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Biomedical subjects

J Rassweiler

Publications and source records attributed to J Rassweiler.

At least 55 records · Page 3Linked to original sources
PubMed1994

The isolated perfused kidney of the pig: new model to evaluate shock wave-induced lesions.

Little is known about the mechanisms and determining factors of shock wave-induced kidney trauma. After classification of the renal lesion in a canine model, we attempted to establish an ex vivo model using the isolated kidney of the pig perfused by Tyrode's solution under physiologic conditions. After shock wave application on the Modulith SL 20, vessel lesions were evaluated by microangiography to determine the size and frequency of dye extravasation in the different areas of the organ. Variation of the focus localization caused different patterns of lesions that characterized the pathway of the shock wave. In particular, constant petechial extravasation in the cortex was observed. The generator voltage correlated with the diameter and the frequency of the lesion area. The number of shock waves primarily affected the incidence of vessel rupture in the regions adjacent to the focal zone. Light microscopy revealed dose-dependent necrosis of tubular cells up to gap-like parenchymal defects. Even after application of the minimal shock wave doses, electron microscopy demonstrated vacuolization of tubular cells in the shock wave focus. Traumatic junctions between capillaries and the tubulur system can explain clinically observed macrohematuria without renal hematomas. With this model, it was possible to evaluate localization and dose dependence of shock wave-induced kidney trauma with high sensitivity and reproducibility. Further advantages of the model were easy availability and the fact that studies on living animals were not necessary. Therefore, standardization and comparison of different lithotripters becomes possible.

Angiography↗
PubMed1994

Spiral-reinforced ureteral stent: an alternative for internal urinary diversion.

Internal urinary diversion of chronic ureteral obstruction is not sufficient in as many as 60% of patients because of tumor compression, catheter kinking, or a small stent lumen. To prevent such problems, we developed a new ureteral stent that is stable in form in spite of a large lumen. This catheter is a thin polyurethane tube supported by a built-in metal spiral wire. We have attempted to use this stent in 16 cases of chronic ureteral obstruction. Stent placement was successful in 14. Other than urinary tract infection in two patients, bladder urgency in one, and stent dislocation in another, there were no complications. Hydronephrosis disappeared soon after stent application in 12 of the 14 patients, and in the remaining two, hydronephrosis was decreased but not totally eliminated. Catheters were left in place for an average of 6.5 weeks (range 2.5-8.5 weeks). A change of catheter because of blockage was necessary in only one patient. This spiral-reinforced stent enables better internal urinary drainage, especially in cases of malignant ureteral obstruction.

Equipment Design↗
PubMed1994

Histomorphologic and ultrastructural findings of shockwave-induced lesions in the isolated perfused kidney of the pig.

The aim of this investigation was the development of an easily reproducible model with which to evaluate shockwave-induced renal tissue damage using light and electron microscopy. Kidneys (n = 45) from freshly slaughtered pigs were perfused under physiologic conditions and treated with shockwaves at different doses (2-250 shockwaves; 12-20 kV) on the Modulith SL 20 lithotripter. The dose-dependent alterations in tissue structure were characterized by disintegration of tubular cells leading to circumscribed gap-like defects resulting from reticular fiber disruptions. Even after low shockwave doses, cellular and subcellular alterations could be observed. Our findings in this ex vivo model verify the development of considerable strictly localized, dose-dependent shockwave-induced damage of the renal parenchyma. On morphologic grounds, we cannot confirm a primary lesion or rupture of blood vessel walls as the cause of the shockwave lesions. The destruction of tubular cells in combination with disruption of peritubular and pericapillary reticular fiber coats results in capillarotubular leaks, which can explain even severe transitory macrohematuria after clinical shockwave lithotripsy without renal hematoma formation.

Animals↗
PubMed1994

Antegrade-retrograde urethrotomy for treatment of severe strictures of the urethra: experience and literature review.

In cases of urethral stricture that are nonpassable when using conventional internal urethrotomy, open urethroplasty can be avoided by performing combined antegrade-retrograde urethrotomy (ARUT). A rigid cystoscope is guided through a dilated suprapubic cystostomy channel toward the stricture in the membranous or bulbar urethra. A urethrotome is inserted in retrograde fashion, and the "cut to the light" procedure is performed. Using the ARUT method, realignment was achieved in nine patients; four of whom had strictures induced by trauma or urethritis and five of which were the result of previous transurethral management. Recurrent stricture in four of seven cases necessitated further urethrotomy. There was no recurrence in five of seven patients for at least 5 months subsequent to the last treatment. All patients were spared open surgery. The antegrade-retrograde technique was described in 1978, but to date, only 70 cases have been reported in the literature. The primary success rate is 25%. Successful retreatment following recurrence was observed in 65%. We recommend ARUT as a first-choice treatment for severe strictures of the bulbar and membranous urethra.

