ABSTRACT
Introduction
Double-J (JJ) stents are widely used in obstructive uropathy but are associated with encrustation, infection, migration, and the need for repeated exchanges. Metallic ureteric stents such as the Memokath-051 (MMK), in use since 1996, demonstrate high patency rates and efficacy in both benign and malignant ureteric strictures. While prior studies suggest cost-effectiveness over JJ stents, UK-specific data remain limited. This study evaluates the cost-effectiveness, function, and safety of MMK in chronic obstructive uropathy.
Materials and Methods
A retrospective cohort study was conducted of adult patients who underwent MMK insertion between March 2016 and August 2022 for malignant or benign ureteric strictures. Patients with pregnancy, acute sepsis, or acute renal failure were excluded. The primary outcome was cost-effectiveness compared with JJ stent exchanges. Secondary outcomes were stent function and safety.
Results
Twenty-one patients (10 men, 11 women) were included, with a median age of 69 years (range:46–86). Left ureteric stents accounted for 38%, right ureteric in 52%, and bilaterally in 10%. 81% benign obstruction, with the remaining malignant. Stent lengths ranged from 6–15 cm.
After a follow-up of up to 65 months, 52% of patients retained their MMK stent in situ. 20% required removal due to encrustation or haematuria, and 10% experienced spontaneous stent migration. Overall, 70% were successfully managed with MMK. 20% died with the stent in situ (mean duration:15 months). 18% retained stents for >6 months (median: 25 months).
Total cost savings were £42,890 compared with repeated JJ stent exchanges, increasing proportionally with stent dwell time. No MMK-related infections or infection-related admissions occurred.
Conclusion
Memokath-051 is a safe and cost-effective option for chronic obstructive uropathy, with a clinical success rate of 72% and substantial cost savings, particularly in benign strictures. Patients with malignant obstruction may benefit clinically, though shorter stent duration reduces cost-effectiveness.
KEYWORDS: Ureteric stent, memokath, cost effectiveness
Introduction
Ureteric compression or strictures resulting in obstruction of the upper urinary tract are not uncommon in abdominal or pelvic malignancy in both men and women. Most often, it is a sign of disease progression translating to median survival rates of <1 year [1] but can be the presenting feature [2]. The ureter can be intramurally involved or, more commonly, be compressed externally. There can be ischemic fibrosis or strictures of the ureter post-pelvic radiotherapy which equally leads to obstruction of the urinary system [1,2]. The consequences of ureteric obstruction include renal failure and life-threatening infection. It is well recognised that these patients, as a palliative measure, require decompression and maintenance of ureteric patency [1]. Often, a multi-disciplinary approach is taken with regard to decision-making and management of these patients. The patient, depending on the cause, may benefit from more oncological treatment. Therefore, decompression of the upper tracts provides a potential option of chemotherapy that may not otherwise be possible with ongoing obstruction. There are two preferred methods of decompression: ureteric stents and percutaneous nephrotomies [3]. There are advantages and disadvantages to both of these methods. Nephrostomies require external bag to collect urine which can be troublesome for patients to manage with negative impact on their quality of life [4]. Nephrostomy tubes can also fall out, placing strain on interventional radiology services and urology inpatient admissions, making them resource intensive. On the other hand, nephrostomy tube insertion does not require a general anaesthetic to proceed [5] and can facilitate antegrade stents insertion as a long-term alternative. When there is an invasion of the bladder trigone from any prostatic, cervical, or bladder cancer, there is a higher rate of retrograde stent failure, and therefore PCN should be advocated for these patients [5].
Retrograde insertion of ureteric stenting is another option. The main role of the stent is to allow passage of urine and therefore provide decompression to any obstruction system. Matters of concern commonly with stents are encrustation and microbial colonisation, thus leading to urinary tract infection, urinary tract symptoms such as urgency, dysuria, haematuria, and incontinence, stent migration, and misplacement [6]. An ideal stent has been described as ‘easy insertion and removal, easy manipulation, resistance to encrustation and migration, lack of complications, biocompatibility, radio-opacity, bio-durability, affordability (cost-effectiveness), tolerability and optimal flow characteristics’ [6]. Importantly, most used stents require frequent changes under general anaesthesia which comes at a cost to the patient and the health service.
