Preventing Migration of Stones During Fragmentation with Thermosensitive Polymer

In vivo evaluation of a reverse thermosensitive polymer for ureteroscopy with laser lithotripsy: porcine model

PURPOSE

To evaluate the effects of a reverse thermosensitive polymer during ureteroscopy with laser lithotripsy in an in vivo porcine model.

MATERIALS AND METHODS

Six pigs underwent general anesthesia followed by bilateral ureteroscopy with laser lithotripsy of stone phantoms while measuring intrapelvic renal pressures through bilateral nephrostomy tubes. The procedures were performed in one ureter with the reverse thermosensitive polymer and in the contralateral, control ureter without the reverse thermosensitive polymer. Stone migration lengths, operative times, laser times, laser energy usage, intrapelvic pressures, and postnecropsy histologic examinations of the ureters were compared between the two groups.

RESULTS

Bilateral ureteroscopy with lithotripsy was successfully performed in five of six pigs. In one pig, only the unilateral control was performed, because the ureter was too narrow to complete the contralateral side. The mean laser time was 12.8 minutes shorter with the use of the reverse thermosensitive polymer group than in the controls (P=0.021). The procedure time, laser energy usage, and retropulsion length was shorter in the reverse thermosensitive polymer group, but did not reach significance. Between the two groups, there was no difference in mean renal pelvic pressures, peak renal pelvic pressures, or postprocedure histologic examinations of the ureters.

CONCLUSIONS

The use of a reverse thermosensitive polymer during ureteroscopy with lithotripsy may have greater advantages beyond preventing stone retropulsion. Here, the use of a reverse thermosensitive polymer during ureteroscopy with lithotripsy resulted in a significant decrease in laser times. Further clinical investigations could further delineate the advantages of using a reverse thermosensitive polymer during intracorporeal lithotripsy.

Increasing dwell time of mitomycin C in the upper tract with a reverse thermosensitive polymer

Abstract Background and Purpose: Topical chemotherapy for urothelial cancer is dependent on adequate contact time of the chemotherapeutic agent with the urothelium. To date, there has not been a reliable method of maintaining this contact for renal or ureteral urothelial carcinoma. We evaluated the safety and feasibility of using a reverse thermosensitive polymer to improve dwell times of mitomycin C (MMC) in the upper tract.

MATERIALS AND METHODS

Using a porcine model, four animals were treated ureteroscopically with both upper urinary tracts receiving MMC mixed with iodinated contrast. One additional animal received MMC percutaneously. The treatment side had ureteral outflow blocked with a reverse thermosensitive polymer plug. MMC dwell time was monitored fluoroscopically and intrarenal pressures measured. Two animals were euthanized immediately, and three animals were euthanized 5 days afterward.

RESULTS

In control kidneys, drainage occurred at a mean of 5.3±0.58 minutes. Intrarenal pressures stayed fairly stable: 9.7±14.0 cm H20. In treatment kidneys, dwell time was extended to 60 minutes, when the polymer was washed out. Intrarenal pressures in the treatment kidneys peaked at 75.0±14.7 cm H20 and reached steady state at 60 cm H20. Pressures normalized after washout of the polymer with cool saline. Average washout time was 11.8±9.6 minutes. No histopathologic differences were seen between the control and treatment kidneys, or with immediate compared with delayed euthanasia.

CONCLUSIONS

A reverse thermosensitive polymer can retain MMC in the upper urinary tract and appears to be safe from our examination of intrarenal pressures and histopathology. This technique may improve the efficacy of topical chemotherapy in the management of upper tract urothelial carcinoma.