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Biomedical subjects

P Alken

Publications and source records attributed to P Alken.

At least 19 recordsLinked to original sources
PubMed1996

Rotoresect: new technique for resection of the prostate: experimental phase.

We developed a new resection device-the Rotoresect -with the aim of reducing morbidity during transurethral resection of the prostate (TURP). During rotoresection, a rotating ablator electrode enables simultaneous tissue coagulation by high-frequency current and mechanical tissue ablation. The tissue ablation rate and the extent of bleeding were quantified ex vivo using a blood-perfused porcine kidney (N = 30) and then compared with loop resection and electrovaporization (grooved roller/Rollerball). Additionally, transurethral rotoresection of the prostate and open partial resection of the liver were carried out in five dogs. With the blood-perfused porcine kidney, we demonstrated that the tissue ablation rate increases with increasing of the coagulation current and rotation speed of the ablator electrode. The Rotoresect achieved a tissue ablation rate comparable to that of the resection loop (5.5-6.0 g/min), which was more than twice the rate achieved by electrovaporization (1.7-2.0 g/min). The extent of bleeding during standard loop resection was many times higher (16.5-18.0 g/min) than that induced by rotoresection and electrovaporization (< 2.3 g/min). In our in vivo canine trials, we performed transurethral prostate resection and open segmental liver resection with minimal bleeding. The Rotoresect is a promising instrument for ablation of parenchymal organs during transurethral, laparoscopic, and open surgical procedures.

Animals↗
PubMed1996

New methods of searching for medical literature: comparison of two systems, implementation and user reactions in a urologic department.

Knowledge Finder is the first Medline retrieval system based on CD-ROM technology that allows natural-language queries and accounts for deviations in spelling and terminology. Retrieved citations are ranked in accordance with their possible relevance (fuzzy logic algorithms), thus resulting in speedy orientation on a topic of interest. EasyOrder is an additional software module that enables the user to place an automatic electronic order at the library of choice, via modem, to receive a copy of a full-text article by mail or facsimile. We performed a study comparing search results and times when using a Boolean versus a fuzzy system. This article describes the underlying new concepts, implementation in a urologic department and user reactions to the new possibilities.

CD-ROM↗
PubMed1996

Recording the corpus cavernosum electromyogram: principles and problems.

PURPOSE: To apply digital signal acquisition and analyzing techniques to the collection and interpretation of electromyographic data of the cavernous body. MATERIALS AND METHODS: Electromyographic recordings were performed in the cavernous bodies of anesthetized, spontaneously breathing dogs under resting conditions and after intracavernous pharmacostimulation with norepinephrine, angiotensin II, phentolamine/papaverine, diethylether and T61. RESULTS: Resting corpus cavernosum activity was ill-coordinated and provided little information. Signal energy was confined largely to the range below 20 Hz. Pharmacostimulation with norepinephrine or angiotensin increased frequency and amplitude of the potential transients and decreased the random components. Administration of a combination of phentolamine and papaverine made the signals very regular and increased periodicity. Blockade of electrical membrane events with diethylether removed all signal components except for electrical and biological noise. CONCLUSIONS: Our findings indicate that electromyograms from the corpus cavernosum can be recorded even under adverse conditions. Signal properties, however, are such that the application of computer-aided data processing and analysis to the evaluation of these myograms is imperative.

Amides↗
PubMed1996

Laparoscopic retroperitoneal lymph node dissection for nonseminomatous germ cell tumors: indications and limitations.

