title: Histological changes associated with long-term urethral stents.
abstract: OBJECTIVE
  To assess the histological changes found in patients with long-term external sphincter, prostatic and urethral stents.
  
  
  METHODS
  Eighteen patients with long-term stents (mean time since insertion 3.5 years) were investigated. Three had external sphincter stents for detrusor-sphincter dyssynergia secondary to spinal injury, eight had prostatic stents for obstruction secondary to benign prostatic hyperplasia and seven had urethral stents for recurrent strictures. Nine stents were occluded at investigation, of which seven were entirely removed. The mucosae overlying the remaining two were biopsied, as were mucosae over the nine patent stents, at urethroscopy.
  
  
  RESULTS
  The changes observed included polypoid hyperplasia (11 of 18 patients) between and around the stent mesh wires, nonkeratinizing squamous metaplasia (two) or hyperkeratotic squamous metaplasia (seven), chronic inflammation (15) with prominent plasma cell infiltrates (11), variable foreign-body granuloma (two) and microabscess formation (five), usually associated with clefts formed around the stent wires (three of five).
  
  
  CONCLUSIONS
  Stents become incorporated into the urethral wall by a process of polypoid hyperplasia through the stent mesh, with at least focal covering of the stent in most cases, and with variable inflammatory infiltrates, most of which are rich in plasma cells. The urothelial and connective tissue proliferation resulted in obstruction of the stent lumen in nine of the patients studied. Further long-term study is necessary to exclude the development of carcinoma in patients with keratinizing squamous metaplasia, although no malignancy was seen in this study.
authors.affiliation: Department of Histopathology, King's College School of Medicine and Dentistry, London, UK.
authors.forename: D M
authors.initials: DM
authors.lastname: Bailey
authors.forename: S J
authors.initials: SJ
authors.lastname: Foley
authors.forename: J P
authors.initials: JP
authors.lastname: McFarlane
authors.forename: G
authors.initials: G
authors.lastname: O'Neil
authors.forename: M C
authors.initials: MC
authors.lastname: Parkinson
authors.forename: P J
authors.initials: PJ
authors.lastname: Shah
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005549:Foreign-Body Reaction / Q000473:pathology*; D006801:Humans; D006965:Hyperplasia; D008297:Male; D008875:Middle Aged; D011470:Prostatic Hyperplasia / Q000628:therapy; D015607:Stents / Q000009:adverse effects*; D014521:Urethra / Q000473:pathology*; D014522:Urethral Diseases / Q000209:etiology / Q000473:pathology*; D014546:Urinary Catheterization / Q000009:adverse effects; D016055:Urinary Retention / Q000628:therapy