The principal aim of this pilot study is to directly compare both approaches and analyze the failure rate after one year of follow-up. These data will serve as the basis to design a larger phase II or III trial in the future with failure rate as the primary end-point. Other study objectives are thoroughly described underneath.

Urethral stricture disease can occur throughout the entire length of the male urethra and has a wide variety of potential etiologies1. The standard treatment for this condition is urethroplasty, an open reconstructive procedure aiming to restore urethral patency1.

Urethroplasty covers a wide variety of surgical techniques and can be performed in a single stage or in multiple stages1. The latter option is generally reserved for patients with a very challenging disease1 (often including very dense fibrosis and poor local tissue conditions) and is most commonly performed for urethral strictures in the penile urethra2.

In case of a multi-stage urethroplasty, the first stage generally involves opening the urethra longitudinally over its diseased segment and suturing the urethral edges to the edges of the skin1. After that, a period of urethral rest of at least 3 months is foreseen after which the second stage procedure is performed by tubularizing the urethral plate around a transurethral catheter and closing the dartos layer and skin over the reconstructed urethra1. When the urethral plate is too narrow or of too poor quality to allow retubularization, the urethral plate is incised on the midline and a graft is sutured into the defect in order to augment the urethra enough to allow for retubularization after all1.

This dorsal inlay procedure can be performed during the first or second stage1. To the best of our knowledge, there are no studies that directly compare the outcomes of both approaches and consequently, there is no clear guidance for surgeons as to whether the graft should be administered during the first or second stage of the procedure. Also, there are absolutely no data available to use in a power analysis for a randomized controlled trial investigating this matter.

Against this background, the principal aim of this pilot study is to directly compare both approaches and analyze the failure rate after one year of follow-up. These data will serve as the basis to design a larger trial in the future with failure rate as the primary end-point. Other study objectives are thoroughly described underneath.

Inclusion Criteria:

• Voluntarily signed written informed consent according to the rules of Good Clinical Practice (Declaration of Helsinki) and national regulations.
• Age ≥ 18 years.
• Male patient.
• Fit for operation, upon surgeon's discretion.
• Isolated penile stricture that requires a multi-stage urethroplasty with dorsal inlay of a graft (upon surgeon's discretion).
• Use of oral mucosa as graft material.
• Patient is able and willing to comply with protocol.
• Prior urethral surgery (dilation, urethrotomy of urethroplasty) is allowed.

Exclusion Criteria:

• Absence of signed written informed consent.
• Age < 18 years.
• Female patients.
• Transgender patients.
• Patients unfit for operation.
• Stricture disease extending beyond the penile urethra or concomitant stricture at a different urethral segment.
• Use of graft other than oral mucosa.
• Any condition or situation, which, in the investigator's opinion, puts the patient at significant risk, could confound the study results, or may interfere significantly with the patient's participation in the study.
• Unwilling or unable to comply with study protocol.
• Patients deciding not to undergo the second stage will be excluded post-hoc.
• When the surgeon intra-operatively decides to carry out a single-stage procedure after all, the patient will also be excluded post-hoc.
• If the surgeon decides that no graft is needed to retubularize the urethra, the patient will also be excluded post-hoc.
• If the surgeon decides that a two-stage Bracka repair is needed, where the urethral plate is entirely cut away during the first stage and grafted, the patient will also be excluded post-hoc.

Upon reasonable request.

Upon request only

Participants cannot be blinded because of the nature of the surgery. Treating surgeon cannot be blinded. Blinding of outcome assessors, data analysts and authors of the manuscript was considered, but lifted due to practical considerations.