurrent anomalies and confirm the intramural course of the ectopic ureter. A laser fiber, holmium:YAG or diode, is inserted through the operating channel of the cystoscope. The medial wall of the ectopic ureter is transected until the ureteral orifice inserts cranial to the urethral sphincter well within the trigone. Correction of ectopic ureter in male dogs can be technically challenging and often requires a percutaneous perineal approach.3-5
Diagnosis of ectopic ureters is made/confirmed by cystoscopy and fluoroscopic-guided retrograde ureterogram. Advanced imaging, such as CT, is rarely required unless other anomalies are suspected (vascular). Dogs with EU frequently have various other anomalies of the genitourinary tract (e.g., vestibulovaginal remnants [93%], urethral sphincter mechanism incompetence [USMI], hypoplastic bladder, pelvic bladder). Incontinence may persist after the procedure because of these concurrent urinary tract anomalies.
Cystoscopic laser ablation results in continence rates of 47% in female dogs 6 months following the procedure. Continence rates increase to 77% with the addition of medical, cystoscopic or surgical therapy for urethral sphincter mechanism incompetence. Success rates are higher in male dogs (83–100%). The procedure is well tolerated and can be done on an outpatient basis. Cystoscopic laser ablation has similar treatment outcomes as compared to open surgical management and recurrence of the ectopia and stricture at the site of the new ureterovesicular orifice, the main complication with surgical management, has been rarely reported.
Laser Ablation of Bladder/Urethral Masses
Laser ablation can be performed for debulking/removal of both neoplastic and benign bladder and urethral masses. Ablation may reestablish a urine stream in cases of complete malignant obstruction.
Under general anesthesia and ultrasound guidance, the cystoscope is advanced to within 2–5 mm of the tumor to allow precise viewing and control of the laser fiber. Ultrasonographic monitoring to allow tumor ablation without penetration of the bladder or urethral wall (masses in the distal 2/3 of the urethra are not visible on ultrasound). The resulting denatured, avascular tissue will slough within several days. Either a diode or holmium:YAG laser can be used for ablation.
Perforation of the bladder or urethral wall can lead to tumor seeding of the abdomen and require hospitalization with a urinary catheter.
Long-term success with laser ablation of bladder and urethral polyps have been reported. Ablation of transitional cell carcinomas has been described and is referred to as UGELAB.6 This procedure is considered palliative and chemotherapy should be maintained to improve outcome (mean survival time of 380 days). Despite relief of urethral obstruction, many dogs remain persistently dysuric and pollakiuric, which can improve over time. Bacterial cystitis (reported in 50% of cases postoperatively) or tumor regrowth/spread should be considered if lower urinary tract signs recur. Patients may undergo multiple laser treatments and follow-up ultrasound can aid in early identification of tumor recurrence.
1. Adams LG, Berent AC, Moore GE, Bagley DH. Use of laser lithotripsy for fragmentation of uroliths in dogs: 73 cases (2005–2006). J Am Vet Med Assoc. 2008;232:1680–1687.
2. Defarges A, Dunn M. Use of electrohydraulic lithotripsy to treat bladder and urethral calculi in 28 dogs. J Vet Intern Med. 2008;22:1267–1273.
3. Anders KJ, McLoughlin MA, Samii VF, et al. Ectopic ureters in male dogs: Review of 16 clinical cases (1999–2007). J Am Anim Hosp Assoc. 2012;48(6):390–398.
4. Berent AC, Weisse C, Mayhew PD, et al. Evaluation of cystoscopic-guided laser ablation of intramural ectopic ureters in female dogs. J Am Vet Med Assoc. 2012;240(6):716–725.
5. Berent AC, Mayhew PD, Porat-Mosenco Y. Use of cystoscopic-guided laser ablation for treatment of intramural ureteral ectopia in male dogs: four cases (2006–2007). 2008;232(7):1026–1034.
6. Cerf DJ, Lindquist EC. Palliative ultrasound-guided endoscopic diode laser ablation of transitional cell carcinomas of the lower urinary tract in dogs. 2012;240(1):51–60.