Outcomes of studies reviewing patients who have undergone placement of a coil-based metallic ureteral stent indicate it is a viable alternative for management of benign and malignant upper urinary tract obstruction.
Analyses performed by the stent's manufacturer show that an indwell time of 12 months is possible in select patients and may reduce the cost and morbidity of stent changes. However, not all patients achieve this potential benefit of the metallic stent, and it appears that careful monitoring of these patients is critical.
At the AUA annual meeting, Achal P. Modi, MD, reported findings of a series of 39 patients treated using the Resonance stent (Cook Urological, Bloomington, IN) at The Ohio State University Medical Center, Columbus, and Columbia University Medical Center, New York. Renal obstruction was due to malignancy in 29 patients and benign disease in 10; stent placement was unilateral in 20 patients and bilateral in 19.
Dr. Modi reported that among 31 renal units that had been switched to the metallic stent after obstructing the polymer stent, 13 (42%) also obstructed the metallic stent. In addition, encrustation of the metallic stents occurred in three patients at 5, 10, and 11 months, respectively. One patient required cystolitholapaxy and another required a percutaneous nephrolithotomy to break up and remove the stone that had grown on the metallic stents. This problem occurred in individuals without a history of encrustation of their polymer stent, and due to the radio-opaque nature of the metallic stent, the encrustation was difficult to clearly identify on plain x-ray, Dr. Modi noted.
"We believe the metallic stent is a viable alternative to nephrostomy tubes in select patients who failed conventional stents due to malignant or benign ureteral obstruction. However, they are susceptible to inherent stent-related problems so that close follow-up is necessary, especially to detect obstruction in patients with bilateral stents," he said.
During the discussion, Dr. Modi acknowledged that experience with the metallic stent is too preliminary to identify factors predicting failure. Anecdotally, he offered the impression that the metallic stent appeared to be more successful in patients with benign versus malignant disease.
Cost benefits observed
Consistent with this observation, urologists from Loyola University Medical Center, Maywood, IL, reported positive experience with the metallic stent in 13 patients (15 stents) with benign ureteral obstruction, most often due to ureteropelvic junction obstruction (54%).
Twelve patients (92%) maintained adequate drainage and had no significant change in serum creatinine. The single failure was a patient with a ureteral tortuosity whose stent obstructed at 6 months in association with new onset of hydronephrosis and elevated creatinine. Three stents were removed earlier than 12 months, two because of irritative voiding symptoms not responding to medical therapy and one because of gross hematuria. Metallic stents changed after 12 months showed no significant encrustation or complications, reported Hector L. Lopez-Huertas, MD, a fellow in endourology at Loyola working with Thomas Turk, MD, and colleagues.
An analysis of stent cost maintenance over 12 months also was conducted and showed a benefit of the metallic stent. The mean cost of a single stent change was higher for the metallic stent than for the polymer device ($8,446 vs. $7,676), reflecting the higher direct cost of the metallic stent. However, due to the extended dwell time of the metallic stents, the average cost of stent maintenance per year was almost twofold higher for the polymer versus metallic stent ($23,999 vs. $13,605).
"We believe the metallic stents are a feasible, safe, and cost-effective alternative for managing benign ureteral obstruction in patients who are not candidates for definitive repair," Dr. Lopez-Huertas said.
A co-author of the Ohio State/Columbia study is a consultant/adviser and lecturer for Cook Medical.