Covered retrievable expandable nitinol stents in patients with benign esophageal strictures: initial experience

PURPOSE: To investigate the safety and clinical effectiveness of covered retrievable expandable nitinol stents in 25 patients with a benign esophageal stricture. MATERIALS AND METHODS: Under fluoroscopic guidance, covered retrievable expandable nitinol stents were placed in 25 patients with a benign esophageal stricture and were removed with a retrieval hook 1-8 weeks later. RESULTS: Stent placement was successful in all patients, with no procedural complications. After stent placement, all patients could ingest solid food. The stents were successfully removed from all but two patients. One patient passed the stent via the rectum, and the other regurgitated a high cervical stent. After stent removal, one patient developed a small esophagobronchial fistula, which spontaneously sealed within 1 week of stent removal. After stent removal or migration, all patients could ingest solid food. During follow-up (mean, 13 months; range, 2-25 months) after stent removal or migration, 12 patients maintained their improvement in dysphagia and needed no further treatment. Thirteen patients with recurrence were treated by means of repeat balloon dilation. CONCLUSION: Use of retrievable expandable nitinol stents seems to be a safe and effective method of treatment in selected patients with benign esophageal strictures.     

Comparison of temporary and permanent stent placement with concurrent radiation therapy in patients with esophageal carcinoma

PURPOSE: To assess the clinical effectiveness of temporary metallic stent placement with concurrent radiation therapy in patients with esophageal carcinoma by comparing it with permanent stent placement with concurrent radiation therapy. MATERIALS AND METHODS: Covered retrievable expandable nitinol stents were placed in 47 patients with esophageal carcinoma 1 week before starting radiation therapy; the stents were electively removed 4 weeks after placement in 24 patients (group A), while not electively removed in the other 23 patients (group B). In cases of complications, the stents were also removed from patients in groups A and B. The dysphagia score, complications (severe pain, granulation tissue formation, stent migration, esophagorespiratory fistula, and hematemesis), tumor overgrowth/regrowth, reintervention rates, and dysphagia-progression-free and overall survival rates were compared in the two groups. RESULTS: Stent placement or removal was technically successful and well tolerated in all patients. The dysphagia score was significantly improved in both groups after stent placement (P < .01). Each of the stent-related complications was less in group A than in group B but there was no significant difference. However, the total number of patients with one or more than one complications and who needed related reinterventions was significantly less in group A than in group B (P = .042 and .030, respectively). Tumor overgrowth/regrowth and the total number of patients who required related reinterventions was not significantly different (P = 1.00 and .517, respectively). Dysphagia-progression-free and overall survival rates were significantly longer in group A than in group B (P = .005 and .001, respectively). CONCLUSION: Temporary placement of a covered retrievable expandable metallic stent with concurrent radiation therapy for patients with esophageal carcinoma is beneficial for reducing complications and related reinterventions and for increasing resultant survival rates compared with permanent esophageal stent placement.     

Treatment of tracheobronchial obstruction with a polytetrafluoroethylene-covered retrievable expandable nitinol stent

PURPOSE: To evaluate the clinical effectiveness of polytetrafluoroethylene (PTFE)-covered retrievable expandable nitinol stents in tracheobronchial strictures. MATERIALS AND METHODS: With fluoroscopic guidance, PTFE-covered retrievable expandable nitinol stents were placed in 15 symptomatic patients with benign (n = 6) or malignant (n = 9) tracheobronchial strictures. Complications and improvement in respiratory status were evaluated. Stents were removed electively 6 months after placement in benign strictures or if complications occurred. Membrane degradation or separation from the wire mesh was evaluated in removed stents. RESULTS: A total of 17 stents were successfully placed and were well tolerated in all patients. Sputum retention, stent migration, and tissue hyperplasia occurred in 23.5% (n = 4), 17.6% (n = 3), and 17.6% (n = 3) of stents, respectively. A total of 11 stents were successfully removed electively 6 months after placement (n = 4) or when complications occurred (n = 7). All 11 such stents were removed without difficulty with use of standard techniques, antecedent balloon dilation being necessary in two cases as a result of tissue hyperplasia. No removed stent showed signs of membrane degradation, and two removed stents showed signs of membrane separation from the mesh. CONCLUSIONS: PTFE-covered retrievable expandable nitinol stents were effective in the treatment of tracheobronchial strictures. Stent removal was easy with use of standard techniques, and no removed stent showed evidence of membrane degradation.     

