Coated v noncoated ureteral metal stents: an experimental model.

PURPOSE: The purpose of the present study was to compare the standard metal stents with internally and externally coated metal stents in the pig model. MATERIALS AND METHODS: In nine female pigs weighing between 25 and 30 kg, the metal stents were randomly placed in either the right or left ureter, for a total of 18 stented ureters. Six ureters were stented with a Wallstent (Schneider, Zurich, Switzerland), six with a Passager stent (Boston Scientific, Natick, MA, USA), and six with a Corvita endoluminal graft (CEG) (Boston Scientific, Natick, MA, USA). Patency was examined by nephrostotomography 24 hours and 21 days after the initial procedure. RESULTS: Free flow of urine through the stents into the bladder was revealed in all ureters with the exemption of four cases where a Passager stent migrated into the bladder, jeopardizing ureteral patency. The Wallstent generated mild inflammation with metaplasia of the urothelium; the CEG a more pronounced inflammatory response in the adjacent ureter; and the Passager stent severe inflammatory reaction with necrosis of the urothelium. The sections of the Wallstents revealed the presence of a mild polypoid reaction adherent to the internal surface of the devices. The coated stents showed no tissue ingrowth through the lining material into the ureteral lumen, and thus, the urothelium was compressed beneath the prostheses. CONCLUSIONS: Our experimental results suggest that the standard Wallstent generates less inflammation of the surrounding tissues than coated stents. The coated stents have the advantage of minimal tissue ingrowth but have a tendency to migrate toward the bladder.     

Optical coherence tomography provides images similar to histology and allows the performance of extensive measurements of drug-eluting metal stents in animal ureters

Optical coherence tomography (OCT) images and histology images of metal stents (MSs) inserted in animal ureters were compared, and the reliability of an OCT-based automated method for the performance of quantitative evaluation of ureteral MSs was evaluated. A zotarolimus-eluting metal stent (ZES) and a bare metal stent (BMS) were inserted in each ureter of ten pigs and six rabbits. OCT was performed in unobstructed stented ureters. Histopathologic examination of the stented ureters embedded in glycol-methacrylate took place. Quadrants of OCT images were compared to their respective histologic images by employing two independent observers who delineated different layers in the quadrants of OCT images and correlated them to the respective histologic quadrants. Manual (integrated OCT device software) and automated measurements of the OCT images using an automated strut detection method were compared. The observers highly agreed on the delineation of urothelium from the lamina propria and the lamina propria from the muscle layer of the ureteral wall. The algorithm measurements were similar to the manual measurements, and the algorithm proved to be reliable in the evaluation of ureteral MSs. Significantly higher endothelial hyperplasia of the BMSs in comparison to the ZESs was also quantitatively demonstrated by the strut detection method. OCT proved to be a reliable method for the evaluation of ureteral MSs. OCT provided images of the stented ureteral lumen similar to light microscopy quality. Measurements of the stented ureter are reliably performed by the automated strut detection method.     

Therapy of extrinsic ureteral obstruction with 2 parallel ureteral Double-J stents

We present our experiences with the approach of placing 2 parallel ureteral Double-J stents simultaneously in extrinsically obstructed ureters. In all 5 reported patients therapy with single ureteral stents had failed despite correct stent position. With the increased stiffness of 2 parallel ureteral silicon 7F Double-J stents ureteral kinking and luminal compression could be reduced leading to sufficient reduction of hydronephrosis. This approach with potential space between the stents preserves urinary flow through as well as around the stents which is considered to be the most important mechanism in stented ureters. In cases of extrinsic ureteral obstruction with failure of a single stent the simultaneous use of 2 parallel Double-J ureteral stents should be taken into account as a technically easy therapeutic option. It may obviate percutaneous nephrostomy tube placement or more invasive therapy.     

Ureteral metal stents: a tale or a tool?

