Double JJ Ureteral Stenting: Encrustation and Tolerabilit
Double JJ ureteral stenting for an obstructed kidney was first formally described by Finney in 1978. Ureteric stents are still commonly used in the perioperative management of urolithiasis. The European Association of Urology (EAU) guidelines support ureteric stenting after ureteroscopy in cases with a higher risk of complications. Examples include cases in which there are residual fragments, perforation, bleeding, or associated infection, and patients with single kidneys. Routine pre-stenting is not advised because of the associated morbidity and cost. Despite these guidelines, ureteral stents are commonly used in the perioperative period to avoid stressful emergencies.
Ureteric stents have undergone changes in design and materials to improve their tolerability and reduce the risk of encrustation, two of their biggest drawbacks.
Stent encrustation is an important complication of indwelling ureteric stents and can be associated with infections and obstruction of the collecting system. Furthermore, encrustation can make stent removal difficult, with some cases requiring additional procedures.
The three main factors associated with stent encrustation are: duration of stent exposure to urine; infection or biofilm formation; and the materials that the stent is made of. The duration of exposure to urine is associated with biofilm formation, which in turn predisposes to infection and stent encrustation. A study on stent encrustation demonstrated that encrustation increased with the indwelling time. Only 9.2% of stents with an indwelling time of <6 wk were encrusted, compared to 47.5% of those with an indwelling time of 6-12 wk and 76.3% of those with an indwelling time of >12 wk. Some 93% of the stents removed within 6 wk were patent, compared to 34.7-54.7% of stents removed after 6 wk.
A recent study compared the rate of biofilm formation and encrustation between a hydrocoated silicone stent (Coloplast Imajin hydro) and a Percuflex Plus stent (Boston Scientific) after flexible ureteroscopy for an indwelling time of 20 d. Globally, silicone stents had lower rates of biofilm formation and mineral encrustation in comparison to the Percuflex Plus stents.
In an earlier study, Tunney compared five different stent materials (silicone, Percuflex, silitek, polyurethane, and hydrogel-coated polyurethane) exposed to a model urinary system. All five of the materials developed some encrustation, but silicone stents had significantly less surface coverage at 10 wk when compared to the other four materials studied. Surface coverage for all materials increased with the indwelling time. While the stent material has an impact on the rate of encrustation, this study showed that all stents will encrust if indwelling for long enough.
The stent indwelling time can be monitored by keeping a stent register. One such register uses an electronic extraction reminder that sends automatic e-mails to the responsible clinician to ensure timely stent removal. Major concerns raised regarding such a system include incorrect data entry, which can be improved by using stent barcode technology. When the indwelling stent time is shorter (1 d), the EAU guidelines suggest utilisation of ureteral catheters in place of ureteric stents. Similarly, ureteric stents with strings can be placed if the indwelling time is relatively short, as removal does not require any additional equipment.
Indwelling ureteric stents are associated with significant morbidity in up to 80% of patients: the most common side effects are urinary storage symptoms, flank pain, haematuria, and reduced work capacity. The underlying mechanism is unclear, but possibilities include trigone irritation, ureteric smooth-muscle spasm, and reflux of urine.
A number of design changes to stents have been undertaken to try and improve tolerability. Examples include the development of a dual durometer stent, a biodegradable stent, and a drug-eluting stent, but none consistently led to an improvement in tolerability. The latest innovation is a stent without a bladder coil, which is replaced instead with a suture attached to the stent higher up the ureter, but robust evidence on the effect of this approach is awaited.
Giannarini et al found that one of the most significant factors associated with greater morbidity is the location of the stent distal loop, with a higher risk of postprocedural morbidity among patients whose distal stent loop crossed the midline.
A large multicentre prospective study assessed patient comfort with a hydrocoated silicone stent (Coloplast Imajin hydro) compared to a Percuflex Plus stent (Boston Scien-tific) after ureteroscopy for renal stones. Silicone stents were associated with a statistically significant lower mean body pain index when compared to Percuflex Plus stents at day 20 after the procedure. A lower Urinary Stent Symptom Questionnaire (USSQ) urinary symptoms score was also observed from as early as day 2 after the procedure.
In cases in which indwelling ureteric stents are essential, off-label use of a adrenergic receptor blockers could be considered to reduce unwanted side effects. It is thought that a-blockers act by reducing ureteric smooth-muscle contraction. A meta-analysis of five studies on the effect of a-blockers on ureteric stent-related symptoms showed a reduction in USSQ urinary symptom scores and body pain scores.
Before stenting, all clinicians should consider the guidance on indications for stent placement. When stent insertion is required, minimising the stent indwelling time is important, as this is a significant factor in stent encrustation and symptoms affecting patient quality of life. If possible, when the indwelling time is short, ureteral catheters or stents on strings can be utilised, in line with the current EAU guidelines. It has been found that silicone stents are superior in terms of lower rates of encrustation and stent symptoms, and a-blockers may have an off-label role in reducing both pain and urinary symptoms. Furthermore, an up-to-date stent register may help in ensuring that stents are not forgotten.
Bibby LM, Wiseman OJ, Double JJ Ureteral Stenting: Encrustation and Tolerability. Eur Urol Focus (2020), https://doi.org/10.1016/j.euf.2020.08.014.