Adult↗
PubMed1994

Experimental studies for clinical standardization of transabdominal laparoscopic nephrectomy.

In keeping with the maxim that minimal invasiveness is the present working trend in most areas of surgery, we investigated the possibility of laparoscopically removing a diseased human kidney. Before any actual clinical attempt could be made in this direction, an experimental study was set up in order to determine the most beneficial methods and techniques which would guide us through our first clinical cases. This step-by-step training program consists of: (1) initial familiarization with different laparoscopic instruments, bimanual dissection, ligation and coagulation techniques, camera handling and trocar placement as well as organ retrieval systems using the lap simulator; (2) laparoscopic removal of the kidney and ureter of the pig either as short- or long-term study, and (3) laparoscopic simulation with the lap tent during open surgery.

Animals↗
PubMed1994

Role of human chorionic gonadotropin in patients with pure seminoma.

Human chorionic gonadotropin (beta-hCG) and alpha-fetoprotein (AFP) are widely established specific and sensitive tumor markers for nonseminomatous testicular cancer. In 106 patients with pure seminoma, a highly sensitive method detected beta-hCG both before and repeatedly during therapy. The low detection limit of the test (0.3 IU/l) coincided with the 95 percentile of a group of 60 healthy blood donors. Its 100 percentile of < 1.0 IU/l was applied as the upper limit of the normal range. In 30.2% of our patients with pure seminoma, elevated beta-hCG levels were noted prior to orchiectomy. The levels returned to normal in 76% of these patients thereafter, and in 34% after additional irradiation or chemotherapy. During an observation period of 2-84 months, all beta-hCG-positive patients were in complete remission. Prior to semicastration, 1 patient showed extremely high beta-hCG levels, while in another patient, beta-hCG and AFP were elevated simultaneously. In both cases, tumor marker levels did not seem to agree with the histology of 'pure seminoma' and rather suggested the presence of nonseminomatous tumor cells. Increased AFP levels contradict the presence of a pure seminoma and indicate a nonseminomatous testicular tumor. The same holds true for strongly elevated beta-hCG levels, whereas levels of up to 200 IU/l correlate with the diagnosis of pure seminoma.

Adult↗
PubMed1994

[Neoadjuvant chemotherapy of invasive bladder cancer].

Neoadjuvant chemotherapy is defined as cytotoxic treatment of an invasive carcinoma of the bladder. It is primarily suitable for a curative cystectomy with the aim of improving the therapeutic chances of the definitive treatment (i.e., cystectomy, radiotherapy) by devitalization of the primary tumor and effective control of micrometastases. Thus, one of the major goals is preoperative sterilization of the tumor (stage pT0) to avoid tumor cell seeding during surgery. Until now, the documented pathological complete response rate (CRp) after 2-4 cycles of polychemotherapy has ranged from 19 to 38% plus 3 to 23% of complete surgical response (CRs) with residual superficial bladder tumors in the cystectomy specimen. The survival rates following neoadjuvant polychemotherapy differ considerably between 54 and 82% independent of the definitive treatment (cystectomy, radiotherapy). However, the response to chemotherapy has a significant impact on survival: patients with major pathological response (CRp + CRs) yielded a 75-100% disease-free survival after 4 to 5 years in contrast to 20-22% for partial or non-responders. Future studies should investigate methods predicting the outcome of polychemotherapy (i.e., identifying mdr-chemoresistant tumors by detection of P170 glycoprotein in the TUR specimen) or improving the reliability of preoperative diagnosis (clinical = pathological complete response).

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

[Ureteral stent reinforced with a spiral--an alternative to internal drainage of urine].

Internal urinary diversion of chronic ureteral obstruction is not sufficient in up to 60% of the cases. Factors for this high failure rate are tumor compression, catheter kinking or a small stent lumen. To prevent such problems we have developed a new ureteral stent which is stable in form in spite of a large stent lumen. This catheter is made of a thin polyurethane tube which is supported by a built-in metallic spiral wire. We have used this stent in 16 cases of chronic ureteral obstruction. Stent placement was successful in 14 cases. Other than urinary tract infection in two cases, bladder urgency in one case and stent dislocation in another case there were no complications. Hydronephrosis disappeared soon after stent application in 12 out of 14 cases. In the remaining two cases hydronephrosis was decreased, but not totally eliminated. Catheters were left in place for an average of 6.5 weeks (2.5-8.5). A change of catheter due to catheter blockage was necessary only in one case. In conclusion, this spiral reinforced stent enables a better internal urinary drainage especially in cases of malignant ureteral obstruction.