Metallic stents have been used and have proven benefits. Metallic stents exhibit notable resistance to high levels of compression. The market offers a variety of metallic stents, each presenting unique features such as self-expansion, balloon expansion, thermo-expansion with shape memory, covered design, and all-metal double-pigtail configuration. These stents demonstrate effective performance when utilized for long-term urinary drainage. The Memokath-051 stent has been used since 1996, with reported patency rates between 90% and 100%; however, migration rates of 14% to 20% have also been reported. They have had demonstrated benefit in both malignant and benign ureteric strictures [7]
The attractive characteristics of metals, including their ductility, malleability, and ability to be moulded into suitable shapes while maintaining resistance to compression, make them highly suitable for stent materials. In the context of metal ureteral stents, a broader lumen configuration offers improved drainage, thereby facilitating their long-term applicability. Nitinol stands out as a frequently employed material for the fabrication of metallic stents in clinical practice (Memotherm, Memokath 051, Oldenvej, Kvistgaard, Denmark) [8].
Compared to double-J stents, metallic stents offer advantages such as higher patency rates, longer indwelling time, reduced morbidity, and improved ureteric stricture management. However, they have drawbacks including tumour ingrowth, epithelial hyperplasia, difficulty in removing impacted stents, higher cost, and complex insertion. In a Dutch study by Campschroer et al. [9], a 41% patency rate was achieved over 37 months [8].
Limited research has been conducted on comprehensive cost analysis of stenting. In a study involving 10 cases, stenting was found to substantially increase operating time, unplanned doctor visits, and hospital readmissions [10]. Lopez-Huertas et al. compared the costs of metallic stent usage to those of polytetrafluoroethylene (PTFE) stents. The cost analysis revealed a 43% reduction per patient in maintenance expenses associated with polymer stents [11].
The National Institute of Clinical Excellence (NICE) has produced a report [12] which outlined the economic and clinical case for the use of Memokath-051 stents in ureteric obstruction in those individuals with a life expectancy of more than 30 months, who are not suitable for reconstructive surgery and who would otherwise require decompression. Despite this recommendation, it was acknowledged that further outcome data is required to allow for more robust guidance. The most recent review in 2022 [13] again highlighted the need for more data.
There is evidence to suggest that metallic stents, like the Memokath 051 (MMK), are effective methods of managing ureteric obstruction. The cost-effectiveness of metallic stents over JJ stents has been demonstrated in the past; however, there is limited UK data on this. Here, we assess the cost-effectiveness of metallic stents over JJ stents in a UK hospital. We assess the risk of encrustation and duration of MMK stents.
Patients and methods
The Memokath-051 stent is fabricated using a single NiTinol wire and exhibits a funnel-shaped configuration. Initially packaged in a cylindrical form, the shaft of the stent expands to 10.5 FG, while its wider proximal end expands to 22 FG when subjected to a temperature of 55°C. The dual-expansion variant features expanded ends on both sides, reaching a diameter of 22 FG. It can be inserted retrogradely through a cystoscope or antegrade through a nephrostomy tube following tract dilation to 14 FG. These stents are commercially available in fixed lengths of 3, 6, 10, and 15 cm, with the ability to manufacture custom-made longer lengths tailored to individual patient requirements [14].
We performed a retrospective analysis of data retrieved from the trust electronic and paper records of all patients who underwent metallic stent insertion between March 2016 and August 2022. Inclusion criteria were adult men and women who had metallic stent(s) inserted into ureter(s) for ureteric strictures with underlying malignant and/or non-malignant causes. Exclusion criteria were pregnancy and active pelvic malignancy.
The primary outcome was cost-effectiveness of metallic stents insertion at our trust, and the secondary outcome(s) were function and safety of Memokath metallic stents.
