title: Is a flared stent effective for decreasing stent migration in canine prostatic urethra?
abstract: BACKGROUND
  Prostatic urethral stents are effective in relieving obstructions caused by benign prostatic hyperplasia (BPH). However, migration of these stents occurs frequently.
  
  
  OBJECTIVE
  To evaluate the efficacy of a flared stent for decreasing the migration rate in comparison with a straight stent in a canine prostatic urethral model.
  
  
  METHODS
  The flared stent (15 mm in diameter and 20 mm in length) was flared up to 19 mm at both ends to prevent migration. A straight stent with the same size was straight without flaring. Both stents were made of a nitinol wire filament and covered with an expanded polytetrafluoroethylene (ePTFE) membrane. The flared stent was inserted in the prostatic urethra of 10 dogs (group 1) and the straight stent in the prostatic urethra of 12 dogs (group 2). Follow-up retrograde urethrography (RUG) was performed 1, 4, and 8 weeks after stent placement. Fisher's exact test was used to compare the migration rate between the two groups. When stent migration occurred during the follow-up period, the same type of stent was inserted again.
  
  
  RESULTS
  Three of 10 (30.0%) flared stents migrated into the urinary bladder between 1 week and 4 weeks after placement. Seven of 12 (58.3%) straight stents migrated into the urinary bladder 1 (n = 3), 4 (n = 1), and 8 (n = 3) weeks following placement. The flared stent group showed lower migration rate than the straight stent group, but the migration rate did not reach statistical significance (P = 0.231). After the second stent placement, one of three (33.3%) flared stents migrated again after 4 weeks and two of seven straight stents (28.6%) after 1 week.
  
  
  CONCLUSIONS
  Although the migration rate was not statistically significant, the flaring of the stent seemed to reduce the migration rate in comparison with straight stents in a canine prostatic urethral model. However, the migration rate of the flared stent was still high, and further developments are required to decrease migration rate.
authors: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea.
authors: Chul-Woong
authors: CW
authors: Woo
authors: Ho-Young
authors: HY
authors: Song
authors: Chang Jin
authors: CJ
authors: Yoon
authors: Tae-Hyung
authors: TH
authors: Kim
authors: Eun-Young
authors: EY
authors: Kim
authors: Jin Hyoung
authors: JH
authors: Kim
authors: Ji Hoon
authors: JH
authors: Shin
mesh_terms: D000497:Alloys; D000818:Animals; D020099:Coated Materials, Biocompatible; D004195:Disease Models, Animal; D004285:Dogs; D004867:Equipment Design; D005500:Follow-Up Studies; D005548:Foreign-Body Migration / Q000209:etiology / Q000517:prevention & control*; D008297:Male; D011138:Polytetrafluoroethylene; D011467:Prostate; D011859:Radiography; D015607:Stents / Q000009:adverse effects; D016896:Treatment Outcome; D014521:Urethra / Q000000981:diagnostic imaging / Q000601:surgery*; D001743:Urinary Bladder / Q000000981:diagnostic imaging
chemical_list: D000497:Alloys; D020099:Coated Materials, Biocompatible; C013616:nitinol; D011138:Polytetrafluoroethylene