Results of temporary placement of covered retrievable expandable nitinol stents for tuberculous bronchial strictures

Covered retrievable expandable nitinol stents were successfully placed in nine patients with tuberculous bronchial strictures refractory to balloon dilation. Complications included stent migration (n = 1) and tissue hyperplasia at the proximal portion of the stent (n = 2). During the follow-up period (5-52 months), stricture recurred in three of five patients (60%) after temporary stent placement for 2 months, whereas stricture did not recur in the other four patients after temporary stent placement for 6 months. Temporary placement of covered retrievable stents appears to be an effective method for the treatment of patients with tuberculous bronchial strictures refractory to balloon dilation.     

Recurrent traumatic urethral strictures near the external sphincter: treatment with a covered,retrievable, expandable nitinol stent--initial results

PURPOSE: To investigate the clinical effectiveness of a covered, retrievable, expandable nitinol stent in treating traumatic urethral strictures near the external sphincter. MATERIALS AND METHODS: The stent was 10 mm in diameter when fully expanded and 40-50 mm long. To make it removable, two nylon drawstrings were attached to its lower inner margin. Twelve consecutive men (19-67 years; mean age, 47 years) with traumatic urethral strictures near the external sphincter that were refractory to endoscopic urethrotomy were treated. With fluoroscopic guidance, a stent was placed to completely bridge the external sphincter. The stent was electively removed with a retrieval hook wire 2 months after placement. Stent placement and removal were successful in all patients, with no procedural complications. RESULTS: Mean maximum urine flow rate was 5 mL/sec (range, 3-7 mL/sec) before stent placement and 27 mL/sec (range, 16-40 mL/sec) at 1 week after placement. During the mean follow-up of 20 months (range, 2-37 months) after the first stent removal, strictures recurred in eight of 12 patients. For the eight patients with recurrence, a second stent was placed and 4 months later was removed from seven of the eight patients. During the mean follow-up of 18 months (range, 4-32 months) after the second stent removal, strictures recurred in two patients, in whom a third stent was placed and then removed 4 months later, with good results. Four (33%) of 12 patients, five (62%) of eight patients, and two (100%) of two patients were successfully treated with placement of the first stent, the second stent, and the third stent, respectively. In the remaining patient, the second stent remains in place. CONCLUSION: Placement of a covered, retrievable, expandable nitinol stent seems to be effective in treating urethral strictures near the external sphincter and warrants further investigation.     

Temporary placement of covered retrievable expandable nitinol stents with barbs in high-risk surgical patients with benign prostatic hyperplasia: work in progress

Purpose

To report the use of a newly constructed, covered, retrievable, expandable nitinol stent with barbs to overcome the problem of stent migration associated with conventional covered prostatic expandable stents and to evaluate prospectively the technical feasibility and clinical effectiveness of the stents in patients with benign prostatic hyperplasia (BPH).

Materials and Methods

A covered retrievable expandable nitinol stent with four barbs was placed with use of an 18-F stent delivery system in seven consecutive patients with symptomatic BPH who had high operative risks. Age range of patients was 62–83 years (mean 74 years). In cases in which the stent migrated, it was replaced with a stent with eight barbs. The stents were routinely removed 4 months after placement using a 21-F stent removal set.

Results

Stent placement was technically successful and well tolerated in six of the seven patients. The remaining patient needed a second stent placement after removal of the first stent. The stent with four barbs migrated into the urinary bladder in four patients (57%); three of these patients received a second stent with eight barbs with good results, and the fourth patient did not need further treatment because his symptoms improved. Routine removal of the stent 4 months after placement was performed in three of the seven patients with good results.

Conclusions

Retrievable stents with eight barbs seem to overcome the problem of stent migration associated with conventional prostatic expandable stents. Preliminary results suggest that stents with barbs are both feasible and effective in patients with BPH.     

Malignant esophageal-tracheobronchial strictures: parallel placement of covered retrievable expandable nitinol stents

Purpose: To assess the safety and clinical effectiveness of the parallel placement of covered retrievable expandable metallic stents in the palliative treatment of malignant esophageal and tracheobronchial strictures.

