Must one wash the foot and the shoe after doubting whether they were washed following their contamination with urine?

If you doubt that urine has splattered on your leg and shoe, then both are pure, and you are not required to wash them; this is because the default assumption is that they have not been splattered with urine until certainty is achieved otherwise. However, if you become certain that urine has splattered on them, then the area affected by the impurity must be purified.