Female↗
PubMed1994

Ureteral stone. Treatment using the Modulith SL 20 and Lithostar plus.

The treatment of ureteric calculi by extra-corporeal shock waves was found to have an 80% success rate by Mannheim authors, regardless of the site of the calculus. The authors compared two 3rd generation apparatuses: 1--the Siemens Lithostar Plus, in which waves are produced by a electromagnetic cylinder and focussed by a parabolic electromagnetic cylinder and focussed by a parabolic reflector: 2--the Storz Medical Modulith SL 10, in which waves produced by an electromagnetic coil are focussed by acoustic lenses. Both apparatuses are based upon image-intensification and ultrasonography concepts. No difference in efficacy was found between the two apparatuses. A second shock wave session was necessary in 16% of cases and some other type of additional treatment in 7% of cases.

Acoustics↗
PubMed1993

The recurrence rate of stones following ESWL.

With extracorporeal shockwave lithotripsy (ESWL) stone fragmentation and the potential creation of residual stones has become an integral part of the treatment strategy. Therefore true recurrence, regrowth and pseudo-recurrence determine the rate of new stone formation. In unselected series the overall recurrence rate after ESWL varies between 6% after 1 year and 20% after 4 years. The comparison between the recurrence rate after ESWL and the natural recurrence rate reveals that the results of ESWL are better than expected. Lithotripsy has no special effect on true stone recurrence, and even pseudo-recurrence is of minor clinical significance.

Follow-Up Studies↗
PubMed1993

Experimental basis of shockwave-induced renal trauma in the model of the canine kidney.

Using the new electromagnetic shockwave source of the Modulith SL 20 shockwave-induced renal trauma was evaluated by acute and chronic studies in the the canine kidney model. In a further study the electromagnetic shockwave source of the Lithostar Plus Overhead module was tested. Overall, 92 kidneys were exposed to shock waves coupled either by water bath (Modulith lab type) or by water cushion (Modulith prototype, Lithostar Overhead) under ultrasound localization. The generator voltage ranged between 11 and 21 kV, the number of impulses between 25 and 2500. After application of 1500/2500 shocks the extent of the renal lesion depended strictly on the applied generator voltage and was classified into 4 grades: Grade 0, no macroscopic trauma detectable (at 11-12 kV); grade 1, petechial medullary bleeding (at 13 kV); grade 2, cortical hematoma (at 14-16 kV); and grade 3, perirenal hematoma (17-20 kV). Whereas at low and medium energy levels the number of shocks played only a minor role, at maximal generator voltage (20 kV) even 25 impulses induced a grade 2 and 600 shocks a grade 3 lesion, emphasizing the importance of shockwave limitation in the upper energy range. In shockwave-induced renal trauma a vascular lesion was predominant and cellular necrosis was secondary. Coupling with a water cushion resulted in a 15%-20% decrease in the disintegrative and traumatic effect, which was compensated for by increasing the generator voltage by 2 kV. Long-term studies showed complete restitution following grade 1 and 2 trauma, whereas after a grade 3 lesion a small segmental and capsular fibrosis without hyperplasia of the juxtaglomerular apparatus was observed. Based on the characteristic ultrasound pattern found in the first study, the threshold for induction of grade 1 lesion was investigated. With both lithotripters a wide range for induction of a grade 1 lesion (Modulith 234-411, Lithostar Plus 220-740) and also a significant overlapping with grade 0 and 2 lesions was seen at low energy settings (levels 2-4). In contrast, the range of shocks (Modulith 96-150, Lithostar Plus 90-142) and overlapping was minimal when high energy was used (levels 7-9). Finally, the disintegration-trauma coefficient combining the results obtained in a standard stone model with those of the canine kidney model was introduced.

Animals↗
PubMed1993

Transperitoneal laparoscopic nephrectomy: training, technique, and results.

Transperitoneal laparoscopic nephrectomy was integrated into our daily routine within a 6-month period by means of a step-by-step training program progressing from a pelvic trainer to animal studies (N = 15) to laptent-assisted surgery. The pneumoperitoneum is created with the patient in the flank position, enabling insertion of three trocars: 10-mm periumbilical (Port I), 5/12-mm subcostal (Port II), and 12/5-mm above the iliac spine (Port III). After medial mobilization of the colon, two additional 5-mm trocars (Ports IV and V) are inserted into the lateral abdominal wall parallel to Ports II and III. Once clipping and dissection of the ovarian (spermatic) vein has been carried out, the ureter is identified and dissected. Retraction of the proximal ureter exposes the renal hilum, allowing dissection of the renal vessels. The renal vein is dissected using an endoscopic stapling device, while accessory veins and the renal artery are clipped. Organ retrieval is achieved with a specially designed tissue pouch (Lapsac) and digital fragmentation of the kidney within the organ bag. Using this technique, we have treated 24 patients with benign (N = 20) and malignant (N = 4, including adrenalectomy) renal disease. The mean operative time was 239 (115-300) minutes. In four cases, open surgery was required because of bleeding (N = 2), severe perinephric inflammation (N = 1), or bowel injury (N = 1). For relief of wound pain, an average of 1.15 vials of analgesic (morphine derivatives)/patient were administered for 2.4 days. The postoperative hospital stay averaged 6.2 (4-10) days.