There are four types of ureteral metal stents: self expandable, balloon expandable, covered, and thermoexpandable shape-memory. Insertion of metal stents requires expertise with transurethral and percutaneous techniques. The stricture is traversed with the aid of a guidewire via a percutaneous nephrostomy, and the stenotic segment is dilated using a high-pressure balloon catheter. The stent is then inserted over the guidewire, such that the upper end bypasses the obstruction by at least 3 to 4 cm, while the lower end extends intravesically for 0.5 to 1 cm from the ureteral orifice. If necessary, two or more stents are placed in sequence, overlapping by at least 2 to 3 cm. Metal stents were initially used for the relief of end-stage malignant disease, and their role in the treatment of benign ureteral strictures is still undefined. Patients often complain of abdominal discomfort and mild pain after stent insertion, which soon resolve spontaneously. Hematuria usually stops after a few days and does not necessitate any treatment. Mild urothelial hyperplasia in the stent lumen is common but usually regresses after 4 to 6 weeks. Many authors suggest the use of a double-pigtail catheter for the first 4 to 6 weeks to avoid narrowing of the ureteral lumen. The influence of stents on ureteral peristalsis is a major but poorly documented issue. Encrustation is a significant problem that needs to be addressed. The characteristics of both the patient and the stent influence its likelihood. Migration of coated metal stents was seen in 81% of patients at our center. Virtual endoscopy has recently been introduced as a tool for the follow-up of patients with stented ureters. Further design development is necessary to obtain the ideal ureteral metal stent. In a recent study in female pigs, paclitaxel-eluting metal stents engendered less inflammation and hyperplasia of the surrounding tissues.     

Nephrovesical subcutaneous stent: an alternative to permanent nephrostomy

PURPOSE: We studied whether a subcutaneous ureteral bypass may be an alternative to a permanent nephrostomy tube in patients with ureteral obstruction caused by pelvic malignancy. MATERIALS AND METHODS: Using local anesthesia we inserted an especially designed nephrovesical stent into subcutaneous tissue. The stent consists of 2 J stents that are joined by a connector after insertion into the renal pelvis and bladder. RESULTS: In 8 patients 10 subcutaneous stents were inserted instead of a permanent nephrostomy tube. Nephrostomy was required because of obstructed ureters caused by metastatic prostate or invasive bladder cancer. Attempted Double-J stent insertion into the obstructed ureter had previously failed. The bypass has functioned well in all cases during 6 weeks to 18 months of followup (mean 5.5 months). CONCLUSIONS: The high complication rate of a permanent nephrostomy tube and frequent rehospitalization render the subcutaneous stent an important alternative to nephrostomy. The subcutaneous stent eliminates external devices for urine drainage and improves patient quality of life.     

New bioabsorbable polylactide ureteral stent in the treatment of ureteral lesions: an experimental study

OBJECTIVE: To evaluate the suitability of a new biodegradable double-helical spiral self-reinforced poly-L,D-lactide copolymer (SR-PLA 96; L/D ratio 96/4) stent as a device for ureteral stenting in respect to changes in kidney function during the biodegradation process. MATERIALS AND METHODS: Sixteen dogs were used as experimental animals and were subdivided into two groups of eight. In Group A, both ureters were cut transversally, sutured, and stented. The right ureter was stented using an SR-PLA 96 stent, whereas a double-J C-Flex stent was used on the left side. Cystotomy was performed at 6 weeks to remove the double-J stents. In Group B, the right ureter of each dog was cut and stented in similar manner using an SR-PLA 96 stent, whereas the left ureters served as untreated controls, and cystotomy was not performed. Serum creatinine and nitrogen values were measured, urine was analyzed for signs of infection, and renal function was evaluated by urography and renography examinations preoperatively and at 6, 12, and 24 weeks postoperatively, at which time points, the dogs were euthanized and the ureters dissected to find persistent SR-PLA 96 particles and macroscopic local changes. There were no urinary tract infections found during the study. RESULTS: In the SR-PLA 96-stented ureters, obstructive hydronephrosis and stricture formation were observed in two cases (11%), with distal displacement of the SR-PLA 96 stent in another case (5.5%). In two additional renal units, a temporary prolongation in the kidney washout time was observed at 6-week renogram examinations. In the C-Flex-stented ureters, temporary changes in renography studies were observed in three cases (37.5%) at 6 weeks. Kidney washout times were protracted at 6 weeks in the pigtail-stented ureters in Group A as a sign of a pressure rise in the renal pelvis secondary to the direct connection between the renal pelvis and bladder, whereas pressure remained normal in SR-PLA 96-stented ureters. In Group B, renal function remained normal after ureteral repair in SR-PLA 96-stented ureters compared with the controls. CONCLUSIONS: The double-helical apical stent design offers some advantages over a double-J design. The risk of pressure-induced kidney damage is lowered, because there is no direct connection between the bladder and renal pelvis, and the risk of upper urinary tract infections is reduced. The biodegradation of the device necessitates the removal of the stent. These preliminary results suggest that a biodegradable SR-PLA 96 stent with more effective expansion capacity can be used for stenting after a ureteral repair.     