Material and Methods: Under fluoroscopic guidance, parallel stents were placed in 12 symptomatic patients with both malignant esophageal and tracheobronchial strictures. Seven of these 12 patients also had an esophagorespiratory fistula (ERF) and one patient had an esophagocutaneous fistula. Technical success, clinical improvement, complications, and survival rates were evaluated.

Results: A total of 28 esophageal and airway stents were successfully placed. The grade of dysphagia and dyspnea score significantly decreased after stent placement (P = 0.002 and 0.003, respectively). ERF and esophagocutaneous fistula were sealed off in all eight patients after esophageal stent placement; however, the esophagocutaneous fistula reopened 1 month later. Complications included stent migration or expectoration (n = 3), tracheal compression by the esophageal stent (n = 3), new fistula development due to covering membrane degradation of the esophageal stent (n = 1), and symptomatic sputum retention (n = 1). Stent removal was easily performed for two stents; one migrated stent and the other with covering membrane degradation. All 12 patients died within the mean survival period of 72.50 days (range 7-375 days).

Conclusion: Parallel placement of covered retrievable expandable metallic stents is safe and effective for the palliative treatment of malignant esophageal and tracheobronchial strictures.     

暂时性食管支架成形术治疗儿童食管良性狭窄

目的 评价儿童食管良性狭窄使用暂时性食管支架成形术治疗的疗效.方法 儿童烧灼性食管狭窄及食管术后吻合口狭窄患儿10例,支架置入前均先行食管吞钡检查,吞咽评分为3,并置入覆膜可回收支架.结果 支架置入后,所有患儿无明显并发症,并安全回收.支架置放期间所有患儿能进食固体食物,无吞咽困难.支架取出后6～12个月随访,患儿均能正常进食,吞咽评分为0.结论 应用暂时性支架成形术治疗儿童食管良性狭窄安全、有效.     

Malignant tracheobronchial strictures: palliation with covered retrievable expandable nitinol stent

PURPOSE: To evaluate the safety and clinical effectiveness of a covered retrievable expandable nitinol stent for the treatment of malignant tracheobronchial stricture and/or esophagorespiratory fistula (ERF). MATERIALS AND METHODS: With fluoroscopic guidance, stents were placed in 35 symptomatic patients with malignant tracheobronchial stricture and/or ERF in most cases caused by lung or esophageal cancer. The site of stricture was most commonly at the trachea or left main bronchus. If there were complications, the stent was removed with a retrieval set. Nine patients had combined symptomatic ERF. RESULTS: A total of 47 tracheobronchial stents were placed and were technically successful and well-tolerated in all patients. Improvement of dyspnea was achieved in 92% of the patients (24 of 26 patients). Associated ERF in nine patients was effectively treated with tracheobronchial stent placement with or without esophageal stent placement. Stent migration, tumor overgrowth, symptomatic sputum retention, and hemoptysis occurred in 17% (6/35), 6% (2/35), 20% (7/35), and 17% (6/35) of patients, respectively. There were no documented cases of tumor ingrowth. Stent removal was performed easily in five patients when stent migration (n = 2), severe pain (n = 1), tumor overgrowth (n = 1), or persistent gastrobronchial fistula (n = 1) developed. All patients died 2 days to 26 weeks (mean, 9.62 weeks) after stent placement because of disease progression (n = 18), pneumonia (n = 9), hemoptysis (n = 5), or unknown cause (n = 3). CONCLUSION: Use of a covered retrievable expandable nitinol stent is a safe and effective method for relieving dyspnea. This procedure contributed to improved quality of life for patients with malignant tracheobronchial stricture and/or ERF. Stent retrievability was useful in resolving stent-related complications.     

