Experimental utilization of the holmium laser in a model of ureteroscopic lithotripsy: energy analysis

The Feasibility of Pop-Dusting Using High-Power Laser (2 J × 50 Hz) in Retrograde Intrarenal Surgery for Renal Stones: Retrospective Single-Center Experience

Objective: Recently, retrograde intrarenal surgery (RIRS) using laser lithotripsy has become popular. However, the optimal laser energy setting for pop-dusting has not been established. In this study, we report our experiences of RIRS using the high-power (up to 100 W) pop-dusting (HPPD) technique. Methods: This study retrospectively assessed 82 cases with RIRS using HPPD. Patients who underwent abdominal CT or mercaptoacetyltriglycine (MAG3) diuretic renal scan at 3 months postoperatively were included in this study. Patient and stone characteristics and perioperative and postoperative outcomes were evaluated. Results: The average number of renal stones was 3.67 ± 4.11, and the average length of the largest stones was 13.30 ± 6.41 mm. The mean Hounsfield units was 959.99 ± 384.73. The operation time was 58.10 ± 26.67 minutes. The mean HPPD time was 11.93 ± 9.48 minutes, with settings of 1.97 ± 0.25 J and 48.78 ± 3.29 Hz. The stone-free rate was 89%. The mean hospital stay was 1.68 ± 1.29 days. Pelvicaliceal and ureter injuries were observed in 9.8% and 32.9% of the study population, respectively. However, there was no transfusion, subcapsular hematoma, persistent urinary leakage, ureteral or infundibular stricture, or renal functional deterioration. There was transient postoperative fever in 12.2% of the study population. Conclusions: HPPD could be performed safely during RIRS for renal stones without significant complications such as collecting system injury or bleeding. High-power laser mode (up to 100 W) can be a safe and effective choice for pop-dusting during RIRS, especially for large and hard stones.

IN VITRO COMPARISON OF STONE RETROPULSION AND FRAGMENTATION OF THE FREQUENCY DOUBLED, DOUBLE PULSE ND:YAG LASER AND THE HOLMIUM:YAG LASER

PURPOSE

The frequency doubled, double pulse Nd:YAG (FREDDY) laser (World of Medicine, Berlin, Germany) functions through the generation of a plasma bubble. Upon bubble collapse a mechanical shock wave is generated, causing stone fragmentation. This mechanism of action is in contrast to the holmium laser, which cause stone destruction by vaporization. Observed clinical stone retropulsion and fragmentation with the FREDDY and holmium lasers has prompted a series of in vitro experiments designed to compare laser induced retropulsion and fragmentation with those of a holmium laser and pneumatic lithotrite.

MATERIALS AND METHODS

For retropulsion a hands-off underwater laboratory setup, including a horizontally oriented silicone tube 1.3 cm in diameter and a holder to keep the stone phantom in contact with the quartz laser fiber or pneumatic probe, was used. Previously weighed, cylindrical Bego stone phantoms (Bego USA, Smithfield, Rhode Island) were placed in the apparatus. Stone fragmentation was performed with the FREDDY or holmium laser, or the pneumatic lithotripter. The FREDDY and holmium lasers were tested at similar pulse energy and frequency settings. As a standard for comparison, a pneumatic lithotrite was tested with a semirigid probe and single pulse settings of 100, 200 and 300 kPa. Stone phantoms underwent 30 shocks per setting. Mean net retropulsion, defined as the final resting point of the stone, as determined by direct measurement, was recorded for each setting. For fragmentation plaster of Paris stone phantoms of known weights were used to compare the fragmentation ability of each laser. Stones phantoms were placed in a hands-off underwater setup, consisting of an inverted silicon syringe and holder immersed in tap water. The laser fiber (365 microm for the holmium and 280 microm for the FREDDY) was placed through the tip of the syringe in contact with the stone phantom. A total of 24 stones were divided into 4 groups of 6 per group. Two groups were fragmented with the FREDDY laser at 300 and 400 J total energy. The other 2 groups were fragmented using the holmium laser at 300 and 480 J total energy. Fragmentation efficiency was determined as percent weight loss.