Self-expanding metallic ureteral stents for treatment of ureteral stenosis after kidney transplantation

The incidence of post-renal transplantation ureteral stenosis ranges from 2%-12%. Because the role of self-expanding ureteral metallic stents for its treatment has been scarcely reported, the aim of this study was to evaluate the efficacy of Nitinol stents. Eleven ureteral stenoses in patients with chronic graft dysfunction (8 cases) or high surgical risk (3 cases) were treated by antegrade percutaneous implantation of Nitinol stents through a nephrostomy tract. The mean follow-up period was 48 +/- 7 months (range, 3-85 months). The patency rate at the moment of return to dialysis, death, or last check-up was 73% (8/11). Three patients (27%) developed stent occlusion. Two patients were treated using a trans-stent double-J catheter and 1 patient using stent removal and pyeloureterostomy using the native ureter. The mean percentage decrease in serum creatinine (Cr) level after stent implantation was 41% (range, 14%-63%). Nitinol ureteral stent implantation is an effective alternative for the treatment of ureteral stenosis in patients with chronic graft dysfunction or high surgical risk.     

Outcomes of indwelling metallic stents for malignant extrinsic ureteral obstruction

Objectives

To report the treatment outcomes of patients with extrinsic ureteral obstruction treated with metallic stents and to identify the factors predicting stent failure.

Methods

A total of 52 patients with extrinsic ureteral obstruction as a result of malignancy (66 ureters) were treated with metallic stents (Resonance^®) and included in the study. The median observation period was 118 days.

Results

The median survival time of these patients was 210 days, and the stent patency rate was 86.0% at 6 months and 60.0% at 1 year. Eight (15.4%) patients underwent nephrostomy as a result of stent failure. The occlusion rate of bilateral ureteral obstructed cases was significantly higher than that of unilateral cases. There was no correlation between the preoperative serum creatinine level, causes of ureteral occlusions (compression by tumor, lymph node metastasis, peritoneal dissemination), obstructed site (upper, middle, lower ureter) and stent failure.

Conclusions

Metallic stents are excellent in maintaining patency compared with the conventional stents. Therefore, they can be used as first‐line treatment of malignant ureteral obstructions.     

Externally coated ureteral metallic stents: an unfavorable clinical experience

OBJECTIVE: The purpose of the present study was to evaluate the use of externally coated stents in patients with malignant ureteral obstruction. MATERIALS AND METHODS: We have prospectively evaluated 16 patients, 10 men and 6 women, with malignant ureteral obstruction treated successfully by placement of Passager metal stents (Boston Scientific, Natick, MA, USA) bypassing the stricture. Mean patient age was 65.6 years (range 62-78 years). Ureteral patency was confirmed 24 and 48 hours by injection of contrast material through the nephrostomy tube, and after patency confirmation the nephrostomy catheter was removed. RESULTS: All stents were positioned successfully, and the postoperative course was uneventful. In 13 cases (81.2%) the prostheses finally migrated into the bladder hindering overall ureteral patency (mean time of migration: 1.5 months). Patency was achieved in the remaining ureters (n=3), during the follow-up period (mean: 8 months, range 6-16 months), without any need for further intervention. CONCLUSION: The inappropriate anchorage and the increased ureteral peristalsis are the main causes of migration towards the bladder, thus, minimizing the usefulness of this stent for the treatment of ureteral strictures.     