Renal cyst pseudoenhancement: evaluation with an anthropomorphic body CT phantom

PURPOSE: To evaluate the feasibility of using a retrievable urethral stent and to evaluate whether granulation tissue resolves after stent removal in a canine urethra. MATERIALS AND METHODS: Polyurethane-covered retrievable 0.10-mm-thick (n = 11) or 0.15-mm-thick (n = 10) nitinol wire stents were placed in the urethras of 20 dogs. In one dog, a second stent was placed in the urethra because of complete migration of the first stent into the urinary bladder. The stents were removed with retrieval hook wires 4 weeks (n = 10) and 8 weeks (n = 10) after placement. Fourteen dogs were sacrificed just after stent removal, and the other six dogs were sacrificed 2 weeks after stent removal. Information concerning procedure success, stent migration, and tissue response was obtained. RESULTS: Stent placement was technically successful in all dogs. Follow-up urethrograms showed partial (n = 4) or complete (n = 1) stent migration. Stent removal failed in two dogs due to partial or complete migration. Granulation tissue was observed at both ends of the stent in 17 dogs. Urethrograms and urethral specimens obtained 2 weeks after stent removal showed diminished granulation tissue and decreased thickness of the papillary projections of the epithelium compared with results obtained immediately after stent removal. CONCLUSION: Although some design modifications are necessary to reduce current complications, the polyurethane-covered retrievable nitinol stent seems feasible for use in the urethra. Stent-induced granulation tissue formation improved after stent removal.     

Covered metallic stent placement in the management of cervical esophageal strictures

PURPOSE: To describe the authors' experience with self-expandable covered metallic stents in 16 patients with malignant and benign cervical esophageal strictures. MATERIALS AND METHODS: Sixteen expandable covered metallic stents were placed with fluoroscopic guidance in 16 patients (14 men, two women; mean age, 60 years; age range, 26-75 years) with malignant and benign strictures of the cervical esophagus. The causes of strictures were ingestion of corrosive agents (n = 3), biopsy-proved squamous cell carcinoma (n = 12), and postsurgical scarring (n = 1). The mean dysphagia scores at presentation were compared with those after stent placement by using the Wilcoxon signed rank test. RESULTS: Stent placement was technically successful in all patients. The reduction in the mean dysphagia score after stent placement was statistically significant (P = .0327). All patients complained of mild to severe foreign body sensation, with four reporting severe pain necessitating immediate stent removal. With the exception of one patient with limited follow-up, complications requiring intervention occurred in all patients, including migration in nine patients and tissue hyperproliferation in two. Of the 12 patients with a malignant stricture of the esophagus, four patients eventually underwent gastrostomy for the placement of a feeding tube and one patient underwent surgery. All four patients with a benign cervical stricture failed to achieve long-lasting improvement with temporary stent placement. CONCLUSIONS: Although the placement of covered metallic stents in the cervical esophagus provides adequate initial palliation, it is associated with poor patient tolerance and a high complication rate.     

Obstruction of the lacrimal system: treatment with a covered,retrievable, expandable nitinol stent versus a lacrimal polyurethane stent

PURPOSE: To compare the clinical effectiveness of a covered nitinol stent with that of a polyurethane stent for treatment of lacrimal system obstructions. MATERIALS AND METHODS: A nitinol stent was knit from a single thread of 0.1-mm nitinol wire in a tubular configuration and was covered by dipping the stent into a polyurethane solution. The stent was 4 mm in diameter and 30 or 35 mm long. With fluoroscopic guidance, a covered nitinol stent (n = 33, group A) or a polyurethane stent (n = 35, group B) was placed in 68 patients. The following items were evaluated retrospectively: technical success, procedure time, cumulative patency rate, and complications. An unpaired Student t test was used to analyze the difference between the procedure times. Kaplan-Meier survival curves and a log-rank test were used to compare the cumulative patency rates. RESULTS: Stent placement was technically successful in 31 (94%) of 33 patients in group A and in all 35 (100%) patients in group B. After stent placement, all patients showed resolution of epiphora. Average procedure time was 400 seconds (range, 270-900 seconds) in group A and 260 seconds (range, 150-900 seconds) in group B. The difference between the procedure times was statistically significant (P =.0003). During the mean follow-up period of 40 months, there was recurrence of epiphora in 30 of 31 patients in group A and 26 of 35 patients in group B. The difference of the cumulative patency rates was statistically insignificant (P =.2). CONCLUSION: Although the polyurethane stent used for treatment seemed to be more effective than the nitinol stent, selection of these stents for placement should be made with caution, because the long-term patency rates are not encouraging.     

