nitinol and Ureteral-Obstruction

To evaluate the efficacy of Nitinol (Memotherm) self-expandible metal stents in the treatment of malignant and non-malignant ureteral obstruction in patients who are not eligible for surgery.. A total of 14 ureteral strictures (5 malignant, 9 non-malignant) in 13 patients were treated by the implantation of a Nitinol endoprosthesis. Eight were implanted by the antegrade and 6 by the retrograde route. A mean of 1.3 stents were implanted per patient.. 85% of the stents were patent at a mean follow-up of 10.2 months (range 2-28). Four prostheses developed transient obstruction that was resolved by insertion of a double-J catheter for periods that ranged from 2 to 6 months. One stent required a permanent double-J catheter and another stent showed functional obstruction, although it was morphologically patent.. The Nitinol self-expandible metal stent is effective in the treatment of malignant and non-malignant ureteral obstructions in patients who are not eligible for surgery due to the tumor stage or high surgical risk.

Topics: Adult; Aged; Aged, 80 and over; Alloys; Female; Humans; Male; Middle Aged; Stents; Ureteral Obstruction

We have developed the Peralta Stone Extraction System to increase the safety of ureteral stone extraction. The device combines a nitinol stone basket and low-pressure balloon into a single device. After visualization, the stone is captured in the tipless nitinol basket and enveloped by a low-pressure balloon. We tested the performance of device prototypes in a porcine model using stone mimics with diameters ranging from 4.2 to 6.2 mm. Stones extracted with the device required less force when compared with stones in a standard ureteral stone basket. The force reduction was most pronounced for stones greater than 4.2 mm in diameter, and when traversing a ureteral stenosis model. In conclusion, a combination stone basket and balloon device may provide a new and safer way to extract ureteral stones.

Topics: Alloys; Animals; Dilatation; Humans; Hysteroscopes; Male; Swine; Ureteral Calculi; Ureteral Obstruction; Ureteroscopy

The aim of this study was to investigate the long-term outcome of a thermoexpandable nickel-titanium nitinol ureteral stent (Memokath 051™) and to identify individual risk factors for failure.. This retrospective single-centre study included 125 patients who underwent implantation of the self-expandable Memokath 051 stent. Complications, indwelling time and reason for explantation were recorded. Analyses were stratified by gender, age, body mass index, American Society of Anesthesiologists score, estimated glomerular filtration rate (eGFR), side, localization and cause of the stricture.. In total, 91 out of 125 patients (73%) were available for analysis. Median indwelling time was 355 days (range 7-2125 days). Most stents were removed because of dislocation (42%) or occlusion (40%). Stent removal was rarely performed because of infection (3%). Patients with sufficient renal function (eGFR ≥60 ml/min/1.73 m²) showed increased indwelling times compared with those with nephropathy (386 vs 317 days; p < 0.01). Patients with active malignant disease showed reduced patency time compared with strictures of benign origin (455 vs 190 days; p < 0.01).. This thermoexpandable nitinol stent offers safe mid-term treatment of ureteric strictures, especially in patients without active malignancy and with good renal function.

Topics: Aged; Alloys; Device Removal; Female; Glomerular Filtration Rate; Humans; Kidney Diseases; Male; Middle Aged; Prosthesis Failure; Retrospective Studies; Risk Factors; Self Expandable Metallic Stents; Time Factors; Ureteral Obstruction

To test the effectiveness of nitinol stents in restoring patency of pyeloureteral segment (PUS).. Endoureteral nitinol stents were used in 54 patients. The indications for stenting were recurrent strictures of upper urinary tract and ureteral tumor obstruction in 34 and 20 patients, respectively. In 9 (16.6%) of them, including 4 women and 5 men aged 28-65 years, stenting was performed for extensive recurrent PUS strictures. In 8 patients extensive strictures resulted from various surgical interventions on the PUS. In 2 patients, PUS narrowing was caused by open pyelolithotomy, in 6 patients by pyeloplasty, both open (4) and laparoscopic (2). A female patient with solitary right kidney and Bourneville - Pringle disease of the PUS received two metal prostheses.. In all cases, nitinol stents were adequately installed in PUS. Hematuria was observed in 1 patient. During the follow-up period of 8 to 60 months, the results of stenting were considered good in 6 (66.7%) and satisfactory in 2 (22.2%) patients. At month 10, 1 (11.1%) patient developed the stent obstruction by proliferative tissue and underwent ureteroscopy with recanalization of the nitinol stent. The patient with Bourneville - Pringle disease was found to have a stone formed in the renal pelvic end of the endoprosthesis; she underwent percutaneous nephrolithotripsy. In another patient a lower calyceal stone migrated and wedged into the proximal end of the stent. The stone was extracted using percutaneous nephroscopy.. Pyeloureteral stenting is an effective method to restore patency of the PUS in patients with extensive recurrent strictures. For adequate functioning of the stents, they need to be of optimal length and correctly installed.

