Purpose: Treatment of urethral strictures is a major challenge in urology. For investigation of different treatment
methods an animal model was developed by reproducible induction of urethral strictures in rabbits to mimic the human
clinical situation. By means of this model the potential of endoluminal LDR brachytherapy using β-irradiation as
prophylaxis of recurrent urethral strictures investigated.
Material and Methods: A circumferential urethral stricture was induced by energy deposition using laser light
application (wavelength λ=1470 nm, 10 W, 10 s, applied energy 100 J) in the posterior urethra of anaesthetized New
Zealand White male rabbits. The radial light emitting fiber was introduced by means of a children resectoscope (14F).
The grade of urethral stricture was evaluated in 18 rabbits using videourethroscopy and urethrography at day 28 after
An innovative catheter was developed based on a β-irradiation emitting foil containing 32P, which was wrapped around
the application system. Two main groups (each n=18) were separated. The "internal urethrotomy group" received after
28days of stricture induction immediately after surgical urethrotomy of the stricture the radioactive catheter for one week
in a randomized, controlled and blinded manner. There were 3 subgroups with 6 animals each receiving 0 Gy, 15 Gy and
30 Gy. In contrast animals from the “De Nuovo group” received directly after the stricture induction (day 0) the
radioactive catheter also for the duration of one week divided into the same dose subgroups. In order to determine the
radiation tolerance of the urethral mucosa, additional animals without any stricture induction received a radioactive
catheter applying a total dose of 30 Gy (n=2) and 15 Gy (n=1). Cystourethrography and endoscopic examination of
urethra were performed on all operation days for monitoring treatment progress. Based on these investigation a
classification of the stricture size was performed and documented for correlation. At further 28 days after catheter
removal the animals were euthanasized and the urethra tissue was harvested. Histological examination of tissue with
assessment of radiation damage, fibrotic and inflammatory changes were performed. After deblinding histological
finding were correlated with the applied dose.
Results: All animals developed a stricture, while 15/18 (83,3%) showed a significant, high grade stricture with more
than 90% lumen narrowing. Histopathological examination including evaluation of urethral inflammation, fibrosis and
collagen content were investigated in additional 6 rabbits confirming the former findings. No rabbits died prematurely
during the study.
The experiments showed that the procedure of the application of radioactive catheter was safe without any problems in
contamination and protection handling. The combination of internal urethrotomy and LDR-brachytherapy results in a
stricture free rate of 66.7% in the 15-Gy group, compared with only 33.3% among animals from the 0- and 30-Gy
groups. Furthermore histological classification of inflammation and fibrosis of 0 Gy and 15 Gy showed similar extent.
Conclusion: This new method of laser induced urethral stricture was very efficient and showed a high reproducibility,
thus being useful for studying stenosis treatments. The experiments showed that application of local β-irradiation by
means of radioactive catheters modulated the stenosis development. This kind of LDR-brachytherapy shows potential for
prophylaxis of urethral stricture. As this was an animal pilot experiment a clinical dose response study is needed.
<strong>Introduction: </strong>Ureteric stenting is a commonly used endourologic procedure for temporary and long-term drainage of an obstructed upper urinary tract. The indication for ureteric stenting is obstruction due to intrinsic (intraureteral stones, strictures, or tumors) or extrinsic (for example compressing pelvic or retroperitoneal mass) causes. Despite the fact that stents do certainly have proven benefits in all fields of urology, there are potential morbidities. The most common problem of indwelling ureteral stents is infection. As foreign body in the urinary system, stents act as a nidus for bacteria colonization, crystallization and encrustation. Bacteria induced biofilm formation predisposes for the crystallization of lithogenic salts, such as calcium-phosphate, calcium-oxalate, magnesium-phosphate on the surface initiating stent encrustation. It was the objective of this study to evaluate whether optical coherence tomography (OCT) using both the surface and the endoluminal technique is feasible to investigate the locations and degree of encrustation process in clinically used ureteral stents. <strong>Patients and methods:</strong> After removal from patients, fourteen polyurethane JJ stents were investigated. A fresh JJ served as a control. The external surfaces were examined using an endoscopic surface OCT whereas the intraluminal surfaces were investigated by an endoluminal radial OCT device. The focus was on detection of encrustation or crystalline sedimentation. <strong>Results:</strong> In 12 female and 2 male patients, the median indwelling time of the ureteral catheter was 100 days (range 19- 217). Using the endoluminal OCT, the size and grade of intraluminal encrustation could be expressed as a percentage relating to the open lumen of the reference stent. The maximum encrustation observed resulted in a remaining unrestricted lumen of 15-35% compared to the reference. The luminal reduction caused by encrustation was significantly higher at the proximal end of the ureteral stent as compared to its distal part. The extraluminal OCT-investigations facilitated the characterization of extraluminal encrustation. <strong>Conclusion:</strong> OCT techniques were feasible and facilitated the detection of encrustation of double pigtail catheters on both the extra and intra luminal surface. Quantitative expression of the degree of intraluminal encrustation could be achieved, with the most dense and thickened occurrence of intraluminal incrustation in the upper curl of the JJ stent.