How to design the optimal self-expandable oesophageal metallic stents: 22 years of experience in 645 patients with malignant strictures

Objectives

To evaluate the clinical efficacy and safety of self-expandable metallic stent (SEMS) placement for malignant oesophageal strictures and their relationship with stent designs.

Methods

Seven generations of SEMS were used to treat 645 consecutive patients with oesophageal strictures. Logistic regression models were constructed to identify predictive factors associated with complications.

Results

Stent placement was technically successful in 641 of 645 patients (99.4%). The clinical success rate was 95.5%. There were 260 (40.3%) complications after stent placement. Due to complications, 68 stents were removed; 66 of 68 stents (97.1%) were removed successfully. Stainless steel (SS) stents (odds ratio [OR] 4.18; 95% confidence interval [CI] 2.10, 8.32) and radiation therapy (RT) before stent placement (OR 4.23; CI 2.02, 8.83) were significantly associated with severe pain. Flared ends (OR 9.63; CI 3.38, 27.43), stricture length <6 cm (OR 2.01; CI 1.13, 3.60), and a stent diameter <18 mm (OR 3.00; CI 1.32, 6.84) were predictive factors of stent migration. Polyurethane membranes were associated with more frequent tumour ingrowth than polytetrafluoroethylene (PTFE) membranes (P?=?0.002).

Conclusions

Despite the relatively high complication rate, retrievable self-expandable PTFE-covered nitinol stents equipped with a head and a tail appeared to be an effective treatment for malignant oesophageal strictures.

Key Points

? Self-expandable metallic stents are now widely used for palliating unresectable oesophageal strictures ? Stents equipped with a head and a tail showed decreased stent migration rate ? Stainless steel stents and radiation therapy before stenting can cause severe pain ? Polyurethane membranes were associated with more frequent tumour ingrowth than polytetrafluoroethylene membranes ? Considering the high complication rate, stent retrievability is important for safety reasons     

Malignant gastric outlet obstructions: treatment by means of coaxial placement of uncovered and covered expandable nitinol stents

PURPOSE: To assess whether coaxial placement of uncovered and covered expandable nitinol stents overcomes the disadvantages of the increased migration rate seen with covered stents and the tumor ingrowth seen in uncovered stents in the treatment of malignant gastric outlet obstructions. MATERIALS AND METHODS: Two types of expandable nitinol stent were designed: an uncovered stent and a covered stent. Under fluoroscopic guidance, the uncovered and covered stents were placed coaxially with complete overlap in 39 consecutive patients with malignant gastric outlet obstruction caused by stomach cancer. Food intake capacity was graded on a scale of 0-4. Stent patency rate was estimated by the Kaplan-Meier method. RESULTS: Technical success rate was 97% (38 of 39 patients). After stent placement, food intake capacity improved at least one grade in 36 patients. Stent migration occurred in three patients (8%), that is, partial (n = 2) or complete (n = 1) upward migration of the inner covered stent into the stomach. Two of these patients were treated by placement of an additional covered stent. During the mean follow-up period of 134 days (range, 15-569 d), 10 patients developed recurrent symptoms of obstruction with tumor overgrowth being the most common cause. Nine underwent placement of an additional covered stent with good results. The median period of primary stent patency was 157 days (mean, 278 d). The 30-, 60-, and 180-day patency rates were 97%, 91%, and 39%, respectively. Four patients (10%) died within 1 month after the procedure. CONCLUSION: Coaxial stent placement technique seems to contribute to decreasing the migration rate of the stent and decrease the rate of recurrent obstruction by preventing or delaying tumor ingrowth.     

Bronchial stump fistula :treatment with covered retrievable hinged metallic stents-preliminary clinical experience