Topics: Adult; Aged; Alloys; Female; Humans; Kidney Pelvis; Male; Middle Aged; Postoperative Complications; Stents; Treatment Outcome; Ureteral Obstruction; Urologic Surgical Procedures

Chronic ureteral stricture and ureteral fistula are treated with urinary diversion using percutaneous nephrostomy or double pigtail stent. Both of these techniques require replacement of the tube every few months in order to prevent encrustations and obstruction.. To report the long-term efficacy of the new Allium Ureteral Stent (URS) in the treatment of ureteral stricture and fistula.. The Allium URS is a newly-developed ureteral stent made of nickel-titanium (Nitinol), which is inserted in a small diameter and spontaneously expands into and preserves a large-caliber. The stent is coated with a biochemical co-polymer which prevents tissue ingrowth and incrustations. The stent is inserted antegradely or retrogradely with intraoperative x-ray guidance after dilation of the stricture. The Allium URS stent was inserted into 107 ureters of 92 patients in 5 different centers worldwide; 69 patients carried a percutaneous nephrostomy before the procedure and 38 patients had a ureteral stent. The etiologies underlying the strictures were: gynecological cancer (with or without irradiation), bladder cancer, iatrogenic stricture, ureteroileal stenosis, stricture following uretero-pelvic junction obstruction repair and iatrogenic ureteral fistula.. During a mean follow-up of 27 months, only one stent was obstructed after eleven-indwelling months; 21 patients died of their primary disease carrying the stent. Stent migration was seen in 11 patients within 8 months after its insertion, and these stents were removed. In 4 patients with early stent migration, the stents were replaced. In 18 patients the stents were removed as planned after one year of indwelling time, and these patients were asymptomatic in a follow-up period of up to 59 months.. The results of our study show that the use of Allium URS for the treatment of ureteral strictures is feasible, safe and effective. The relative ease of its insertion could encourage its use in a wide range of other indications.. Due to its unique structure, the Allium URS is superior to the regular pigtail stents in the treatment of ureteral strictures. Stent migration was seen in only 10.7% of the patients, mainly in patients with stricture of the mid-ureter.. The use of the Allium URS stent in the treatment of proximal and distaL ureteral strictures is safe and effective.

Topics: Alloys; Fistula; Follow-Up Studies; Humans; Prosthesis Design; Stents; Time Factors; Ureter; Ureteral Obstruction

Ureteral obstruction in renal transplant allografts secondary to strictures can pose a challenging problem. Its incidence is reported between 0.5% and 4.7%. Usually, open surgical repair is performed. We present a series of patients in whom a metal Memokath™ 051 stent has been used as a minimally invasive treatment alternative.. We analyzed our data on the use of thermo-expandable metallic Memokath 051 stents for ureteral strictures in renal transplant patients.. Between 2003 and 2010, eight male kidney recipients with a mean age of 49 years and obstructed ureters after kidney transplantation were treated with ureteral Memokath insertion. In six patients, the obstruction was at the level of the anastomosis, and in two, at the pelviureteral junction. After a mean follow-up of 4 years, half of the stents are in situ providing a good graft function. The average indwelling time is 4 years. Spontaneous resolution of the stricture without the need for further stent insertion was seen in three patients after a mean indwelling time of 7.3 months. There was one treatment failure in a patient with an obstructed, dilated, and convoluted ureter that was unable to withhold the stent in situ. No perioperative complications were recorded in this series. The overall success rate was 87%.. Ureteral stent placement with the Memokath 051 is a safe minimally invasive treatment alternative for ureteral strictures in renal transplant recipients.

