Metallic better than polymeric stents for CUO management

The use of Resonance metallic stent (MS) for chronic ureteric obstruction (CUO) leads to markedly longer indwelling time that prevents the higher unit cost of the stent when compared with the conventional polymeric stent (PS), reports a study in Singapore.

“It has potentially reduced the number of procedures and operations patients have to undergo, with a well-tolerated 12-month dwell time without significant encrustation,” the researchers said. “Hence, it should be considered for all patients with CUO requiring long-term ureteric drainage, regardless of the underlying aetiology.”

Clinical data, including outcomes for all ureteric stents inserted for long-term management of CUO from all causes from 2014 to 2017, from 63 patients with CUO being treated at the National University Hospital in Singapore were obtained for this study. The researchers then retrospectively reviewed and compared these data between the MS and PS episodes.

Overall, 247 stents were placed in CUO patients over the 4-year study period, of which 45 were MSs. No significant differences were observed in all baseline characteristics between the MS and PS groups, except for the aetiology of obstructive cause. [Singapore Med J 2025;66:28-32]

The MS, however, had significantly longer mean indwelling stent duration than PS (228.6 vs 146.1 days; p<0.001), resulting in lower average number of stent changes per year in the MS group than the PS group (1.4 vs 6.3 times).

Although the unit cost of MS was higher than that of PS, no significant difference was noted in the mean cost overall (cost per dwelling day SGD 7.82 vs 8.23; p=0.888).

“[R]esonance MS is a better option than PS to manage CUO from malignant and benign causes, regardless of self-payee or co-payee healthcare systems, because its significantly longer indwelling time mitigates the higher unit cost of the stent,” the researchers said.

Management options

Managing CUO remains a challenge since the upper urinary tract obstruction arising from malignant or benign causes can be addressed by several management options. These courses of action include percutaneous nephrostomy tube placement, ureteric stenting, and surgical repair, with different pros and cons of each modality.

“The Resonance ureteric stent is an MS with reportedly high tensile strength and a flexible coil that resists extrinsic compression and is approved by the US Food and Drug Administration to last for up to 12 months,” the researchers said. “The above study supports current available evidence of its patency durability in patients with malignant or benign CUO.” [BMC Urol 2017;17:16]

Insertions of stent were deemed to be less complicated in MS when compared with the conventional PS for CUO. In terms of function, the MS has a failure rate ranging from 21.4 percent to 37 percent in previous studies. This is slightly higher than that seen in the current analysis. [J Endourol 2010;24:1189-1193; J Urol 2011;185:2217-2222]

Disease condition

One other challenge in CUO management is the wide spectrum of disease conditions. For instance, an earlier study by Goldsmith and colleagues reported an increased risk of MS failure in patients with evidence of prostate cancer invading the bladder during stent placement. [J Urol 2012;188:851-855]

Likewise, a study by Liatsikos and colleagues found a higher patency failure in benign CUO in patients with stone disease, ureteroenteric and iatrogenic ureteroscopic strictures.

"We have correspondingly reported good outcomes when using MS for benign CUO due to strictures secondary to chronic inflammatory conditions and retroperitoneal fibrosis,” the researchers said. “Hence, with increasing reported experience, the use of MS can be individualized to various CUO conditions, which optimizes their patency duration rates to further improve cost-effectiveness.”