Percutaneous insertion of permanent metal stents appears to offer a safe and reasonably effective, minimally invasive technique for long-term patency restoration in patients with extrinsic ureteral obstruction.
The investigators evaluated outcomes for 102 patients (mean age, 59 years) implanted with stents representing a variety of devices from different manufacturers. Ninety patients had a malignant ureteral obstruction and the pathology was benign in 12 patients. Forty patients had bilateral stent placement. Mean follow-up was 15 months for the patients with malignant strictures (range, 8 to 38) and 39 months for the benign stricture group (range, 18 to 72).
Primary patency was analyzed as the primary endpoint and was defined as successful abolishment of the stricture after implantation of the endoprosthesis without the need for any additional intervention. Primary patency was achieved in 94 (66.2%) of the 142 implanted ureters. Secondary interventions were performed in 31 ureters (21.8%).
"The implantation technique involves a short operative time and has been associated with minimal complications. The main problem we have encountered is obstruction relapse as a result of trauma-induced urothelial hyperplasia through the stent mesh into the lumen. In animal studies, we have shown a paclitaxel drug-eluting stent used in interventional cardiology incites less inflammation and hyperplasia, and we will be investigating whether its use provides more durable maintenance of ureteral patency."
Different stent types used
The stents used in the retrospective study included self-expandable and balloon expandable devices. Some were bare metal and others were coated externally or internally. The most commonly used stent was the Wallstent (Schneider, Zurich, Switzerland), which was implanted in 46 patients. The remaining patients received one of six other stents.
Sixteen patients were implanted with the Passager stent (Boston Scientific, Natick, MA), which is an externally coated device. Notably, it was associated with a high rate of migration; in 13 of 16 patients, the Passager stent migrated into the bladder and impeded ureteral patency.
"We were reluctant at first to place these stents in patients with a benign ureteral stricture, but were surprised to find the primary patency rate was somewhat better in those patients than in the group with malignant ureteral obstruction. However, the patency rate achieved in the patients with benign strictures is not yet high enough to justify more widespread use of this approach," Dr. Liatsikos said.
"In conclusion, malignant and/or benign ureteral obstruction can be alleviated by placement of a metal stent. Further experimental and clinical evaluation is deemed necessary to resolve concerns regarding their use, and to define the ideal lining material for metal ureteral stents, thus establishing their safety and efficacy within the ureteral lumen."