Topics: Adult; Aged; Alloys; Female; Follow-Up Studies; Humans; Kidney Transplantation; Male; Middle Aged; Minimally Invasive Surgical Procedures; Prosthesis Design; Retrospective Studies; Stents; Treatment Outcome; Ureter; Ureteral Obstruction

Stents are used abundantly to maintain ureteral patency. The majority are plastic tubes that adjust easily to upper urinary-tract motion. Recently, a coiled-wire lumenless stent was introduced (ZebraStent, Neo Medical, Munich, Germany) to facilitate expulsion of stone fragments after lithotripsy. Its metal core is composed of Nitinol, with the soft J ends being of titanium. The thin shape considerably increases the extraluminal space. The ZebraStent stretches the ureter and also provides a surface for the fragments to glide along. In our 18-month experience with the ZebraStent, two of them fractured along the shaft. We sought to learn whether this complication resulted from a defect in stent design or from material fatigue secondary to constant movement.. Our model is powered by an electric motor that produces a constant displacement similar to stent movements in vivo. The whole ZebraStent is embedded in a 37 degrees C waterbath to simulate physiological conditions within the ureter. We used an average displacement of 16 mm. The average frequency of ventilatory-cycle simulation was 20 times that in vivo, allowing us to collect data in a shorter time.. All 10 stents broke within the proximal Nitinol shaft at the equivalent of 4 to 6 months (125-179 days).. Our preliminary results show that all stents break after the equivalent of 4 or more months. The fact that this occurs in the homogenous proximal Nitinol shaft rather than at the welding point between the shaft and the titanium curl implies that breakage is secondary to material fatigue and not design error. Extensive testing is under way to confirm material fatigue as the cause of breakage. We hope to determine a safe dwelling time for these stents, which at the moment should not exceed 3 months.

Topics: Alloys; Feasibility Studies; Humans; Materials Testing; Models, Anatomic; Prosthesis Design; Prosthesis Implantation; Stents; Stress, Mechanical; Titanium; Ureteral Calculi; Ureteral Obstruction

We developed a technique for laparoscopic ureterocalicostomy with the use of intracorporeal suturing and subsequently simplified the technique by application of experimental Nitinol clips.. We performed laparoscopic ureterocalicostomy on 16 domestic swine divided into four groups of four animals each. The kidney was exposed laparoscopically, and the renal artery was atraumatically clamped. The lower pole of the kidney was amputated to expose a lower-pole calix, and hemostasis of the cut renal surface was obtained with a wet monopolar electrosurgical device (Floating Ball device [FB]; TissueLink, Dover, NH). Anastomosis of the ureter to the lower-pole calix was performed over a guidewire using 3-0 Vicryl suture in group 1 and Nitinol clips in group 3. A double-J ureteral stent was then deployed retrograde under fluoroscopic guidance. In addition, we evaluated the use of fibrin glue as a sealant over the sutured or clipped anastomotic site (groups 2 and 4, respectively). Ureteral stents were removed after 3 weeks, and the animals were evaluated and sacrificed after an additional 3 weeks.. Laparoscopic ureterocalicostomy was completed in all 16 animals. In each case, excellent renal parenchymal hemostasis was obtained with the FB device, with a mean hemostasis time of 4.1 minutes. The mean anastomotic time with standard suture reconstruction was 37.1 +/- 5.4 minutes, while the anastomotic time with the Nitinol clips was 29.0 +/- 8.0 minutes (P = 0.0339). Retrograde pyelograms in groups 1 and 3 (no fibrin glue) showed a patent anastomosis with no hydronephrosis in three of the four animals in each group. One animal in group 1 and one animal in group 3 developed large urinomas secondary to anastomotic failure. The animals that received fibrin glue over the anastomotic site (groups 2 and 4) all showed narrowed anastomoses with severe hydronephrosis.. With available instrumentation, laparoscopic ureterocalicostomy is technically feasible. Nitinol clip technology significantly reduces collecting-system reconstruction time. Application of fibrin glue as a urinary tract sealant resulted in an unexpected adverse outcome.

Topics: Alloys; Anastomosis, Surgical; Animals; Constriction, Pathologic; Electrosurgery; Fibrin Tissue Adhesive; Hemostatics; Hydronephrosis; Kidney Calices; Laparoscopy; Models, Animal; Radiography; Stents; Sutures; Swine; Ureter; Ureteral Obstruction; Ureterostomy

Topics: Alloys; Angiography, Digital Subtraction; Angioplasty, Balloon; Blood Vessel Prosthesis; Blood Vessel Prosthesis Implantation; Constriction, Pathologic; Female; Humans; Iliac Artery; Inflammation; Middle Aged; Polyethylene Terephthalates; Recurrence; Stents; Syndrome; Ureter; Ureteral Obstruction