Is it necessary to guard against the exit of urine due to inflammation, or is it permissible to move freely and repeat ablution when it exits, and does the exit of a very small amount of urine invalidate ablution?

Prayer must be performed with ablution as long as it is possible. If urine only exits when standing, then you should pray sitting to maintain purity.

As for removing urine from clothes and body: if it is a small amount and difficult to guard against, then its removal is not obligatory and it is excused; changing clothes is not necessary. Otherwise, it must be washed and the clothes changed. Jurists have differed on the amount of urine that is considered a small, excusable amount: - Hanafis: The size of a dirham. - Shafi'is: What cannot be perceived by the average eye, or what is considered a small amount by custom. - Hanbalis: No small amount of impurity is excused at all, especially urine and feces. - Malikis: What is difficult to guard against is excused absolutely to avoid hardship. This opinion is the most preferable and strongest in evidence.