Introduction: Different laser-systems are currently used for stone fragmentation in the upper urinary tract. The aim of our study was to evaluate probe velocity and displacement, retropulsion and fragmentation characteristics two novel devices the electromechanically driven EMS LithoBreaker® (EMS Medical), and of the CO2 cartridge driven LMA StoneBreaker® (Cook Urological) in vitro test models.Testing of the LithoBreaker® included additionally two different cushion guides (harder, softer) to assess the effect of the damper properties on the impulse characteristics. Patients and methods: Maximum probe velocities and displacements were measured using high-speed photography at a resolution of 100.000 frames per second. Repulsion testing was conducted through a 7.5 Fr ureteroscope in an underwater set-up. The probes were projected against a non-frangible led mass placed in a 15 Fr horizontally mounted silicone tube as an <i>in-vitro</i> model of the ureter. Repulsion was determined by measuring the distance the lead mass (0.98g) was displaced. Fragmentation efficiency was assessed by measuring the number of single shots required to break Bego Stone phantoms hard (15:3) and soft (15:6) with an average size of 7.5 mm x 5.5 mm placed on a metal mesh (edge length 3.15mm) into < 3 mm fragments. Mean and standard deviation were computed for all groups and statistical analysis was performed (student’s t-test). Results: The StoneBreaker® yielded the highest velocity of 22.0 ± 1.9 m/sec. followed by the LithoBreaker® assembled with the hard cushion guide of 14.2 ± 0.5 m/sec and the soft probe guide of 11.5 ±0.5 m/sec. accordingly. The maximum probe displacement for the StoneBreaker® was 1.04 mm and for the LithoBreaker® 0.9 mm and 1.1 mm (hard versus soft cushion guide). Repulsion produced using the 1mm probes showed no statistical differences between the devices. Using the 2mm probes, the hardness of the damper used significantly changed the repulsion behaviour of the LithoBreaker®. Using the 1mm probe, the amount of single shots for fragmentation of soft Bego Stones was significantly higher for the LithoBreaker® with soft cushion guide: mean 31.5 ± 11.31 and hard cushion guide: mean 21.5 ± 5.29 compared to the StoneBreaker®: mean 11.2 ± 2.65. Fragmentation efficiency for the hard Bego Stones showed similar statistically significant results. Conclusion: The electromechanic LithoBreaker® and the pneumatic Stonebreaker® were shown to be effective in cracking stone phantoms with relatively low number of pulses. Fragmentation characteristics improved substantially with the higher hardness of the cushion support higher velocity equals higher fragmentation performance of the LithoBreaker®. Repulsion produced were at comparable levels. More testing is required to more detailed information on impulse frequency and capacity for stone clearance time to be used in clinical practice.
Bladder cancer (BC) is among the most expensive oncological diseases. Any improvement in diagnosis or therapy
carries a high potential for reducing costs. Fluorescence cystoscopy relies on a selective formation of Protoporphyrin IX
(PpIX) or more general photoactive porphyrins (PAP) in malignant urothelium upon instillation of 5-aminolevulinic acid
(5-ALA) or its hexyl-derivative h-ALA. Fluorescence cystoscopy equipment has been developed with the aim to
compensate for the undesired distortion caused by the tissue optical properties by displaying the red fluorescence
simultaneously with the backscattered blue light. Many clinical studies proved a high sensitivity in detecting flat
carcinoma in situ and small papillary malignant tumours. As a result, recurrence rates were significantly decreased in
most studies. The limitation lies in a low specificity, caused by false positive findings at inflamed bladder wall. Optical
coherence tomography (OCT) is currently being investigated as a promising tool to overcome this limitation.
H-ALA-PDT (8 or 16 mM h-ALA in 50 ml instillation for 1-2 h, white light source, catheter applicator) has recently
been investigated in a phase I study. 17 patients were applied 100 J/cm<sup>2</sup> (3 patients received incrementing doses of 25 -
50 - 100 J/cm<sup>2</sup>) during approx. 1 hour irradiation time in 3 sessions, 6 weeks apart. PDT was performed without any
technical complications. Complete photobleaching of the PpIX-fluorescence, as intended, could be achieved in 43 of 45
PDT-sessions receiving 100 J/cm<sup>2</sup>. The most prominent side effects were postoperative urgency and bladder pain, all
symptoms being more severe after 16 mM h-ALA. Preliminary evaluation shows complete response assessed at 3
months after the third PDT-session (i.e. 6 months after first treatment) in 9 of 12 patients. 2 of these patients were free of
recurrence until final follow-up at 84 weeks.
Objectives: In this study, clinically available pulsed laser systems emitting either in the infrared (IR) - or visible (VIS)
spectral region were compared in a standardized manner with respect to their impact on phantom stones in an
underwater laboratory set-up.
Methods: There were three pulsed laser systems emitting light either in the IR (λ=2100nm: Ho: YAG-laser) or VIS
(λ=532nm/1064nm: FREDDY-laser and 598nm: FLPD-laser) spectral range available for this investigation. After
determination of the ablation threshold different fragmentation rates were determined in relation to the fluence
(depending on pulse energy and fiber diameter) using artificial stones.
Results: The threshold value of the laser pulse energy to induce an ablation of artificial stones induced by the different
laser systems showed that even the lowest laser settings induced significant ablation with no regards to the repetition
rate and fiber diameter. The VIS-lasers showed higher fragmentation rates than the IR-lasers.
Conclusions: VIS-lasers are solely useful for laser induced shockwave lithotripsy, while IR-lasers are also in use for
other clinical applications (e.g. coagulation and ablation). Investigations on artificial stone fragmentation are useful to
compare clinical laser parameter settings but can partially be transferred to clinically urinary stone fragmentation.