Long-term results of permanent metallic stent implantation in the treatment of benign upper urinary tract occlusion

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.

Minimally invasive treatment of ureterovaginal fistula: A review and report of a new technique

Background

An iatrogenic ureterovaginal fistula (UVF) can be a consequence of difficult pelvic surgery. The patient must endure a long wait before having major surgery to reconstruct the injured ureter. Reports that address the minimally invasive treatment of UVF are limited, and are reviewed here. We introduce the concept of using a Memokath™ 051 stent (PNN A/S, Hornbaek, Denmark) as a promising minimally invasive approach for UVF.

Methods

We used PubMed, Science Direct, Google and the Cochrane Library to assemble appropriate evidence-based reference reports. The keywords used for the search were: ‘Memokath’, ‘stent’; ‘ureterovaginal fistula’ and ‘ureteral injury’. The review showed 42 relevant articles published up to September 2011.

Results

Ureteric stenting consistently stopped the vaginal leak of urine. The long-term results were not encouraging after removing the JJ stents at 3 months after insertion. Most patients had a recurrence of the vaginal leak of urine. The outcome was different with the Memokath stent, that remained in situ for a duration far exceeding that of the JJ stent. The Memokath stopped the vaginal leak of urine with no episodes of urinary tract infection and no evidence of stent migration.

Conclusion

Long-term ureteric stenting has two advantages, in that it facilitates urine flow through the ureteric strictured segment down to the bladder, and it stops urine leakage along the fistula. It further promotes the resolution of the ureteric stricture and healing of the fistula. A duration of 3 months was inadequate when a JJ stent was used, whereas longer periods are possible with the Memokath stent. The optimum stenting period required for complete healing of a UVF remains to be defined. Long-term Memokath ureteric stenting can be an effective alternative and minimally invasive approach to conventional surgical repair in selected cases.

Update on ureteral stent technology

Ureteral stents are commonly used in urology but are frequently associated with patient discomfort, stent encrustation and stent-related infection. New biomaterials, coatings and designs have been designed to attempt to reduce these problems. This article reviews coatings to reduce bacterial adhesion and encrustation. In addition, metal ureteral stents, the triclosan and ketorolac drug eluting ureteral stents, and biodegradable ureteral stents are discussed. In summary there is no perfect ureteral stent that avoids all morbidity but there have been significant advances in the last few years in stent technology.

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.

New combined approach in metallic ureteral stenting to avoid urothelial hyperplasia: study in swine model

PURPOSE

We assessed the therapeutic value of a new treatment option for ureteral strictures that may avoid urothelial hyperplasia, which is the main cause of metallic stent failure.

MATERIALS AND METHODS

We used 24 pigs in this study. An experimental model of ureteral stricture was induced in all animals. Obstruction was confirmed by ultrasound and retrograde ureteropyelogram 6 weeks after model creation. The pigs were then randomly allocated to 2 experimental groups. Therapy involved placement of a 6 × 30 mm metallic ureteral covered stent in the ureteral stricture in group 1 and subsequent endoureterotomy at the ureteral segments adjacent to the 2 ends of the stent in group 2. A double pigtail stent was then deployed for 3 weeks. Completion studies 6 months after therapy included retrograde ureteropyelogram, endoluminal ultrasound and ureteroscopy to assess urothelial hyperplasia formation.

RESULTS

At the end of the study evidence of urothelial hyperplasia was seen in 50% of the pigs in group 1 and in 29% in group 2. Four and 2 cases of cranial stent migration in groups 1 and 2, respectively, were seen at 6 months. Hyperplasia and renal involvement were statistically significantly different between the groups with more damage in group 1 than in group 2.

CONCLUSIONS

Hyperplasia was markedly reduced when ureteral peristalsis was inhibited by endoureterotomy at the area of interaction between the stent and the ureter.