RESULTS

For retropulsion at 160 mJ the FREDDY laser caused stone retropulsion to a mean distance of 7.6, 8.1 and 6.8 cm at settings of 5, 10 and 15 Hz, respectively. At 0.8 J the holmium laser retropulsed the stone to a mean distance of 3.3 and 4.9 cm at settings of 5 and 10 Hz, respectively. The pneumatic device caused stone retropulsion a mean distance of 8.5, 9.9 and 13.8 cm at pressure settings of 100, 200 and 300 kPa, respectively. The FREDDY laser generally caused less retropulsion than the pneumatic device, although this difference was only significant at the highest pneumatic lithoclast setting (p <0.05). At clinically relevant settings the FREDDY laser caused significantly more retropulsion than the holmium laser (p <0.05). For fragmentation at total energy settings of 300 and 400 J the FREDDY laser resulted in 44.9% and 86.8% weight loss, respectively (p <0.05). At settings of 300 and 480 J the holmium:YAG laser resulted in 3.3% and 7.1% weight loss, respectively (p <0.05).

CONCLUSIONS

At lower frequency settings stone retropulsion was significantly greater with the FREDDY laser compared with the holmium laser. However, retropulsion was significantly less than that caused by the pneumatic lithotripter at all settings. Therefore, we recommend the use of an occlusive device, such as the Stone Cone (Boston Scientific, Natick, Massachusetts) proximal to the calculus during intracorporeal ureteral lithotripsy and in the ureteropelvic junction during percutaneous laser nephrostolithotomy. In vitro stone fragmentation was significantly greater with the FREDDY laser than with the holmium:YAG laser, suggesting that the FREDDY may offer a low cost alternative to the holmium:YAG laser lithotrite in select patients.

Indwelling ureteral stents: evaluation of quality of life to aid outcome analysis

BACKGROUND

Ureteral stents cause various side effects. We have evaluated health-related quality of life (HRQoL) in patients with stents using validated questionnaires and developed a new stent symptom (intervention)-specific questionnaire (SSQ).

PATIENTS AND METHODS

Along with structured literature review and in-depth interviews, prospective sub-studies were carried out using generic (SF-36 [N = 30], EuroQol [N = 40], and Functional Status Questionnaire FSQ [N = 20]) and symptom-specific (IPSS [N = 30] and International Continence Society ICS [N = 30]) questionnaires both with a stent in situ and after removal. The results of these studies formed the foundation for a new SSQ that was pilot tested (N = 10) and field tested (N = 20) in order to develop a final draft of the questionnaire that is formally validated.

RESULTS

The qualitative research identified a range of problems. Urinary symptoms, pain, work performance, and general health were the most important. Most patients (80%) experienced bothersome urinary symptoms and stent-related pain. Storage symptoms and incontinence were significant urinary symptoms affecting quality of life. As many as 40% of patients experienced sexual dysfunction. The stent had a significant impact on patients' general health. None of the existing measures evaluated the complete impact. The SSQ includes five sections covering urinary symptoms, pain, sexual matters, general health, and work performance. The preliminary results showed it to be valid, reliable (alpha > 0.7) and responsive to the change in scores (p < 0.05) after stent removal.

CONCLUSIONS

Indwelling ureteral stents are associated with significant morbidity, resulting in a reduced HRQoL in 80% of patients. The SSQ is a reliable intervention-specific instrument that would be useful as an outcome measure to evaluate the impact of stents.

Update on contact lithotripsy

Despite the development of extracorporeal shockwave lithotripsy, endoscopic stone removal, with or without intracorporeal lithotripsy, is still an effective minimally invasive alternative for special indications. There is no defined all-purpose lithotripsy procedure for contact lithotripsy. The choice of the lithotripsy procedure for endoscopic stone disintegration depends on a number of different factors, the main one being stone localization. Small calibre, flexible probes (electrohydraulic, pneumatic, laser) are especially appropriate for ureterorenoscopy, but the speed of stone disintegration is a limiting factor. In contrast, large calibre rigid probes (ultrasound) are clearly more effective, but are unsuitable in size for flexible ureterorenoscopy. This indicates that the type and size of the endoscope decisively influences the choice of devices for endoscopic stone disintegration. Additional inhibiting factors are the flexibility or the rigidity of the instrument and the diameter of the working channel. It must be noted that total costs are not only calculated on the purchase of the equipment, but must also cover disposable materials.

Microwave thermotherapy: historical overview

The application of heat with curative aim is an old and very well-known principle in medicine. A review of the history of heat use in the treatment of prostatic disease is presented. The article is based on bibliographic research (MEDLINE Search and PubMed) and focuses on treatment of benign prostatic hyperplasia (BPH) since the first clinical documentation of transrectal hyperthermia for this condition. Then, in a chronological sequence, not only the evolution toward thermotherapy but also enhancements of the latest techniques are presented. The new advances in the field of patient selection, indications, and outcome predictors, as well as new trends in treatment are briefly considered.