Objective To evaluate the preliminaily clinical efficacy and retrievability of a retrievable hinged covered metallic stent in the treatment of the bronchial stump fistula （BSF）. Methods Between April 2003 and March 2005, 8 patients with bronchial stump fistula after pneumonectomy or lobectomy were treated with two types （A and B） of retrievable hinged covered metallic stents. Type A stent was placed in 6 patients and type B in 2 under fluoroscopic guidance. The stent was removed with a retrieval set when BSF was healed or complications occurred. Results Stent placement in the bronchial tree was technically successful in all patients, without procedure-related complications. Immediate closure of the BSF was achieved in all patients after the procedure. Stents were removed from all patients but one. Removal of the stents was difficult in two patients due to tissue hyperplasia. Patients were followed up for 6 - 21 months. Placement of the stents remained stable in all patients except one due to severe cough. Permanent closure of BSF was achieved in 7 （87.5%） of 8 patients. Conclusion Use of a retrievable hinged covered expandable metallic stent is a simple, safe, and effective procedure for closure of the BSF. Retrieval of the stent seems to be feasible. （J Intervent Radiol, 2007, 16： 253-257）     

Bronchial stump fistula: treatment with covered, retrievable, expandable, hinged stents--preliminary clinical experience

Purpose: To evaluate the preliminary clinical efficacy and retrievability of a covered, retrievable, metallic hinged stent in the treatment of bronchial stump fistula (BPF).

Material and Methods: Between April 2003 and March 2005, eight patients with bronchial stump fistula after pneumonectomy or lobectomy were treated with two types of covered, retrievable, metallic hinged stents. Type A stent was placed in six patients and type B in two under fluoroscopic guidance. The stent was removed with a retrieval set when BPF was healed or complications occurred.

Results: Stent placement in the bronchial tree was technically successful in all patients, without procedure-related complications. Immediate closure of the BPF was achieved in all patients after the procedure. Stents were removed from all patients but one. Removal of the stents was difficult in two patients due to tissue hyperplasia. Patients were followed for 4-16 months. Placement of the stents remained stable in all patients except one due to severe cough. Permanent closure of BPF was achieved in seven (87.5%) of eight patients.

Conclusion: Use of a covered, retrievable, expandable, metallic hinged stent is a simple, safe, and effective procedure for the closure of bronchial stump fistula. Retrieval of the stent seems feasible.     

Fate of migrated esophageal and gastroduodenal stents: experience in 70 patients

PURPOSE: To investigate the frequency of esophageal and gastroduodenal stent migration and the fate of such stents. MATERIALS AND METHODS: The authors studied five types of covered metal stents. Type A stents were nonretrievable polyurethane-covered stents with shouldered ends (n = 169), type B stents were retrievable polyurethane-covered stents with shouldered ends (n = 62), type C stents were retrievable polyurethane-covered stents with flared ends (n = 72), type D stents were retrievable polytetrafluoroethylene-covered stents with shouldered ends (n = 369), and type E stents were separated stents (n = 216). Types A-D stents were esophageal stents, and the type E stent was a gastroduodenal stent. Stents were placed in 888 patients with either benign (n = 43) or malignant (n = 845) causes of stricture. The rate of stent migration was analyzed relative to completeness of migration, the cause of obstruction, stent type, and stent placement location. The fate of migrated stents and the treatment of patients were evaluated. RESULTS: Stent migration occurred in 70 of the 888 patients (7.9%). Migration occurred in 11 of the 43 patients (25%) with benign cause of strictures and 591 of the 845 patients (7.0%) with malignant cause. The migration rates for types A, B, C, D, and E stents were 10%, 4.8%, 24%, 7.3% and 2.8%, respectively. Of the 70 migrated stents, 45 had complete migration and 25 had partial migration. The anastomotic sites were the areas most commonly associated with migration (16%), but this was not statistically significant. Forty of the 70 migrated stents were removed with retrieval devices under fluoroscopic guidance because they were not passed with stool and possibility of complications related to migrated stents. The remaining 30 stents exited via the rectum (n = 15), remained in the body without complications (n = 12), or were surgically removed because they caused complicated intestinal obstructions (n = 3). CONCLUSION: The overall migration rate for esophageal and gastroduodenal stents was 7.9%. Most migrated stents were removed nonsurgically, exited the body spontaneously, or remained in the body in an uncomplicated state. Surgical stent removal was necessary in three patients (4.3%) due to complicated intestinal obstructions.     

Covered retrievable tracheobronchial hinged stent: an experimental study in dogs.