Drainage and antireflux characteristics of a biodegradable self-reinforced, self-expanding X-ray-positive poly-L,D-lactide spiral partial ureteral stent: an experimental study

PURPOSE: To evaluate the drainage and antireflux characteristics of a new self-expandable self-reinforced poly-L,D-lactide partial ureteral stent (SR-PLA 96) in an experimental model. MATERIALS AND METHODS: Twelve dogs were used as experimental animals. A low-midline laparotomy and cystotomy were performed on all animals. In group A (six animals), 50-mm long SR-PLA 96 ureteral stents with a double-helical spiral design were inserted into both ureters, leaving the lower ends 2 cm above the ureterovesical junction. In group B (six animals), both ureters were stented with traditional pigtail stents (C-Flex) Double-J; Cook Urological), which were removed 8 weeks after surgery. Renal function and ureteral patency were evaluated by dynamic kidney imaging and urography examinations at 6 and 12 weeks postoperatively. The degrees of vesicoureteral reflux at two levels of the ureters and at the level of the renal pelvis were evaluated by nuclear voiding cystograms at 6 weeks. RESULTS: The partial SR-PLA 96 stent design showed more favorable antireflux properties that the Double-J stent design. The degree of vesicoureteral reflux, reflected in an increase of nuclear enhancement at 6 weeks, was lower in the distal (7.9% +/- 14.7% v 63.2% +/- 17.3%; P < 0.05) and middle (6.1% +/- 8.1% v. 45.5% +/- 19.5%; P = 0.15) levels of the ureters as well as at the level of the renal pelvis (-3.4% +/- 3.6% v 6.2% +/- 3.9%; P = 0.65) than in the Double-J-stented ureters. No significant differences in renal function or ureteral patency were observed at 12 weeks after the Double-J stents had been removed and the SR-PLA 96 stents had fragmented. CONCLUSION: A self-expandable, self-reinforced SR-PLA 96 partial ureteral stent showed more favorable antireflux properties than a Double-J stent.     

Ureteral metallic stents: Application of virtual endoscopy for ureteral patency control

OBJECTIVE: In the present study we have applied virtual endoscopy (VE) in patients with ureteral metallic stents as a follow-up tool study especially in the need to define ureteral patency. METHODS: We performed the suggested technique in 6 patients with malignant ureteral obstruction treated successfully by placement of Wallstent intraureteral metallic stents, and correlated the results with antegrade nephrostomography 48 hours after initial stent placement. RESULTS: In 2 patients restenosis was observed, and in the remaining 4 patients the stented ureters remained patent during the follow up evaluation. VE and antegrade nephrostomography, were concurrent as to their findings. Moreover, VE proceeds beyond the stenotic segment, allowing visualization of the ureteral lumen both cephalad and caudal to the point of obstruction. CONCLUSION: VE is providing indeed a more accurate, direct and dynamic approach in the evaluation of a strictured ureteral lumen within the metallic stent.     

The morphological, in situ effects of a self-reinforced bioabsorbable polylactide (SR-PLA 96) ureteric stent; an experimental study

PURPOSE: The present study was done to evaluate the biocompatibility of a new biodegradable double helical spiral self-reinforced poly-L, D-lactide copolymer (L/D ratio 96/4, SR-PLA96) ureteric stent. MATERIALS AND METHODS: In sixteen dogs, the right ureter was cut transversally, sutured and stented with a 50 mm. long SR-PLA 96 stent. In eight dogs, left ureter was similarly operated and stented with a double-J pigtail stent (C-Flex, Cook Urological Inc.), while eight remaining ureters served as plain controls. Urine was analyzed for signs of infection. The dogs were terminated at 6, 12 and 24 weeks postoperatively and the ureters dissected to find persistent SR-PLA 96 particles or local ureteric changes. Histologic samples were taken at three levels of dissected ureters in contact with the stent. RESULTS: C-Flex and SR-PLA 96 materials were well tolerated. Both of these induced only minimal ureteral wall edema, epithelial hyperplasia, epithelial destruction and inflammatory cell reaction. In SR-PLA 96 stented ureters the tissue reaction subsided after the degradation of the device. CONCLUSIONS: SR-PLA 96 spiral stent is regarded highly compatible and SR-PLA 96 might be a suitable material for a partial ureteric stent. Biodegradation of a SR-PLA 96 stent makes stent removal unnecessary.     

