Smrkolj T et al, 2015: Endoscopic Removal of a Nitinol Mesh Stent from the Ureteropelvic Junction after 15 Years.

Friday, 05 February 2016

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Smrkolj T, Šalinović D.
Department of Urology, University Medical Centre Ljubljana, 1000 Ljubljana, Slovenia.
Clinical Institute of Radiology, University Medical Centre Ljubljana, 1000 Ljubljana, Slovenia.

Abstract

We report a rare case of a patient with a large stone encrusted on a nitinol mesh stent in the ureteropelvic junction. The stent was inserted in the year 2000 after failure of two pyeloplasty procedures performed due to symptomatic ureteropelvic junction stenosis. By combining minimally invasive urinary stone therapies-extracorporeal shock wave lithotripsy, semirigid ureterorenoscopy with laser lithotripsy, and percutaneous nephrolithotomy-it was possible to completely remove the encrusted stone and nitinol mesh stent that was implanted for 15 years, rendering the patient symptom and obstruction free.

Case Rep Urol. 2015;2015:273614. doi: 10.1155/2015/273614. Epub 2015 Dec 1. FREE ARTICLE

Comments 1

Hans-Göran Tiselius on Friday, 05 February 2016 16:34

The authors describe how they successfully removed a Nitinol mesh stent in UPJ after 15 years. The procedure comprised non-invasive as well as invasive methods.

It is of note that when the patient first sought medical advice 6 years after the stent placement, the observed incrustations were left without action. The reasons were probably that the patient was asymptomatic, had symmetric renal function and perhaps also because of shortage of ideas how to handle the problem. Why the patient was examined at that time is not mentioned.

After 7 years (that is one year later) the patient reported symptoms. Attempts to Nitinol stent removal failed and the patient was given an internal double-J stent. After another 4 years the authors finally succeeded to remove the Nitinol stent with a combination of procedures summarized in the report. Eight SWL sessions were part of this procedure together with URS and PCNL.

It is not mentioned in the article what chemical composition that the encrustation had. It is not unlikely, however, that the crystals were composed of infection stone material. If so, initial treatment with SWL and percutaneous chemolytic irrigation with Renacidin would have been an approach that certainly could have facilitated mesh stent removal and reduced the number of SWL sessions and endoscopic procedures.

There are three major lessons learnt from this report:

1. When a Nitinol mesh stent is inserted it is essential to identify risk factors for abnormal crystallization and to take appropriate steps in order to counteract the crystallization propensity.
2. From the experience by the authors of this article it seems essential to place the stent so that it subsequently will be completely covered by epithelium.
3. Regular follow-up of these patients is mandatory and as soon as encrustation is diagnosed it is essential to take necessary steps to solve the problem as early as possible.

The authors describe how they successfully removed a Nitinol mesh stent in UPJ after 15 years. The procedure comprised non-invasive as well as invasive methods.

It is of note that when the patient first sought medical advice 6 years after the stent placement, the observed incrustations were left without action. The reasons were probably that the patient was asymptomatic, had symmetric renal function and perhaps also because of shortage of ideas how to handle the problem. Why the patient was examined at that time is not mentioned.

After 7 years (that is one year later) the patient reported symptoms. Attempts to Nitinol stent removal failed and the patient was given an internal double-J stent. After another 4 years the authors finally succeeded to remove the Nitinol stent with a combination of procedures summarized in the report. Eight SWL sessions were part of this procedure together with URS and PCNL.

It is not mentioned in the article what chemical composition that the encrustation had. It is not unlikely, however, that the crystals were composed of infection stone material. If so, initial treatment with SWL and percutaneous chemolytic irrigation with Renacidin would have been an approach that certainly could have facilitated mesh stent removal and reduced the number of SWL sessions and endoscopic procedures.

There are three major lessons learnt from this report:

1.	When a Nitinol mesh stent is inserted it is essential to identify risk factors for abnormal crystallization and to take appropriate steps in order to counteract the crystallization propensity. 
2.	From the experience by the authors of this article it seems essential to place the stent so that it subsequently will be completely covered by epithelium.
3.	Regular follow-up of these patients is mandatory and as soon as encrustation is diagnosed it is essential to take necessary steps to solve the problem as early as possible.

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