PURPOSE: We describe our experience with laparoscopic retroperitoneal lymph node dissection in 26 patients with nonseminomatous germ cell tumors: 17 had stage I disease with no clinical (computerized tomography, ultrasound or tumor markers) evidence of metastases and 9 (2 with stage IIb and 7 with stage IIc disease) had residual tumor after chemotherapy but with negative tumor markers. Laparoscopic dissection was performed to assess more fully pathological status of the relevant retroperitoneal lymph nodes in both groups. MATERIALS AND METHODS: The patient was positioned and trocars were introduced at sites similar to that used for transperitoneal laparoscopic nephrectomy (flank position with 3, 10 mm. and 2, 5 mm. ports). After the white line of Toldt was incised and the colon was reflected anteromedially, the retroperitoneal space was exposed. The landmarks of lymph node dissection were then isolated, including the ureter, aorta, inferior vena cava and both renal veins. Lymph node dissection was performed identical to that for open surgery, with a modified template including the paracaval, interaortocaval, upper preaortic and right common iliac nodes for right tumors, and para-aortic and upper preaortic nodes for left tumors. Lymph node chains were retrieved with a small organ bag. RESULTS: The procedure was completed successfully in 16 of 17 patients with stage I disease (mean duration 268 minutes for the left and 312 minutes for the right sides). No intraoperative complications were encountered. One patient had delayed ureteral stenosis requiring operative repair, 1 had a pulmonary embolism with an uneventful outcome and 1 who underwent laparoscopic retroperitoneal lymph node dissection on the right side later had retrograde ejaculation. Embryonal carcinoma was found in 1 of the 17 patients. Average postoperative hospital stay was 4.5 days for patients without complications or conversion to an open procedure. After a median followup of 27 months no patient had regional relapse but 2 had pulmonary metastases that were treated successfully with 3 cycles of platinum based chemotherapy. Laparoscopic dissection was significantly more difficult in patients with stage II tumors after chemotherapy. Only in 2 patients with stage IIb disease was laparoscopic lymphadenectomy successful. In 5 of the 7 patients with stage IIc cancer portions of the dissection had to be done after conversion to an open (conventional) operation via a small incision (suprainguinal or pararectal). In 1 patient the laparoscopic approach was completely abandoned and converted to an open operation via a standard midline incision. In all 9 cases histopathological examination revealed complete necrosis. No patient has evidence of disease. CONCLUSIONS: Our preliminary experience suggests that a modified laparoscopic retroperitoneal lymph node dissection is feasible for stage I tumors. However, it cannot be recommended after previous chemotherapy (stages IIb and IIc disease).

Follow-Up Studies↗
PubMed1996

[Retroperitoneoscopy. Technique and experiences with the first 100 patients].

Retroperitoneoscopic procedures were already being performed in the late 1970s. The clinical breakthrough of retroperitoneoscopy, however, was initiated in 1992 by the balloon-dissecting technique of Gaur, together with the experience gained with transperitoneal laparoscopic procedures in the upper retroperitoneum. We have modified the balloon-dissecting technique into a hydraulic video-optically controlled balloon dissection of the retroperitoneal space, and this procedure was recently further simplified. From December 1992 to December 1995 we performed 100 retroperitoneoscopic procedures in 98 patients (aged 4-82 years). Twenty-two patients had undergone previous abdominal surgery, 16 patients had been operated on for kidney and ureter problems. We performed 28 simple procedures (6 renal biopsies, 17 renal cyst resections, 4 ureterocutaneostomies, 1 foreign body retrieval), 65 difficult operations (47 nephrectomies, 5 nephroureterectomies, 5 nephropexies, 4 ureterolithotomies, 2x ureterolysis). There were also 9 complicated cases (5 heminephrectomies, 2 tumor nephrectomies, 2 dismembered pyeloplasties). Operating time, complications and conversion rate to open surgery mainly depended on the difficulty of the procedure and the personal learning curve, resulting in 50-90 min, 0% and 3.8%, respectively, for an easy retroperitoneoscopy, 90-210 min, 12% and 9.2% respectively for a difficult operation, and 180-390 min, 22% and 11%, respectively, for a very difficult procedure. Excluding the 17 patients with complications or conversion (unclear anatomy, extremely difficult dissection), the mean postoperative need for analgesics was 0.7 vials, and the mean hospital stay was 4.7 days. We have now passed most of our learning curve, and retroperitoneoscopy has become a standardized procedure that is a part of the training program for the experienced urologist.

Biopsy↗
PubMed1996

[Transperitoneal and retroperitoneal laparoscopic nephrectomy in comparison with conventional nephrectomy].

We report on our clinical experience with laparoscopic nephrectomy in 35 patients. We have performed a total of 18 transperitoneal laparoscopic nephrectomies (TLN) for benign renal disease. After the introduction of a hydraulic dissecting device, we have since performed 17 retroperitoneal laparoscopic nephrectomies (RLN). These data were compared with those in 19 consecutive open nephrectomies (N). All groups were comparable in terms of indication. The mean operative time for benign disease was 206.5 min for TLN, 211.2 min for RLN and 117 min for N. Analgesic medication requirement per patient was 2 days for TLN, 1 day for RLN and 4 days for N, while the postoperative hospital stay averaged 7 days for TLN, 6 days for RLN and 10 days for N. Our results demonstrate the advantage of a laparoscopic approach over open surgery and also reveal the distinct benefit of a retroperitoneal approach. However, due to the small number of indications this procedure should be restricted to a few urologic centers.

Humans↗
PubMed1996

Retroperitoneal laparoscopic lymph node dissection for staging non-seminomatous germ cell tumors before and after chemotherapy.

