Denudation of the entire mucosa of the canine urinary bladder using the neodymium:YAG laser with the MTR 1.5 contact probe

Normal Porcine Ureter Retains Lumen Wall Integrity but Not Patency Following Catheter-Directed Irreversible Electroporation: Imaging and Histologic Assessment over 28 Days

PURPOSE

To evaluate the effect of catheter-directed irreversible electroporation (IRE) on the integrity, patency, and function of the normal porcine ureter.

MATERIALS AND METHODS

A catheter-mounted electrode was used to perform fluoroscopy-guided IRE in 8 healthy pigs. Two unilateral ablations (90 pulses at 2,000 V, 100 μs) were performed in each animal in the proximal and distal ureter. Serum creatinine measurements and contrast-enhanced computed tomography imaging were performed at 1, 7, 14, 21, and 28 days after IRE, and findings were compared with baseline values by Student t test. Two animals each were euthanized at 1, 7, 14, and 28 days after IRE for histologic assessment of treatment effects. Quantitative histologic analysis of regeneration and healing of the ureteral wall was graded on a five-point scale.

RESULTS

IRE was successfully performed in all animals. Preservation of ureteral wall integrity was confirmed by the leakage-free passage of contrast medium in the treated ureter of all animals through the observation period. Ureteral strictures and associated renal pelvicaliceal dilation were observed in all animals by study days 7 (P = .005) and 14 (P = .007) and did not resolve by day 28. Urothelial recovery was observed in tissue samples from day 7, with progressive replacement of the tunica muscularis with granulation tissue. Despite extensive scarring of the tunica muscularis, full recovery of the urothelium was observed by day 28.

CONCLUSIONS

The normal porcine ureter retains lumen wall integrity and function following catheter-directed IRE. Scarring of the tunica muscularis in the treated ureter results in stricture formation and reduction of lumen patency.

Evaluation of carbon dioxide laser ablation combined with mitoxantrone and piroxicam treatment in dogs with transitional cell carcinoma

CASE DESCRIPTION

8 dogs that underwent carbon dioxide (CO2) laser ablation of transitional cell carcinoma in the bladder trigone and proximal portion of the urethra and were also treated with mitotranxone and piroxicam.

CLINICAL FINDINGS

Transitional cell carcinoma of the bladder frequently involves the trigone and urethra and can be difficult to manage surgically. Dogs underwent laser ablation of the primary tumor and were treated with mitoxantrone at a dosage of 5 mg/m2)every 3 weeks for 4 treatments. Piroxicam was given at a dosage of 0.3 mg/kg (0.14 mg/lb) once daily for the remaining life of the dog.

TREATMENT AND OUTCOME

Median and mean disease-free intervals were 200 and 280 days, respectively. Median and mean survival times were 299 and 411 days, respectively. Adverse treatment effects were observed in 2 dogs; signs included mild, self-limiting inappetance and lethargy. The procedure appeared to be well tolerated; all treated dogs had rapid resolution of clinical signs of disease of the lower portion of the urinary tract.

CLINICAL RELEVANCE

Although survival times achieved with CO2 laser ablation and treatment with mitoxantrone and piroxicam were similar to survival times associated with chemotherapy alone, resolution of clinical signs was better with the combined treatment.

Use of the holmium:YAG laser in urology

The tissue effects of a holmium:YAG (Ho:YAG) laser operating at a wavelength of 2.1 mu with a maximum power of 15 watts (W) and 10 different energy-pulse settings was systematically evaluated on kidney, bladder, prostate, ureteral, and vasal tissue in the dog. In addition, various urologic surgical procedures (partial nephrectomy, transurethral laser incision of the prostate, and laser-assisted vasovasostomy) were performed in the dog, and a laparoscopic pelvic lymph node dissection was carried out in a pig. Although the Ho:YAG laser has a strong affinity for water, precise tissue ablation was achieved in both the contact and non-contact mode when used endoscopically in a fluid medium to ablate prostatic and vesical tissue. Using the usual parameters for tissue destruction (blanching without charring), the depth of thermal injury in the bladder and ureter was kept superficial. In performing partial nephrectomies, a 2-fold reduction in the zone of coagulative necrosis was demonstrated compared to the use of the continuous wave Neodymium:YAG laser (Nd:YAG). When used through the laparoscope, the Ho:YAG laser provided precise cutting and, combined with electrocautery, allowed the dissection to proceed quickly and smoothly. Hemostatic control was adequate in all surgical procedures. Although the results of these investigations are preliminary, our initial experience with the Ho:YAG laser has been favorable and warrants further investigations.

Regeneration of the canine urinary bladder mucosa after complete surgical denudation

To study the site of origin of epithelial regeneration in the urinary bladder after surgical denudation, we completely obliterated the bladder mucosa in 17 dogs, using the neodymium: YAG laser. Bladder-mapping studies showed that the regenerating cells arose from the epithelium of the terminal ureters and urethra. Experimental construction of isolated bladder pouches confirmed these findings and demonstrated that urine flow was not essential for reepithelialization. These results are relevant to the treatment of patients with multifocal carcinoma in situ of the bladder. Although the entire bladder can be denuded successfully, the studies demonstrate that the procedure might fail if the sources of epithelial regrowth, the distal ureters and urethra, contain untreated carcinoma in situ.

Laser photoirradiation of the canine ureteral orifice: comparison between contact and noncontact techniques

We studied the long-term effects of Nd:YAG laser photoirradiation in 17 canine ureteral orifices, comparing results of the contact and noncontact (free-fiber) techniques. The noncontact technique damaged four of eight ureters, causing ureteral obstruction with significant hydronephrosis in three and reflux in one. The amount of energy used correlated with the subsequent appearance of ureteral obstruction; obstruction developed in both cases when 3,000 and 3,300 joules were used but in only one of five cases when less than 2,300 joules were used. In contrast, the contact technique, using 350-800 joules, caused no hydronephrosis and only one case of reflux. Since these animal studies clearly document that the Nd:YAG laser may significantly damage the ureter, particularly when the noncontact technique is used, we recommend that the surgeon consider the contact technique to reduce the risk of ureteral damage and use the smallest amount of energy required for adequate tumor eradication when treating tumors in or near the ureteral orifice.