AIM: To investigate the possibility of urethral reconstructionwith a free colonic mucosa graft and to present ourpreliminary experience with urethral substitution using a freegraft of colonic mucosa for treatment of 7 patients withcomplex urethral stricture of a long segment.METHODS: Ten female dogs underwent a procedure inwhich the urethral mucosa was totally removed andreplaced with a free graft of colonic mucosa. A urodynamicstudy was performed before the operation and sacrifice.The dogs were sacrificed 8 to 16 weeks after the operationfor histological examination of urethra. Besides, 7 patientswith complex urethral stricture of a long segment weretreated by urethroplasty with the use of a colonic mucosalgraft. The cases had undergone an average of 3 previousunsuccessful repairs. Urethral reconstruction with a freegraft of colonic mucosa ranged from 10 to 17 cm (mean13.1 cm). Follow-up included urethrography, urethroscopyand uroflowmetry.RESULTS: Urethral stricture developed in 1 dog. The resultsof urodynamic studies showed that the difference in themaximum urethral pressure between the pre-operation andpre-sacrifice in the remaining 9 dogs was not of significance(P＞0.05). Histological examination revealed that the colonicfree mucosa survived inside the urethral lumen of the 10experimental dogs. Plicae surface and unilaminar cylindricepithelium of the colonic mucosa was observed in dogssacrificed 8 weeks after the operation. The plicae surfaceand unilaminar cylindric epithelium of the colonic mucosawas not observed, and metaplastic transitional epitheliumcovered a large proportion of the urethral mucosa in dogssacrificed 12 weeks after the operation. Clinically, the patientswere followed up for 3-18 months postoperatively (mean8.5 months). Meetal stenosis was developed in 1 patient 3months postoperatively and needed reoperation. The patientwas voiding very well with urinary peak flow 28.7 ml/s duringthe follow-up of 9 months after reoperation. The otherpatients were voiding well with urinary peak flow greaterthan 15 ml/s. Urethrogram revealed a patent urethra withan adequate lumen with no significant graft sacculation.Neither necrosis of neourethral mucosa nor stenosis at theanastomosis sites has been observed on urethroscopy in 4patients over 6 months after operation.CONCLUSION: Urethral mucosa can be replaced by colonicmucosa without damaging the continence mechanism infemale dogs. Colonic mucosa graft urethral substitution is afeasible procedure for the treatment of complex urethralstricture of a long segment. The technique may be consideredwhen more conventional options have failed or arecontraindicated.