Self-expanding metallic stent in the treatment of ureteral obstruction after renal transplantation

Initial Experience in the Use of Novel Auto-expandable Metal Ureteral Stent in the Treatment of Ureter Stenosis in Kidney Transplanted Patients

INTRODUCTION

Ureter stenosis in renal transplantation patients is a relatively frequent complication that negatively conditions graft evolution. The use of ureteral stents is a valid treatment alternative to the use of double-J catheters in patients for whom surgery is not contemplated or after surgical recurrence. We present our initial experience with five patients treated using this technique.

MATERIALS AND METHODS

We describe a total of five patients with ureteral stenosis after renal transplantation who were treated using ureteral stent model UVENTA (Taewoong Medical, Seoul, Korea) in our center. The median follow-up was 18 months (range, 4 to 38 months). We describe the clinical history of patients and previous treatments on ureteral stenosis. The technical procedure of placement is described. The clinical course is analyzed by measurement of renal function and imaging tests, as well as post-stent complications. Survival of the renal graft is evaluated.

RESULTS

The procedure could be completed in all patients without complications. The technique was effective in all patients, with correction of creatinine value and hydronephrosis during the renal ultrasound test. One patient suffered a urinary tract infection episode associated with the use of the ureteral stent. One patient suffered the loss of the renal graft secondary to the development of cryoglobulins. One hundred percent of the ureteral stents are functioning as of the writing of this article.

CONCLUSIONS

In renal transplantation patients with ureter stenosis, metallic stents are a useful technique with low morbidity and associated complications.

Use of Self-Expanding Metallic Ureteral Stents in the Secondary Treatment of Ureteral Stenosis Following Kidney Transplantation

INTRODUCTION

To evaluate the safety and efficacy of self-expanding metal stents in the treatment of ureteral stenosis following kidney transplantation.

MATERIALS AND METHODS

Seven patients who developed benign stenosis after kidney transplantation were treated by a self-expanding metallic stent implantation from June 2007 to March 2014. All patients had undergone at least one open surgical procedure and one endourologic procedure for treatment of the stenosis. The extent of stenosis varied from 1.2 to 3.7 cm. Ultrasonography, urography, diuretic renography, and urine culture were performed every 3 months after stent insertion. Ureteroscopic examination was performed when needed.

RESULTS

Stent placement was technically effective in all cases. The mean operative time was 37 minutes (range, 26-59 minutes). Lower urinary-tract symptoms and the ipsilateral flank pain were common early-stage complications and were greatly relieved after an average of 3 months. The mean follow-up duration was 38 months (range, 13-86 months), and no stent migration or fragmentation was observed. Urothelial hyperplasia occurred in only one patient and was effectively managed with a Double-J stent. Five patients had normal stable renal function; the remaining two had impaired renal function, including one patient with a preoperative renal failure who required dialysis at the end of the follow-up period (36 months).

CONCLUSIONS

As an alternative to open surgery, implantation of a self-expanding metal stent is a safe and effective treatment for ureteral stenosis in patients who have undergone kidney transplantation.

Current status of minimally invasive endoscopic management of ureteric strictures

Endourological techniques are used more often nowadays in the treatment of ureteric strictures of various etiologies. Advances in technology have provided new tools to the armamentarium of the endoscopic urological surgeon. Numerous studies exist that investigate the efficiency and safety of each of the therapeutic modalities available. In this review, we attempt to demonstrate the available and contemporary evidence supporting each minimally invasive modality in the management of ureteric strictures.

Clinical experience with ureteral metal stents

Ureteral metal stents (MSs) present a minimally invasive tool to preserve the drainage of renal pelvis whenever ureteral patency is at risk to be obstructed due to extrinsic or intrinsic etiologies. Clinical experience with these stents demonstrates that they impose a promising alternative treatment option in ureteral pathologies that are difficult to be treated via common polymeric stents. Current application of MSs in the treatment of both benign and malignant ureteral obstruction reveals quite promising results. Nevertheless, the ideal MS that would provide uncomplicated long-term effectiveness is still lucking and current MS usage is facing several adverse effects between which stent obstruction, encrustation, infection, migration, and patient discomfort. Ongoing attempts to create more inert stent with sophisticated novel designs are expected to improve current MS efficiency. MSs will play a major role in the future as a routine management of a variety of ureteral pathologies.

