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 I 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).Meatal 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 the anastomosis 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. AIM: To investigate the possibility of urethral reconstruction with a free colonic mucosa graft and to present our preliminary study with urethral substitution using a free graft of colonic mucosa for treatment of 7 patients with complex urethral stricture of a long segment. METHODS: Ten female dogs underwent a procedure in white the urethral mucosa was totally removed andreplaced with a free graft of colonic mucosa.Aurodynamicstudy was performed before the operation and sacrifice.The dogs were sacrificed 8 to 16 weeks after the operation for histological examination of urethra.Besides, 7 patients with 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 previousuccessfully 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 I dog. The resul tsof urodynamic studies showed that the difference in the maximum 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 10 experimental dog .Plicae surface and unilaminar cylindricepithelium of the colonic mucosa was observed in dogssacrificed for 8 weeks after the operation. The plicae surface and 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 patientswerefollowed up for 3-18 months postoperatively (mean 8.5 years) .Meatal 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 withUrinary 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 the anastomosis sites has been observed on urethroscopy in 4patients over 6 months after operation. CONCLUSION: Urethral mucosa can be be replaced by colonic mucosa without damaging the continence mechanism infemale dogs.Colonic mucosa graft urethral substitution is a feasible procedure for the treatment of complex urethralstricture of a long segment. The technique may be considered more conventional options have failed or arecontraindicated.