PURPOSE: To evaluate the safety and technical feasibility of the use of a covered retrievable tracheobronchial hinged stent and investigate the histopathologic airway changes after placement and removal of the stent in dogs. MATERIALS AND METHODS: The experimental stent was composed of tracheal and bronchial stents that were connected together at their ends. Each stent was woven from a single thread of 0.2-mm-diameter nitinol wire filament in a tubular configuration and covered with polyurethane solution by a dipping method. Drawstrings were attached at the upper end of the tracheal stent for stent removal. Under fluoroscopic guidance, 20 stents were placed at the lower trachea and left main bronchus in 20 dogs and were electively removed 4 weeks (n = 10) or 8 weeks (n = 10) after placement. Ten dogs were killed just after stent removal and the remaining 10 were killed 2 weeks after stent removal. RESULT: Stents were successfully placed in all dogs. Pneumonia was observed in three dogs. Stent migration occurred in seven dogs (35%). Except for two cases of stent expectoration, 18 stents were easily removed within a few minutes. There was considerable granulation tissue proliferation and inflammatory reaction in the airways of the dogs that were killed just after stent removal. The pathologic changes of the airways returned to almost-normal conditions 2 weeks after stent removal. CONCLUSION: Placement and removal of a covered retrievable tracheobronchial hinged stent seems to be feasible, and histopathologic changes of the airway related to the stents returned to normal 2 weeks after stent removal.     

Double-Layered PTFE-Covered Nitinol Stents: Experience in 32 Patients with Malignant Esophageal Strictures

We evaluated the effectiveness of a double-layered polytetrafluoroethylene (PTFE)-covered nitinol stent in the palliative treatment of malignant esophageal strictures. A double-layered PTFE-covered nitinol stent was designed to reduce the propensity to migration of conventional covered stent. The stent consists of an inner PTFE-covered stent and an outer uncovered nitinol stent tube. With fluoroscopic guidance, the stent was placed in 32 consecutive patients with malignant esophageal strictures. During the follow-up period, the technical and clinical success rates, complications, and cumulative patient survival and stent patency were evaluated. Stent placement was technically successful in all patients, and no procedural complications occurred. After stent placement, the symptoms of 30 patients (94%) showed improvement. During the mean follow-up of 103 days (range, 9–348 days), 11 (34%) of 32 patients developed recurrent symptoms due to tumor overgrowth in five patients (16%), tumor ingrowth owing to detachment of the covering material (PTFE) apart from the stent wire in 3 (9%), mucosal hyperplasia in 2 (6%), and stent migration in 1 (3%). Ten of these 11 patients were treated by means of placing a second covered stent. Thirty patients died, 29 as a result of disease progression and 1 from aspiration pneumonia. The median survival period was 92 days. The median period of primary stent patency was 190 days. The double-layered PTFE-covered nitinol stent seems to be effective for the palliative treatment of malignant esophageal strictures. We believe that the double-layer configuration of this stent can contribute to decreasing the stent’s migration rate.     

Malignant gastroduodenal obstructions: treatment by means of a covered expandable metallic stent-initial experience

PURPOSE: To investigate the technical feasibility and clinical effectiveness of a polyurethane-covered expandable nitinol stent in the treatment of malignant gastroduodenal obstructions. MATERIALS AND METHODS: The stent was constructed in-house by weaving a single thread of 0.2-mm nitinol wire in a tubular configuration and was covered with polyurethane solution by means of a dipping method. With fluoroscopic guidance, the stent was placed in 19 consecutive patients with malignant gastric outlet obstruction (n = 15) or duodenal obstruction (n = 4). All patients had severe nausea and recurrent vomiting, and their obstructions were inoperable. RESULTS: Stent placement was technically successful in all but one patient. After stent placement, symptoms improved in all but one patient, who had another stenosis at the proximal jejunum. One patient with stent placement in the second portion of the duodenum became jaundiced. During the mean follow-up of 11 weeks, stent migration occurred in five patients 1-4 days after the procedure. All patients with stent migration were treated by means of placing a second, uncovered nitinol stent. Two of these five patients showed recurrence of stricture because of tumor ingrowth; they underwent coaxial placement of a third, covered nitinol stent with good results. CONCLUSION: Placement of a polyurethane-covered expandable nitinol stent seems to be technically feasible and effective for palliative treatment of inoperable malignant gastroduodenal obstructions. Stent migration, however, is problematic and requires further investigation.