Why catheter helps to heal urethral sphincter?

Question

At Surgical Reconstruction of the Urinary Sphincter after Traumatic Longitudinal Disruption they say

In most cases of pelvic fracture injuries including various lesions to the urethra, the placement of a transurethral catheter will allow satisfactory healing of the sphincter mechanism.

Does urine hinder sphincter or other tissues (wall of urethra or bladder or something else) healing, if it is constantly applied to them? (And why?) So, catheter works because it isolates the tissue from urine? Or, maybe, the mechanism of action of catheter is other?

I am not a medic, and I think that urine may leak around catheter and thus make it ineffective, and, that catheter, if applied, widens the channel, pushing sphincter muscles away, separating edges of wound further away from each other, than if there was no catheter, so, makes for them harder to glue and heal. How can you explain these issues, ie how catheter works despite them?

Answer 1

The next sentence of the paper is:

When the whole sphincteric urethral length is involved, it means that the urine diffuses freely into all surrounding tissues. This will mostly result in severe surrounding fibrosis and urethral stricture formation.

You ask if urine hinders healing; yes, fibrosis and stricture formation would impair healing. Note that in the cases described, catheter placement is only one aspect of the treatment, they are also opening existing strictures if necessary and suturing torn tissue back together. The catheter is necessary to separate the healing tissues from urine flow until the healing process has advanced.