A new thermo-expandable shape-memory nickel-titanium alloy stent for the management of ureteric strictures

Objective To assess the ease on insertion, patient tolerance, undesirable s ide-effects, degree of encrustation and duration of upper tract decompressi on with a new thermo-expandable shape memory alloy ureteric stent, Patients and methods From November 1996 to October 1998, 15 patients with u reteric strictures were treated with a new nickel-titanium shape-memory all oy stent, the Memokath 051 (Engineers & Doctors A/S, Hornbaek, Denmark). A total of 22 insertions were carried out. Ureteric obstruction was caused by recurrent colorectal carcinoma in four patients; two patients each with tr ansitional cell carcinoma of the bladder, iatrogenic injury or ischaemia at the uretero-ileal anastomosis; and one patient each with metastatic lymph nodes from prostatic carcinoma, radiation-induced fibrosis, pelvi-ureteric junction obstruction, metastatic carcinoma of the vagina and extra-luminal endometriosis. The stent has a shaft diameter of 9 F and its proximal end e xpands to 17 F. The first three patients were treated with the original ver sion, which expanded to 14 F. The unexpanded stent is inserted into the ure ter after initial dilatation of the stricture to 12 F, The stent is expande d by injection with sterile water preheated to 50 degrees C. The procedures were carried out under a general anaesthetic and patients were allowed hom e the next day. The follow-up protocol included initial intravenous urograp hy (IVU) at 6 weeks, with assessment of a mid-stream urine sample and renal function tests. These were repeated at 3-monthly intervals. Isotopic renog raphy was performed when indicated. Results The mean (range) follow-up was 10.6 (2-21) months; there was comple te relief of upper tract obstruction in all patients. No stent-related symp toms, e.g, pain, sepsis, haematuria or frequency, were noted and no encrust ation has occurred so far. The stent migrated in the first three patients w ith the original smaller diameter of stent but decompression of the upper t racts was maintained. None of the modified wider stents have migrated. The return of peristalsis in the proximal ureter was detected during IVU. There was no apparent endothelial growth through the stent material and no re-ad missions for stent-related complications. Conclusion Early experience with this new stent is very encouraging. All pa tients have maintained satisfactory decompression of their upper tracts wit h no need for repeated hospitalization for stent changes. There have been n o untoward side-effects so far. This stent appears to have a valuable place in the long-term management of ureteric strictures; it is probably most su ited for malignant ureteric obstruction. It should be considered in the man agement of selected benign strictures that require long-term JJ stenting.