NICE selected the Memokath-051 for evaluation in 2018, and an External Assessment Centre (independently body) ran an economic analysis on the Memokath-51 stent [12]. Figure 1 shows the economic model schematic developed by the producers of the Memokath-051 stent [12]. Each point in the schematic was costed by the company, generating a total cost. The EAC generated their own economic model (Figure 2), broadening the cost to the NHS, assessing alternative treatment options, as well as critiquing the parameters of the cost analysis performed by the company. NICE generated their own costings in 2018 and was updated in 2022.
Figure 1.
Economic model schematic developed by the producers of the Memokath-051 stent.
Figure 2.
External assessment centre cost analysis module.
Results
A total of 21 patients underwent ureteric metallic stents insertion between March 2016 and August 2022. The median age was 69 years (range: 46–86). Analysis included data from 10 men and 11 women. Eight patients (38%) had left-sided stents, 11 patients had the sent inserted into right ureter (52%), and 2 (10%) patients had them done bilaterally. There were 4 (19%) patients with malignant ureteric obstruction and 17 patients (81%) with benign underlying causes. The length of the metallic stents used was 6 cm in 10 patients, 8 cm in 3 patients, 10 cm in 5 patients, and 15-cm in 5 patients.
After 65 months of follow-up of the 21 patients, 11 (52%) still have the metallic ureteric stent in situ. Four patients had their stents removed: two stents (10%) were removed due to encrustation, and two were removed due to haematuria. Two stents (10%) fell out of the ureters spontaneously. Therefore, in total 72% of patients were successfully treated with MMK stents. In the current study, we defined MMK failure as encrustation, removal, or replacements due to spontaneous passage. Of the two patients where the stents passed spontaneously, neither required re-stenting. Four (20%) patients died with the stent in situ, where two of them had a malignant underlying cause of ureteric obstruction and two had benign causes. These patients had the stents in-situ for an average of 15 months (range: 5–27) before passing away.
The stent duration ranged from 2 to 65 months. A total of 18 patients had the stent for longer than 6 months (median of 25 months, rang 4–34 months).
Table 1 shows the cost breakdown on MMK versus JJ stent insertion. Table 2 shows the breakdown of patients and their outcomes of stents. For each of these outcomes, there is an average time that the stent was placed for. The cost of the Memokath that was inserted, including follow-up scans and clinics, is also included based on NICE [13] 2022 guidance. The results show that for the 11 patients who still have an MMK in situ, there has been a total of £42,890 saving compared to if the patients were having regular double-J stent exchanges. The value of the MMK stent proportionally increases with the number of months they remain in situ. Hence, the lowest average duration where patients died with Memokath in-situ was 17.75 months; this resulted only a £19 saving compared to if the patients were treated with JJ stents. No patients were admitted to hospital for infection or had MMK-related infections, and therefore no costs were incurred here.
Table 1.
Comparison of cost-effectiveness between Memokath and JJ stents.
| Memokath 051 | Double J Stent | Cost saving per patient | |
|---|---|---|---|
| Total Insertion Cost | £3,217 | £929 | £2,288 |
| Follow-up Cost | £2,567 | £0 | £2,576 |
| Unplanned Replacement Cost | £3,472 | £0 | £3,472 |
| Planned Replacement Cost | £0 | £10,326 | £-10326 |
| Advert Events Cost | £9 | £9 | £0 |
| Total Cost | £9,274 | £11,264 | £-1990 |
Table 2.
The breakdown of patients and their outcomes of stents.
