Metal & Long-Term Ureteral Stents
Metal and long-term polymer stents are purpose-designed for extended indwelling time (12+ months) — used in patients with malignant ureteral obstruction, severe recurrent stricture, or those unsuitable for definitive reconstruction who cannot tolerate frequent polymer-stent exchange.
Device Classes
Resonance Metallic Stent (Cook Medical)
- Solid nickel-cobalt-chromium alloy coiled wire — non-patent lumen
- Urine flows around the stent (between the wire and the ureteral wall), not through it
- Indwelling time up to 12 months
- Approved for malignant ureteral obstruction
- Resists extrinsic compression better than polymer stents
Allium URS (Allium)
- Segmental, self-expanding nitinol stent with a polymer cover
- Deploys from a delivery system
- Designed for benign ureteral stricture — remodels with tissue
- Removable
Memokath 051 (PNN Medical)
- Thermoexpandable nitinol spiral — expands with warm saline irrigation
- Used for upper- and mid-ureteral strictures
- Removable with cooling
Silhouette Hybrid Stents
- Hybrid constructions combining metallic reinforcement with polymer surface coating
- Intermediate between polymer and pure metal
Indications
- Malignant ureteral obstruction — pelvic malignancy, retroperitoneal fibrosis, metastatic compression
- Severe recurrent benign ureteral stricture unsuitable for reconstruction
- Radiation-induced ureteral stricture — fibrotic field unsuitable for open reconstruction
- Patients unfit for open/robotic reconstruction but requiring durable drainage
- Palliative drainage in advanced cancer when QoL is the priority
Trade-offs vs Polymer DJ Stents
| Feature | Polymer DJ | Metal / Long-term |
|---|---|---|
| Exchange interval | 3–6 months | 12 months+ |
| Compression resistance | Low (kinks under extrinsic pressure) | High |
| Cost per unit | Lower | Substantially higher |
| Patient-reported symptoms | Moderate-severe stent syndrome | Often milder |
| Encrustation | High with time | Variable (lower for non-luminal designs) |
| Fragmentation risk | Yes with prolonged dwell | Very low |
Limitations
- Cost — many times the cost of a polymer stent per placement
- Encrustation — the Resonance outer surface can still encrust
- Removal — some metal stents are designed for permanent placement; removal attempts risk injury
- Infection — biofilm persists
See also: Double-J Stent, Ureterocolonic Fistula, Vascular-Urinary Fistula — long-indwelling stents in a radiated pelvis are a key risk factor for vascular-urinary fistulas.