We describe our experience with laparoscopic retroperitoneal lymph node dissection in 19 patients with non-seminomatous germ cell tumors. Twelve patients had stage I disease with no clinical evidence (CT-scan, ultrasound, tumor markers) of metastases; 7 patients (stage IIb=2, stage IIc=5) had residual tumor after chemotherapy but with negative tumor markers. A laparoscopic dissection was used to asses more fully the pathologic status of the relevant retroperitoneal lymph nodes of both groups. The patient was positioned and trocars introduced at sites similar to that used for transperitoneal laparoscopic nephrectomy (flank position, five ports - 3 x 10 mm; 2 x 5 mm). After reflecting the colon anteromedially, the landmarks of the lymph node dissection were isolated-namely the ureter, aorta, inferior vena cava, and both renal veins. The lymph node dissection included the paracaval, interaorto-caval, upper preaortic, and right common iliac zonal nodes for right-sided tumors, and paraaortic, upper preaortic zones for left-sided tumors. Retrieval of the lymph nodal chains was accomplished using a small organ bag. The mean duration of the procedure was 298 (range 150-405) minutes. In only one patient was a lymph node positive for tumor (stage I). Otherwise nodes showed extensive necrosis (after chemotherapy). No intraoperative complications were encountered but three patients developed a delayed complication (ureteral stenosis, pulmonary embolism, and retrograde ejaculation, respectively). Whereas we completed the dissection in each patient with stage I tumors, the laparoscopic procedure was more difficult in patients with stage II tumors after chemotherapy. In two patients with stage IIb disease laparoscopic lymphadenectomy was successful. In four other patients parts of the dissection had to be done after conversion to an open (conventional) operation using a small incision (suprainguinal or pararectal); in one patient the laparoscopic approach was abandoned and converted to an open operation. In the post-chemotherapy group the outcome depended primarily on the tumor bulk prior to drug treatment. In two patients in whom all residual necrotic tissue was removed laparoscopically they had "minor" disease (stage IIb); the others had stage IIc tumors. Our preliminary experience suggests that a modified laparoscopic lymph node dissection is feasible for stage I tumors and in selected patients with marker negative residual tumor after chemotherapy (stage IIb).

Feasibility Studies↗
PubMed1995

Establishment and characterization of a multidrug-resistant human bladder carcinoma cell line RT112/D21.

A doxorubicin-resistant human bladder carcinoma cell line RT112/D21 was established by continuous exposure of the parental line RT112 to increasing concentrations of doxorubicin over a period of 9 months. RT112/D21 cells expressed significantly more P-170 glycoprotein than the parental line, and rhodamine 123 efflux, as a functional parameter of P-170 glycoprotein activity, was increased. RT112/D21 cells were 96 times more resistant to doxorubicin than RT112 cells, and cross-resistance to epirubicin and vinblastine was present. Sensitivity to methotrexate and mitomycin C remained unchanged. R-verapamil reversed resistance to doxorubicin, epirubicin and vinblastine in RT112/D21 cells but did not affect sensitivity to methotrexate and mitomycin C. In RT112 cells, R-verapamil had no effect on drug sensitivity. Thus, it may be assumed that primary or induced MDR1 gene-encoded P-170 glycoprotein expression is a relevant mechanism of chemoresistance in transitional cell carcinoma, and that chemotherapeutic strategies in combination with chemosensitizers improve response rates.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Ureteral laparoscopic surgery.

During the past years, laparoscopy has grown in popularity and become an alternative technique for the treatment of certain pathologies in urological practice. Retroperitoneal laparoscopic procedures for ureteral surgery were first attempted by Wickham in 1979: in this case a patient with a ureteral calculus underwent a successful ureterolithotomy; More recently, the introduction of the Gaur balloon has permitted quick dilatation and easier access to the retroperitoneum. However, in comparison, the transperitoneal method offers more space and better vision for identification of anatomical landmarks. In our clinic, we have performed laparoscopic ureteral surgery using the transperitoneal as well as the retroperitoneal approach. For situations requiring reconstructive surgery, we preferred the transperitoneal approach in 3 cases of ureterolysis; 2 diagnostical and 1 therapeutical. On the other hand, the retroperitoneal approach was employed for carrying out 2 pyeloplasty, 1 ureterocutaneostomy and 1 ureterolithotomy. Furthermore, we performed in similar fashion 3 nephroureterectomy and 1 heminephrectomy combined with partial ureterectomy. In 3 cases, transperitoneal nephroureterectomy with transurethral orifice circumcision was carried out. In all patients, laparoscopy revealed low morbidity with low grade postoperative pain and shorter hospital stay. Our experience shows that the progressive use of retroperitoneoscopic surgery can maintain minimal invasiveness and permit good access to various procedures without complications connected to use of the Veress needle or the presence of abdominal adhesions. In addition to our own laparoscopic experience, we have reviewed the literature and report on the most frequent ureteral surgery performed laparoscopically.

