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?