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We detected a special plastic, which is stable in an acid environment and dissolvable in a basic one. Our preliminary in-vitro results show that the tested material therefore seems principally designed for developing biodissolvable stents for temporary urinary diversion out of the upper urinary tract. Stableness and dissolution could be steered by manipulating the pH.

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The disadvantages of high flexible endoureteral stents (DJ) in case of tumorinduced extrinsic ureteral compression are due to an insufficient vertical stability of the used stents leading to stent-compression and consecutive hydro- or pyonephrosis. The new developed tumor-stent used in case of tumor-induced ureteral compression is available from 6 to 8 French in diameter and 24 to 32 cm in length. The corpus consists of a combination of high-stability plastics but is of sufficient elasticity in length. Both ends consist of extremely elastic J-parts guaranteeing an exact fixation. As against common DJ's with the same outside-diameter the new stent has a comparable interior diameter and compared to used "old" tumor stents promises a higher interior flow in case of extrinsic diseases. The application can be undertaken in well-known technique, needs no special instrumentation and no learning-curve. To date 52 stents at our urologic departments were placed without any problems, the latest remaining for 15 months. Tumor-induced compression or a higher rate of encrustation could not be seen. All patients tolerated these stents well. In our opinion the new stabilized endoureteral stent can be seen as a better solution instead of percutaneous nephrostomy or frequent stent changing in patients with tumor induced extrinsic ureteral compression.

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Internal ureteral stents are widely used in urologic practice for temporary urinary diversion, but all double-J catheters to date exhibit the same disadvantage; that is, they have to be removed endoscopically, necessitating further intervention. We tested different materials (designated G100X-15xLB and G100X-20xLB) to develop a biodegradable (biodissolvable) endoureteral stent that can be held in place without functional loss yet could be dissolved by changing the environment. The principle of the biochemical background is based on the physiological milieu of the urine. The plastics tested are stable in acidic and dissolve in alkaline conditions. In a first step, specimens of two polymers were placed in artificial urine of different pH over a period of 60 days and monitored for integrity (solution trial). In a second step, artificial urine was set in motion (744 mL/24 hours) an infusion pump (Volumed microVP 5000; Fresenius AG, Bad Homburg vdH, Germany) through an infusion set in which a 30-cm piece of the materials to test had been placed (ureter model). Below the inserted specimen, the lumen of the infusion tube was minimized to make obstruction by fragments more possible. In the solution trial, all specimens remained stable under physiologic conditions (pH 5.2) over a period of at least 30 days. The specimens dissolved completely when the pH was adjusted to an alkaline one (pH 7.9). In the ureter model, with pH values of 7.9, all specimens were decomposed after 20 hours, and no occlusion of the model occurred. Using acidic artificial urine, the specimens remained stable with a smooth consistent surface. The dissolution was not a standard chemical one; the materials broke into microscopically small pieces, with fragments of G100X-20xLB being smaller than those of G100X-15xLB. Our first in vitro results show that the tested materials are suitable for further development of biodissolvable endoureteral stents, dissolution of which can be steered by changing the urinary pH.

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The disadvantages of highly flexible endoureteral (double J) stents in the face of tumor-induced extrinsic ureteral compression are a consequence of insufficient cross-sectional stability, leading to stent compression and thus to hydronephrosis or pyonephrosis. The newly developed tumor stent, which is used in cases of tumor-induced ureteral compression, is available in sizes from 6F to 8F in diameter and 24 to 32 cm in length. The shaft consists of a combination of high-stability plastics that presents sufficient elasticity in length. Both ends are made of extremely elastic J parts, guaranteeing stable fixation. Compared with common double-J stents with the same outside diameter, the tumor stent possesses a comparable interior diameter and compared with available stents promises sufficient interior flow in the face of extrinsic diseases. The application can be undertaken using well-known endoscopic techniques, needs no special instrumentation, and entails no learning curve. To date, 49 stents were placed at our urologic departments without any problems, the latest stent remaining for 15 months. Tumor-induced compression or a higher rate of encrustation were not seen. All patients tolerated these stents well. In our opinion, the new stabilized endoureteral stent can be seen as a better solution than percutaneous nephrostomy or frequent stent changing to tumor-induced extrinsic ureteral compression.

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OBJECTIVES: To develop and test materials that may be useful in the design and further development of biodegradable ureteric stents. MATERIALS AND METHODS: Specimens of two plastics were placed in artificial urine of different pH for 30 days to examine the degree of dissolution of the plastic in alkaline and the stability in acidic conditions. RESULTS: The specimens remained stable in the artificial urine at pH < 7.0 for 30 days and dissolved completely at a pH > or = 7 within 48 h. CONCLUSION: Plastics can be designed which may be useful in the further development of biodegradable ureteric stents. The rate of dissolution could be changed by influencing urinary pH.

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The MODULITH SL20 combines on-line ultrasound and optional X-ray in series. In addition to highly simplified patient positioning and the possibility of handling the machine as a multipurpose lithotripter for disintegration of urinary-, gallbladder and bile duct stones and for treatment of pancreatic concrements this appliance can be used in cases of sialolithiasis and as a workplace for all urological purposes, so that the design is very modern. As the energy level in f2 can be extremely high, a disintegration rate of about was achieved for 70% ureteral stones in the middle and distal sections of the ureter. However, this good disintegration rate was not achieved for ureteral stones lying in the upper ureter or in cases of nephrolithiasis treated with a prototype of the machine. In our opinion, this reflects a problem with nonexistent on-line X-ray stone localization, but an overall disintegration rate of about 77% in preselected patients (1.8 stones/patient) confirms that this is a highly sophisticated and powerful machine.

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In a prospective study, results of the extracorporeal shock wave lithotripsy of salivary stones were evaluated. The study was performed with the currently available technical possibilities of electromagnetic systems to get indication criteria for this procedure. Using the Modulith SL 20-lithotripter of Storz Medical AG, 33 concrements in 25 patients were treated in 89 lithotripsy sections. The stone sizes, localized by ultrasound, ranged from 3 to 13 mm diameter (phi 6.9 mm). After application of local anaesthesia, per session on an average 1300 shock waves with raising energy levels were applied, the succession of shocks fixed to 1 MHz. With the help of ultrasound localisation, a therapeutic success with complete emission of the concrement or an adequate disintegration of these stones could be achieved in 82% of the parotid gland stones (n = 11) and in 14% of the submandibular gland stones (n = 22). Since the unhampered functioning of these salivary glands is an inevitable pre-condition for the spontaneous emission of the disintegrated fragments, the status of function of salivary glands should be established by a scintigraphy before performing the ESWL. Even though complete emission of the stone could be achieved in only 4 patients, all patients were clinically free of symptoms after the treatment. In 3 of 25 patients, discrete bleeding of a passing nature occurred coming from the salivary duct. In 2 patients, formation of haematoma of varying dimensions could be visualized by ultrasound. 3 patients showed petechial skin bleeding. The tinnitus aurium which affected one patient eased after 3 days. In our patients collective a facial nerve damage did not occur.2+ longterm prognosis after this procedure.

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