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Journal of Peking University (Health Sciences) ›› 2026, Vol. 58 ›› Issue (4): 827-832. doi: 10.19723/j.issn.1671-167X.2026.04.020

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Efficacy of thermo-expandable nickel-titanium alloy ureteral stent placement as maintenance therapy for ureteral strictures

Guowei CHEN1, Zunke XIE1, Lei SHI1, Xuejing GUO1, Junxin WANG1, Ben CAO1, Hao HU2,*(), Lianchao JIN1   

  1. 1. Department of Urology, Beijing Geriatric Hospital, Beijing 100095, China
    2. Department of Urology, Peking University People's Hospital, Beijing 100044, China
  • Received:2026-02-28 Online:2026-08-18 Published:2026-05-19
  • Contact: Hao HU

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Abstract:

Objective: To evaluate the clinical efficacy and safety of thermo-expandable nickel-titanium alloy ureteral stents (Memokath-051) for maintenance therapy of ureteral strictures. Methods: A retrospective analysis was conducted on the clinical data of 16 patients with ureteral strictures admitted to Beijing Geriatric Hospital from January 2024 to April 2025. The cohort comprised 3 males and 13 females, with a mean age of (57.60±9.79) years. Etiologies included post-radiation stricture following abdominopelvic tumor radiotherapy in 13 patients, retroperitoneal fibrosis in 2, and ureteral granuloma in 1. All the 16 patients had experienced failure of previous indwelling double-J stent placement and subsequently underwent conversion to thermo-expandable nickel-titanium alloy ureteral stent insertion. Among the 16 patients, 7 had bilateral ureteral lesions, with a total of 23 ureteral units treated. Operative time, complications (graded according to the Clavien-Dindo classification), stent patency rate, and ureteral stent symptom questionnaire (USSQ) scores were recorded. Follow-up assessments of serum creatinine levels and hydronephrosis improvement were performed 3, 6, and 12 months postoperatively. Results: All 23 stents were successfully placed in the 16 patients (technical success rate, 100%), with a mean operative time of (51.52±9.55) min. The overall stent patency rate 12 months postoperatively was 82.61% (19/23). Early complications occurred in 7 patients. Long-term complications developed in 4 patients, including stent migration (n=1), tissue hyperplasia-induced obstruction (n=2), and stone-related obstruction (n=1); the remaining 5 patients had no complications. Three months postoperatively, serum creatinine decreased from the preoperative baseline of 186.80 (111.80, 244.93) μmol/L to 103.05 (96.20, 135.97) μmol/L (P < 0.01), and hydronephrosis width decreased from 3.20 (2.78, 3.40) cm to 2.05 (1.08, 2.20) cm (P < 0.01). Serum creatinine levels and hydronephrosis remained stable 6 and 12 months postoperatively. Compared with the previous indwelling period of double-J stents, USSQ scores showed significant improvements in urinary symptoms (34.75±2.34 vs. 23.75±3.26), bodily pain (6.50±2.26 vs. 3.00±1.22), general health status, and work performance (all P < 0.001). Conclusion: Placement of thermo-expandable nickel-titanium alloy ureteral stents (Memokath-051) as maintenance therapy for ureteral strictures is safe and effective. Compared with double-J stenting, it improves renal function and hydronephrosis, and enhances patient quality of life. This approach is particularly applicable to patients with long-segment ureteral strictures secondary to post-radiation etiologies.

