Tandem Resonance metallic double-J ureteral stents in a single ureter for salvage management of chronic ureteral obstruction

Evaluation of Renal Function and Stent Durability Following Resonance Stent Placement for Benign Disease

Introduction: The metal-based Resonance stent (RS) has traditionally been placed in patients with malignant ureteral obstruction; as such, the long-term utility of RS among patients with benign ureteral obstruction (BUO) remains underinvestigated. Methods: We retrospectively reviewed our database for patients with BUO who underwent RS placement between 2010 and 2020. The impact of chronic RS placement on renal function was evaluated by estimated serum creatinine-based glomerular filtration rate (eGFR), furosemide renal scan, and CT-based renal parenchymal volume measurement. The number of and reason for RS stent exchanges during the follow-up period, incidence of encrustation, and the average indwell time were recorded. A cost analysis of placing the RS vs a polymeric stent was performed. Results: Among 43 RS patients with BUO, at a mean follow-up of 26 months, there was no change in eGFR (p = 0.99), parenchymal volume (p = 0.44), or split renal function of the stent-bearing side on renal scan (p = 0.48). The mean RS indwell time was 9.7 months. Eleven patients (26%) underwent premature stent replacement (6 cases) or removal (5 cases). Stents in 9 patients (32%) were encrusted, of which 4 (44%) required laser lithotripsy. Overall, 25 patients (58%) and 12 patients (28%) had a mean stent indwell time of ≥6 months and ≥12 months, respectively. Placing an RS resulted in a 52%, 37%, and 5.6% cost reduction compared with a regular polymeric stent placement, where it was exchanged every 6, 4, or 3 months, respectively. Conclusions: RS deployment in the patient with a BUO results in cost-effective maintenance of renal function and of renal parenchymal volume at a mean follow-up of 2 years; however, only 28% of patients fulfilled the 1-year criterion for RS indwell time.

REVIEW ON COMPLICATIONS AND ADVERSE EFFECTS OF METALLIC URINARY STENTS

Urinary stents, be it urethral or ureteral, polymeric, metallic or biodegradable, are one of the most frequently used tools in urology and they have been used for decades in prophylactic and therapeutic setting. Although relatively low invasive, they are prone to complications and adverse effects so much that complication rates up to 100% have been described. Many reviews have focused either on specific groups of patients or particular stent types, materials or designs but so far, no comprehensive review on complications has been published. To tackle this issue, a working group was set up within ENIUS (European Network of multidisciplinary research to Improve Urinary Stents) tasked with literature search in order to screen for and systematically review published stent complications in urethra (male only) and ureters (polymeric and metallic ureteral stents in both sexes) when used in obstructed systems. In this paper, we review, catalogue and summarize complications published for metallic urethral and ureteral stents.

Comparative study of renal drainage with different ureteral stents subject to extrinsic ureteral obstruction using an in vitro ureter-stent model

BACKGROUND

To compare the efficacy of different ureteral stents subject to extrinsic ureteral obstruction (EUO), in a controlled in vitro stented ureter experiment.

METHODS

We employ an in vitro ureter-stent experimental set-up, with latex tubing simulating flexible ureters attached to vessels simulating renal units and bladders. The flow behavior of five ureteral stents-polymeric 8F, tandem 6F, tandem 7F, endopyelotomy and metal-was tested under a ureteral deformation configuration of 40°, with 2000 g external force over a 3.5 cm length of the ureter. A constant fluid flow was applied through the ureter-stent configurations, and pressure fluctuations in the renal unit were monitored. We considered a renal unit pressure of 10 cmH₂O or flow discontinuation in the bladder as stent failure. Urine containing debris was mimicked by use of a colloidal solution.

RESULTS

Of all assessed ureteral stents, under EUO conditions, only the single 8F stents remained patent throughout the length of the experiment. All other stents-tandem 6F and 7F, single 7F, metal and endopyelotomy-displayed limitations.

CONCLUSIONS

Tandem and metal stents show no superiority over large luminal polymeric stents for EUO treatment in this in vitro model. Larger luminal stents offer excellent resistance to external pressure and allow adequate colloidal flow. The need for frequent exchange and bladder irritation should also be considered in the choice of stent configuration for treatment of kidney drainage under EUO.