Endourologic implants to treat complex ureteral stenosis after kidney transplantation

OBJECTIVE

To evaluate the safety and efficacy of nitinol stents and the Detour extra-anatomical ureteral bypass graft in treatment of ureteral stenosis after kidney transplantation.

PATIENTS AND METHODS

Eighteen kidney transplant recipients with complex stenosis caused by failure of primary treatment or with high surgical risk or a poorly functioning graft (serum creatinine concentration >2.5 mg/dL) were treated using antegrade percutaneous implantation of nitinol stents (n = 16) or extra-anatomical ureteral bypass grafts (n = 3); 1 patient was treated with both techniques.

RESULTS

Mean (range) follow-up of ureteral stents was 51.2 (3-118) months. Patency rate at last follow-up, resumption of dialysis therapy, or death was 75% (12 of 16 patients). In 4 patients (25%), stent occlusion developed, which was treated using a double-J catheter in 2 patients, stent removal and pyeloureterostomy using the native ureter in 1 patient, and implantation of an extra-anatomical bypass graft in 1 patient. Mean follow-up in patients with extra-anatomical ureteral bypass grafts was 32 (8-64) months. One patient developed a urinary tract infection, and another had encrustation with obstruction.

CONCLUSIONS

Use of nitinol ureteral stents and extra-anatomical ureteral bypass grafts is a safe and effective alternative to surgery for treatment of post-kidney transplantation ureteral stenosis in patients with chronic graft dysfunction, those at high surgical risk, and those in whom previous surgical treatment has failed.

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.

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.

Memokath metallic stent in the treatment of transplant kidney ureter stenosis or occlusion

PURPOSE

To determine the efficacy of the Memokath 051 stent (Engineers and Doctors, Hornbaek, Denmark) in the treatment of recurrent ureteral stenosis or occlusion in transplant kidneys.

METHODS

From October 1985 through January 2004, 1,131 renal transplantations were performed at our center. Four patients who developed recurrent renal transplant ureter obstruction had nephrostomy catheters placed. Antegrade pyelography showed ureteral stenosis in three cases and complete occlusion in one patient. In each case, a Memokath 051 stent was inserted via an antegrade approach. Mean follow-up was 20 months (range 18-21 months). Creatinine levels were measured and ultrasonography was performed during follow-up.

RESULTS

All stent procedures were technically successful. During follow-up, one stent migrated within 10 days after stent insertion and was removed cystoscopically. Another stent had to be removed in the 14th month due to resistant infection, and was replaced with a new Memokath 051 stent which remained patent for another 8 months. The other two stents were fully patent at the 18th and 21st month of follow-up, respectively.

CONCLUSION

Placement of a Memokath 051 stent appears to be a promising treatment alternative to balloon dilation, double-J stents and open surgical intervention for ureteral stenosis or occlusion in kidney transplant recipients. Further study of larger series is necessary.

Long-term results of permanent indwelling wallstents for benign mid-ureteral strictures

BACKGROUND

Benign ureteral strictures are a potentially difficult problem that typically has been solved by open surgery. However, minimally invasive methods would be preferable.

PATIENTS AND METHODS

Three patients with benign ureteral strictures were treated with endoscopic placement of self-expanding permanent indwelling stents (Wallstents). The etiologies of the obstruction were multifactorial and included retroperitoneal fibrosis, stones, traumatic ureteroscopy, ureteral ischemia, and previous open surgery.

RESULTS

One patient died with a functioning stent 1 year, 7 months after placement. The other two patients are doing well 5 years, 2 months and 5 years, 11 months afterward (mean 51 months).

CONCLUSION

Insertion of a permanent indwelling self-expanding ureteral stent is relatively easy, and long-term successes are documented. Placement of Wallstents for benign ureteral strictures should be considered as a treatment alternative.