Metallic stents for malignant and benign ureteric obstruction

OBJECTIVE: To report our experience of using metallic stents to treat ureteric obstruction caused by malignant or benign disease. PATIENTS AND METHODS: Nine patients with obstruction in 11 ureters caused by malignant or benign disease (mean age 61 years, range 35-82, mean follow-up 7 months, range 3-11) were treated using metallic stents. A balloon-expandable metallic stent was used in one patient and self-expandable metallic stents in the remaining eight. All stents were inserted via a percutaneous antegrade approach. RESULTS: Of the 11 ureters, nine remained patent with no further manipulation during the follow-up of 3-11 months. An additional stent was placed in continuity with the first in two ureters of two patients at 4 and 5 weeks after the first procedure because of persistent obstruction. After the second intervention, their obstruction was improved. Transient vesico-ureteric reflux occurred in two of three stented distal ureters, but the reflux resolved spontaneously within 2 months after stent implantation. Ureteric patency was maintained in all patients and no major complications related to stenting occurred during the follow-up. Two patients died from cervical cancer at 3 and 5 months after stenting. CONCLUSION: In patients with difficult ureteric obstructions a metallic stent provides a safe and effective alternative to an indwelling double-pigtail catheter or percutaneous nephrostomy.     

Polyurethane internal ureteral stents in treatment of stone patients: morbidity related to indwelling times

The morbidity and complications associated with use of internal polyurethane ureteral stents in a series of 290 stone patients treated endourologically or with extracorporeal shock wave lithotripsy were retrospectively reviewed. Of the 299 stents retrieved 141 were also tested for patency to relate the rate of luminal blockage with stent caliber, indwelling time and clinical evidence of obstruction in the stented tract. Stent indwelling times ranged from a few days to 18 months: 11.3% were indwelling longer than 6 months and 1.9% were lost to followup. Incrustation occurred in 9.2% of the stents retrieved before 6 weeks, 47.5% indwelling 6 to 12 weeks and 76.3% thereafter. In 19 cases over-all (6.4%) an auxiliary procedure was required to decrease incrusted stone burden and enable stent retrieval. Other complications included stent migration (3.7%), infection (6.7%) and breakage (0.3%). Despite a 30% rate of luminal blockage in stents retrieved after indwelling times up to 3 months, the incidence of clinical obstruction in stented tracts up to 3 months was 4%, confirming other reports that significant urine flow occurs around rather than through hollow, vented stents. Our findings underline the importance of restricting the use of stents to stone patients who will be reliable at followup. Morbidity was minimal if stent indwelling times did not exceed 6 weeks.     

Noninvasive assessment of patency of internal ureteral stent: role of colour Doppler ultrasound

OBJECTIVE: To compare colour Doppler ultrasonography (CDU) and retrograde cystography in the assessment of the patency of internal ureteral stents. PATIENTS AND METHODS: Thirty-two patients with 33 internal ureteral stents were evaluated for patency of the internal ureteral stent using both CDU and retrograde cystography. Real-time ultrasonography and CDU were performed before retrograde cystography. Stent patency was defined as seeing flow from the distal end of the stent in the urinary bladder or iodinated contrast in the renal pelvis. The two investigators had no prior knowledge of the other's results. After completion of both investigations, stent patency was proved by direct inspection of the stent after removal. RESULTS: Both investigations showed the same result in 27 of the 33 stents. Stent patency was found if either investigation was positive. The accuracies of retrograde cystography, CDU and both were 73%, 79% and 85%, respectively. CONCLUSIONS: CDU is a noninvasive method with high accuracy. Detection of flow at the distal end of the stent is helpful, but absence of flow may or may not indicate an obstructed stent and further investigation should be performed.     