| Outcome | Number | Average time MMK in situ (months) | Total MMK cost, insertion + follow-up | Potential double-J stent exchange saved (average) | Cost if patient had double-J stent for equivalent time (average) |
Potential cost savings due to MMK insertion |
|---|---|---|---|---|---|---|
| Currently in situ | 11 | 47.9 | £58008 | 8 | £100898 | £42890 |
| Spontaneously removed | 2 | 18.5 | £8022 | 3 | £8225 | £203 |
| Haematuria | 2 | 19 | £8065 | 3 | £8397 | £332 |
| Encrustation | 2 | 21.5 | £8280 | 3.5 | £9258 | £978 |
| Died in situ | 4 | 17.75 | £15916 | 3 | £15935 | £19 |
The cost figure of £100,898 reflects the cumulative NHS expenditure associated with double-J stents over the equivalent 47.9-month duration seen in our cohort. While the initial insertion cost (£929) includes consumables and procedural expenses, this figure does not represent the full economic burden. Patients with JJ stents require scheduled replacements every 6 months, resulting in approximately eight further operative episodes in this group. With each replacement, there is a cumulative increase in risk and associated cost due to UTIs reported in 20–30% of JJ stent exchanges, with an average NHS hospital admission cost of £1,042 per episode.
Emergency admission for stent-related pain or obstruction occurring in 15–22% of patients, with an NHS tariff of £1,456–£1,980 per admission. Stent encrustation or haematuria requiring unplanned intervention in 10–15% of cases, each episode costing approximately £2,300.
We perform our cost analysis based the NICE EAG 2022 updated parameters. Figure 3 shows the costing of double-J stenting and the Memokath-051 stenting over a 60-month period (5 years).
These complication-related costs are incorporated into the NICE MTG75 economic model and significantly increase the cumulative cost over time. This is reflected in the higher total (£100,898), which therefore represents not just procedural replacement costs, but the broader economic consequences of multiple interventions, complications and unplanned care.
Discussion
The outcomes of our study suggest that there are direct cost savings to be made from using the Memokath 051 stent in patients with malignant or benign obstruction. There are secondary factors which are not costed but are beneficial to the health service; for example, the 101 theatre slots saved could be used for alternative procedures, therefore reducing waiting list times. The time required for MMK insertion and double-J stent inserted is reported as 45 and 22 min, respectively. Therefore, there is not a large time differential between procedures [12]. There is a reduction in radiation exposure to patients of approximately 12.6 mGy, 2.94 Gy/cm2, and fluoroscopy time of 44.5 s [15]. Finally, there is less chance of patient developing stent-related symptoms and having complications from double-J stents. A study in 2010 by Maan et al. showed that pain, urinary symptoms index, and general health were statistically better in the Memokath group when compared to the double-J stent group. Patients preferred the Memokath stent [14]. Beyond the cost benefit, there is evidence of clinical benefits too [16].
The most recent NICE guidelines (MTG75) [13] show that there is a £1926 cost saving after 5 years but includes the cost of potential replacement of MMK in their cost analysis; here we report no unplanned replacement, and therefore our results show increased cost savings.
It has been noted in previous studies that the cost of the Memokath insertion can be offset if the Memokath stent remains in situ for more than 8–12 months [17]. Our data set shows a higher mean indwelling time compared to other data sets, and some report 11 months to previous data set in the Memokath stents [17]. The EAC reports that the breakeven point for MMK vs double-J stents is at 30 months of stent being in situ, and our mean stent duration was at 29 months. Our results show that there were minimal cost benefits for stents being in situ for less than 17 months. When MMK stents work in patient, as they have done with the 11 patients, the cost benefits continue to grow until 60 months – where manufactures suggest that the MMK should be changed at 60 months. Interestingly, 10 of the 11 patients with MMKs in situ currently are for benign strictures. Patients with malignant strictures tended to die within 2 years of insertion, and therefore the cost benefit is not seen. However, in these patients, seven potential double-J stent procedures were saved, procedures which may not have been possible under anaesthesia because of their deteriorating conditions. Therefore, it may be argued that despite the cost of double-J stenting being favourable in this patient group, it may be preferable to insert MMK stents to prevent repeat anaesthetics or nephrostomies.
Patient selection is therefore critical, and NICE has recently recommended Memokath 051 as an option in individuals with a medium- to long-term survival with malignant stricture. It is also suggested that those who are not suitable for reconstructive surgery or choose not to have it in the benign group, Memokath 051 is a suitable option for these patients too. Its use is also recommended in ‘any type of ureteric obstruction who cannot have or do not want a double-J stent, or when repeat procedures are particularly high risk’. In this patient group, it may not be cost-effective to insert the Memokath stent because their prognosis may be poor; however, it may still offer a better quality-of-life option.