Humans↗
PubMed1995

The clinical introduction of a third generation lithotriptor: Modulith SL 20.

The Modulith SL 20* was designed as a third generation lithotriptor with outstanding disintegrative efficacy in vitro, and equipped with a combined fluoroscopic and ultrasound localization system integrated in a multifunctional table. Its introduction to clinical extracorporeal shock wave lithotripsy took place in 3 phases. In phase 1 (49 patients) only in line ultrasound localization was possible. The many caliceal stones were adequately disintegrated with restricted generator voltage. In phase 2 (81 patients) fluoroscopic localization with the virtual focus of an adapted x-ray C-arm unit enabled in situ lithotripsy of ureteral stones in 33% of all patients. Phase 3 (549 patients) was characterized by additionally increasing the generator voltage to 20 kv. This development of the lithotriptor by improving the localization system and shock wave energy resulted in the possibility for successful disintegration of stones in the entire upper urinary tract (including the complete ureter), decreased treatment time (52 to 39 minutes) and an improved efficiency quotient (0.45 to 0.67). During phase 3 auxiliary measures were performed before lithotripsy in 24% of the cases. After 1.8% of the treatments minor or moderate perirenal fluid collection or bleeding was detected by routine followup sonography. A 91% stone-free rate was achieved with only 9.3% curative auxiliary measures after extracorporeal shock wave lithotripsy, including a 23% retreatment rate. Thus, the Modulith device had a high efficacy quotient compared with other lithotriptors.

Adult↗
PubMed1994

Basic experimental studies on corpus cavernosum electromyography and smooth-muscle electromyography of the urinary bladder.

In contrast to the extensive work on in vitro experiments for elucidation of the electrical properties of smooth musculature, the acquisition of knowledge on electrical signal behaviour from smooth-muscle cells in an in vivo situation remains very limited and rare. Smooth-muscle electromyographic recording from the smooth musculature of the genitourinary tract, in particular from the penile cavernous bodies and the urinary bladder, has recently become one of the most interesting issues in both impotence research as well as neurophysiological assessment of the urinary bladder. However, the inadequate available data on corpus cavernosum and EMG recordings remains controversial due to the significant discrepancy between basic physiology of the smooth musculature, technical prerequisites and the expected clinical impact from the smooth-muscle EMG of genitourinary organs. This article is an attempt to describe the fundamentals of smooth-muscle EMG signal behaviour and the technical prerequisites for data acquisition and analysis of electrical activity from smooth-muscle cells of the cavernous bodies and urinary bladder. A description is given of the technical aspects, including methodology and interpretation of the recorded data, and also of the possible interference by artefacts (endogeneous and exogeneous) that might limit the clinical relevance of this encouraging method. The advantages, pitfalls and limitations of online analogous data registration and the possibility of computer-assisted smooth-muscle electrical activity recording and analysis are demonstrated by basic in vivo studies on cavernous bodies and also the detrusor muscle.

Animals↗
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

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

Retroperitoneal laparoscopic nephrectomy and other procedures in the upper retroperitoneum using a balloon dissection technique.

This article describes a hydraulic balloon dissection technique. The retroperitoneum is developed via a small lumbodorsal incision between the edges of the musculus latissimus dorsi and musculus obliquus externus and then after visualization of its correct position the balloon catheter is filled with 500-1,200 ml of warm normal saline (according to patient size). The device consists of the finger of a surgeon's glove ligated around the end of a rigid bladder catheter. The balloon insufflation is maintained for 5 min to guarantee adequate hemostasis. Recently, we have replaced the balloon catheter by a balloon trocar sheath allowing direct endoscopic control of the hydraulic dissection. After retrieval of the balloon the CO2 insufflator is connected to the first trocar. All secondary trocars are placed under endoscopic control. The hydraulic dissection techniques also enable optimal creation of an effective pneumoperitoneum in children. Until now, we have used this technique for twelve procedures in the upper retroperitoneum including five nephrectomies, two nephroureterectomies, one tumor nephrectomy, one nephropexy, one renal cyst marsupialization and two renal biopsies. Up to now we have encountered no major complications. Three of the nephrectomized patients had undergone multiple previous abdominal surgical interventions. The retroperitoneal approach allows the surgeon to apply similar dissecting techniques as used in respective open procedures. It has become the routine approach for laparoscopic procedures in benign renal disease. This procedure can be performed even in cases with previous abdominal surgery.

Adult↗