Fluoroscopy guided retrograde ureteral stent insertion in patients with a ureteroileal urinary conduit: method and results

PURPOSE: We evaluated retrograde double pigtail stent placement in patients with ureteroileal anastomosis. MATERIALS AND METHODS: Procedures were performed under digital C-arm fluoroscopic guidance and the patient under sedation analgesia. Radiography of the conduit was done to delineate urinary diversion anatomy and identify ureteral reflux. A purpose designed, angled tip catheter was used to direct a straight glide wire across the ureteroileal anastomosis. The glide wire was exchanged for a stiff guide wire for stent placement. We retrospectively evaluated the clinical records of 7 men and 5 women with a mean age of 54.3 years in a 7-year period. In 11 patients a new stent was placed because of ureteroileal stricture in 5, anastomotic leakage in 3, ureterolithiasis in 2 and recurrent malignancy in 1. RESULTS: New stent placement was successful in 10 of the 11 patients (90.9%, 13 of 16 ureters or 81.3%). Stent placement was successful in the 8 ureters in which reflux was noted on radiography of the conduit and in 5 of the 9 (55.6%) in which no reflux was noted. Stent replacement was accomplished in all 22 ureters (6 patients) in which it was attempted. Mean radiological screening time for new stent placement was 13.3 minutes (range 4.7 to 19.7), while for exchange it was 6.4 minutes (range 0.8 to 15.1). There were no immediate complications. CONCLUSIONS: This technique represents a useful approach to the ureter and should be considered an alternative to percutaneous nephrostomy and surgical revision. The approach is also useful for other ureteral procedures, including stone or migrated stent retrieval.     

Therapy of extrinsic ureteral obstruction with 2 parallel ureteral Double-J stents

We present our experiences with the approach of placing 2 parallel ureteral Double-J stents simultaneously in extrinsically obstructed ureters. In all 5 reported patients therapy with single ureteral stents had failed despite correct stent position. With the increased stiffness of 2 parallel ureteral silicon 7F Double-J stents ureteral kinking and luminal compression could be reduced leading to sufficient reduction of hydronephrosis. This approach with potential space between the stents preserves urinary flow through as well as around the stents which is considered to be the most important mechanism in stented ureters.     

Ureteral expanding stent: a new device for urolithiasis

BACKGROUND AND PURPOSE: We investigate a ureteral stent with radially expanding baskets producing passive dilation of the ureter for passage, capture, and removal of small ureteral stones. PATIENTS AND METHODS: Polyurethane ureteral stents were slit to open 15 to 17 baskets along the length. The baskets are designed to dilate the ureter passively and capture stones 相似文献   

Ureteral drainage with the Gibbons indwelling ureteral stent (author's transl)]

The technique of endoscopically placing the Gibbons indwelling stent into the obstructed ureter is described. This technique offers several advantages, especially in managing poor-risk patients whose ureters are obstructed: 1. endoscopic placement of the ureteral stent is associated with less morbidity and mortality than supravesical diversion; 2. quality of life is much less reduced than in supravesical diversion; 3. it is readily reversible; 4 the ureteral stent does not interfere with subsequent operation and offers several advantages over PVC-splints and other materials used for long term ureteral drainage. The placement of an indwelling stent sometimes causes technical problems but complications are rare. 21 Gibbons indwelling ureteral stents have been placed in obstructed ureters of 16 patients at the age of 25--74 years. Our technique, indications, results and complications are described herein.     

Ureteric obstruction in stented renal transplants

The use of renal stents in renal transplants is becoming increasingly popular and has been routine practice at this institution for the past 4 years. Despite this procedure, however, obstruction of the transplant ureter still occurs and we describe 7 patients who developed renal obstruction in the presence of a stented transplant ureter. The underlying causes of these findings are discussed together with suggested recommendations for optimum radiological assessment of transplant ureteric stents. The implication of these observations is that urine may flow down stented ureters between the ureter and the stent rather than down the stent lumen.