HISTOLOGICAL-CHANGES ASSOCIATED WITH LONG-TERM URETHRAL STENTS

Objective To assess the histological changes found in patients with lo ng-term external sphincter, prostatic and urethral stents. Patients an d methods Eighteen patients with long-term stents (mean time since ins ertion 3.5 years) were investigated. Three had external sphincter sten ts for detrusor-sphincter dyssynergia secondary to spinal injury, eigh t had prostatic stents for obstruction secondary to benign prostatic h yperplasia and seven had urethral stents for recurrent strictures, Nin e stents were occluded at investigation, of which seven were entirely removed. The mucosae overlying the remaining two were biopsied, as wer e mucosae over the nine patent stents, at urethroscopy. Results The ch anges observed included polypoid hyperplasia (11 of 18 patients) betwe en and around the stent mesh wires, nonkeratinizing squamous metaplasi a (two) or hyperkeratotic squamous metaplasia (seven), chronic inflamm ation (15) with prominent plasma cell infiltrates (11), variable forei gn-body granuloma (two) and microabscess formation (five), usually ass ociated with clefts formed around the stent wires (three of five). Con clusion Stents become incorporated into the urethral wall by a process of polypoid hyperplasia through the stent mesh, with at least focal c overing of the stent in most cases, and with variable inflammatory inf iltrates, most of which are rich in plasma cells. The urothelial and c onnective tissue proliferation resulted in obstruction of the stent lu men in nine of the patients studied, Further long-term study is necess ary to exclude the development of carcinoma in patients with keratiniz ing squamous metaplasia, although no malignancy was seen in this study .