There are alternative metallic stents available for use, such as the Resonance, Allium, and UVENTA stents. Some have shown favourable outcomes with regard to less stent migration compared to the Memokath-051, but the costs of such stents far exceed the MMK. However, comparative studies are scarce, clinical success is not clearly defined, and NICE cites low-quality data in their evidence evaluation [13].
| Study/Source | Design & Intervention(s) | Population & Setting | Follow-up | Key Clinical Outcomes | Patient-Reported Outcomes (USSQ) | Notes/Interpretation |
|---|---|---|---|---|---|---|
| Akbarov [18] (abstract) | Retrospective comparison: Memokath-051 vs internal ureteric replacement (IUR) | 27 renal units (17 pts) Memokath; 27 pts IUR (Germany) |
Mean 42 months | Technical and clinical success reported, but limited detail; complications not fully described | Not reported | Authors describe Memokath as a “niche solution”; very limited data |
| Bolton [19] (abstract) | Case series: Memokath-051 vs Allium | 21 Memokath; 9 Allium (Ireland) |
One-off survey | Limited outcome reporting | USSQ completed by patients; symptom burden acceptable in both stent groups | Small abstract dataset; not powered for comparison |
| Kim [20] | Retrospective comparative: Memokath-051 vs UVENTA | 10 Memokath (14 units), 17 UVENTA (Korea) | Mean 13–14 months | No significant difference in stent survival; migration higher in Memokath group | Not reported | Highlights need for careful insertion technique and patient selection |
| Maan [21] | Cross-sectional QoL comparison: Memokath-051 vs double-J | 18 Memokath vs 23 JJ (UK) | Single post-procedure survey | Not designed to compare long-term survival or complication rates | USSQ showed lower irritative urinary symptoms and better comfort with Memokath compared with JJ | First QoL comparison vs JJ; limited sample; comfort benefit observed |
| Nam 2015 [22] (abstract) | Case series: Memokath-051 vs Resonance | 6 Memokath vs 14 Resonance (Korea) | ~16 months | Clinical success similar; theatre time reported | Not reported | Small sample; malignant obstruction only |
| NCT00166361 trial record (mayo clinic [23]) | Non-randomised prospective comparison: Memokath-051 vs double-J | 14 Memokath vs 10 JJ (USA) | Until removal | Median dwell time ~17 months vs ~4 months for JJ; encrustation reported more frequently with Memokath in supporting data | Not reported | Suggests longer patency with Memokath; small cohort |
| Forster et al. [24] | Real-world cohort, single centre | 100 pts/162 Memokath stents (UK) | Median stent survival 14.5 months; mean FU ~5 years | Overall complication rate 72% (migration ~36–46%, blockage 34%, encrustation 11%, urosepsis 8%); higher complications in benign disease | Not reported | Largest long-term series; emphasises careful patient selection |
| EAC Economic Model (Turner et al. [12]) | NHS cost-effectiveness model: Memokath-051 vs JJ | Modelled | 5-year horizon | – | – | Cost-saving vs JJ after ~30 months; £1.6k–£3.1k saved per patient at 5 years due to avoiding 6-monthly JJ exchanges |
| NICE MTG Update (2022) | Evidence synthesis | Multiple studies | – | Clinical success across studies 43–100%; pooled migration ~18% for Memokath; 0% JJ migration in 2 studies | QoL data included where USSQ used | Recommends Memokath in selected cases requiring long-term stenting |
Conclusions
The Memokath 051 thermo-expandable stent is a cost-effective and safe procedure, and we showed clinical success in 72% of our patients with significant overall cost savings, particularly in patients with benign strictures. Our cost savings were helped in that over the 6-year period, we did not have to replace any stents in our data set. Our data suggests that patients with malignant strictures can be stented successfully; however, they are more likely to have stents in for less time, therefore making it less cost-effective.
Disclosure statement
No potential conflict of interest was reported by the author(s).
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