Biomedical subjects
Publications and source records attributed to K Planz.
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.
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.
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.
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.
A total of 91 patients were treated for upper tract urothelial tumors between 1981 and 1991. Preoperative computed tomography (CT) scans and nephroureterectomy for treatment of transitional cell carcinoma were performed in 26 patients. At pathological examination, 28 tumors were diagnosed of which 19 were in the renal pelvis and 7 were in the ureter. Intravenous pyelogram, retrograde and antegrade pyelogram detected 26 of 28 tumors (93%). CT detected 24 of 28 tumors (86%). However, CT is still the best current method for staging of upper urinary tract urothelial tumors, although staging was correct in only 5 of 9 T3 and T4 tumors.
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A Siemens Lithostar shock wave system was modified and investigated clinically. The modified system yields increased focal pressure and energy density. The first clinical experience in renal calculi shows a significant reduction in shock wave numbers per treatment. Higher energy output enables better treatment results for difficult stones such as staghorn and infections calculi. Despite the higher energy output more than 90% of treatments could be performed without anesthesia or analgesia. No significant side effects could be detected. The service life of the modified shock wave system increased by a factor of two.
The antireflux operation according to Lich-Grégoir (L-G) poses no particular technical problems and involves no major surgical stress to the patient. Of its intraoperative complications lesions to the bladder mucosa have to be considered in the first place. Its postoperative complications calling for reoperation comprise recurrence of reflux, ureteral stricture and ureteral fistula. Results of the Lich-Grégoir operation performed in 176 instances are reported. The complication rate was 4.5 per cent. The complications are commented upon, and the types and time of reoperations are discussed.
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