Animals↗
PubMed1993

Intra- and perivesical tumor growth in preoperative staging of bladder cancer: the role of transrectal ultrasonography and high resolution magnetic resonance imaging.

Bladder tumors were staged preoperatively before and/or after M-VEC poly-chemotherapy using transrectal ultrasonography and magnetic resonance imaging in 46 patients. The resultant findings were each compared with histomorphologic results. The sensitivity of both methods compared with pathohistology was 88%. Using this technique, the degree of tumor invasion of the bladder wall could be evaluated and the appropriate therapy selected. Further applications included the monitoring of transurethral resection determine its adequacy as a treatment modality.

Adenocarcinoma↗
PubMed1993

The effect of single shock waves on the vascular system of artificially perfused rabbit kidneys.

Extracorporeally-perfused rabbit kidneys were exposed to five shock waves at 14 kV on the XL1 Dornier experimental lithotripter (Dornier Medical Systems, Inc., Germering, Germany). While the perfusion flow rate was kept constant, the arterial perfusion pressure was recorded to assess changes in vascular resistance. Immediately after shock wave application, perfusion pressure decreased by 20%-30%, followed by a short, relative pressure rise that did not reach pretreatment values. Fifteen-twenty minutes later, arterial perfusion pressure reattained pretreatment values. Subsequent to treatment, urine flow decreased by greater than 50%. The observed pressure rise was also induced in nontreated kidneys by perfusion with the effluent of treated kidneys indicating that this is based on a humoral mechanism. On the other hand, shock wave application to formalin fixed kidneys only caused a marked decrease in arterial perfusion pressure, suggesting that this effect is due to a pure mechanical interaction of the shock wave also found with denaturated kidneys. The observed decrease of urine flow is probably caused by a decreased filtration rate. Since this was not the case in nontreated kidneys being perfused with the effluent of treated kidneys, the reduction of urine flow after extracorporeal shock wave lithotripsy does not appear to be mediated by a humoral factor, but is more likely a result of the mechanically-induced vasodilation with consecutive decline of the glomerular filtration rate.

Animals↗
PubMed1993

[Antegrade-retrograde urethrotomy in therapy of high degree urethral stricture].

In the case of urethral stricture which is non-passable by conventional "cold knife" urethrotomy, open urethroplasty can be avoided by combined antegrade-retrograde urethrotomy (ARUT). A rigid cystoscope is guided, through a dilated, suprapubic cystostomy channel, to the stricture in the membranous or bulbular urethra. A urethrotome is inserted in the retrograde direction and the "cut to the light" procedure is adopted. Using the ARUT method, successful realignment was achieved in 9 patients; 4 strictures were trauma- or urethritis-induced and 5 were the result of transurethral management. Recurrent stricture in 4 out of 7 cases (57%) required further urethrotomy. There was no recurrence in 4 out of 7 patients for at least 5 months subsequent to the last treatment. All patients were spared open surgery. The antegrade-retrograde technique exists since 1978. Up to date, 63 cases have been mentioned in the literature. The primary therapy success rate is 25%. Successful retreatment following recurrence was observed in 65%. We recommend ARUT as first-choice treatment for severe strictures of the bulbular and membranous urethra.

Adult↗
PubMed1993

[Parameters influencing the incidence of recurrent urinary calculus after ESWL].

With extracorporeal shock wave lithotripsy, stone fragmentation and the potential creation of residual stones has become an integral part of the treatment strategy. Therefore, true recurrence, regrowth and pseudo-recurrence determine the rate of new stone formation. In nonselected series the overall recurrence rate after ESWL varies between 6% after 1 year and 20% after 4 years. The comparison between recurrence rate after ESWL and the natural recurrence rate reveals that the results of ESWL are better than expected. Lithotripsy has no specific effect on true stone recurrence, and even the pseudo-recurrence is of minor clinical significance. Nevertheless, metaphylaxis keeps its place in treatment of recurrent urolithiasis.

Follow-Up Studies↗