Key words: Ureteral stricture, Ureteral stent, Thermal-expansion, Nitinol, Minimally invasive therapy

CLC Number: 

  • R693.2

Table 1

General clinical data of 16 patients with ureteral stricture"

Case No. Gender Age/years Laterality Pathogenesis Double J stent duration/months
1 F 56 Bilateral Retroperitoneal fibrosis 24
2 F 46 Left Radiotherapy after cervical cancer surgery 15
3 F 55 Bilateral Radiotherapy after cervical cancer surgery 20
4 F 53 Left Immune-related ureteral granuloma 19
5 F 67 Bilateral Radiotherapy after cervical cancer surgery 3
6 F 52 Left Radiotherapy after cervical cancer surgery 20
7 F 71 Bilateral Radiotherapy after cervical cancer surgery 60
8 M 67 Left Radiotherapy after colon cancer surgery 12
9 M 65 Right Chemoradiation for ureteral carcinoma 4
10 F 30 Bilateral Radiotherapy after cervical cancer surgery 2
11 F 62 Bilateral Radiotherapy after cervical cancer surgery 36
12 F 63 Right Radiotherapy after cervical cancer surgery 19
13 F 61 Right Chemoradiotherapy after cervical cancer surgery 20
14 F 57 Bilateral Chemoradiotherapy after cervical cancer surgery 8
15 F 62 Right Radiotherapy after cervical cancer surgery 54
16 M 66 Left Retroperitoneal fibrosis 10

Figure 1

Procedural steps of Memokath-051 ureteral stent insertion A, retrograde pyelography demonstrating the length of the ureteral stricture; B, deployment of the Memokath-051 stent with its proximal end placed 1 cm above the stricture segment; C, injection of 55 ℃ normal saline to expand the proximal stent into a funnel shape."

Figure 2

Management of intraluminal blood clot obstruction in a Memokath-051 ureteral stent with double-J stent placement and postoperative kidney-ureter-bladder plain film A, blood clot occlusion within the lumen of the Memokath-051 ureteral stent; B, insertion of a 5F/26 cm double-J stent through the Memokath-051 stent; C, kidney-ureter-bladder plain film after placement of the double-J stent inside a Memokath-051 ureteral stent."

Table 2

Complications in 16 patients (23 renal units) undergoing Memokath-051 ureteral stent placement"

Patients Stents Length/cm Complication Clavien-Dindo grade Management
1 1 15 Occlusion Ⅲ Double J stenting in lumen (2 weeks)
1 2 20 Occlusion Ⅲ Double J stenting in lumen (2 weeks)
2 3 25 None
3 4 15 Pain Ⅰ Analgesics
3 5 10 None
4 6 15 Migration Ⅲ Stent replacement
5 7 20 None
5 8 20 None
6 9 15 Stone obstruction Ⅲ Stent replacement
7 10 20 Tissue obstruction Ⅲ Stent replacement
8 11 10 Tissue obstruction Ⅲ Stent replacement
8 12 20 None
9 13 15 None
10 14 25 Fever Ⅱ Antibiotics
10 15 15 Fever Ⅱ Antibiotics
11 16 20 None
11 17 20 Pain Ⅰ Analgesics
12 18 25 None
13 19 25 None
14 20 15 Pain Ⅰ Analgesics
14 21 20 None
15 22 25 Pain Ⅰ Analgesics
16 23 25 Pain Ⅰ Analgesics

Table 3

Comparison of preoperative and postoperative serum creatinine and hydronephrosis"

Items Preoperative 3 months postoperatively 6 months postoperatively 12 months postoperatively χ2 P
Scr/(μmol/L), M (P25, P75) 186.80 (111.80, 244.93) 103.05 (96.20, 135.97) 97.45 (87.18, 124.50) 105.90 (87.08, 126.45) 19.50 ＜0.01
Width of hydronephrosis/cm, M (P25, P75) 3.20 (2.78, 3.40) 2.05 (1.08, 2.20) 1.98 (1.08, 2.10) 1.69 (1.23, 2.30) 27.94 ＜0.01

Table 4

Comparison of preoperative and postoperative USSQ scores"

USSQ domain Preoperative 3 months postoperatively t P
Urinary symptoms 34.75±2.34 23.75±3.26 11.10 ＜0.001
Physical pain 6.50±2.26 3.00±1.22 5.27 ＜0.001
General health status 14.19±1.52 9.37±2.09 7.24 ＜0.001
Work performance 9.06±1.18 4.44±1.09 10.58 ＜0.001
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