What is the correct method of istinja’ (cleaning oneself after urinating or defecating) for women, especially if urine splashes various areas such as the anus and between the labia due to a medical condition, and is it permissible to suffice with toilet paper in this case?

If the impurity exceeds its usual place, it must be washed with water, and it is not sufficient to remove it with a tissue or the like. This is the opinion of Ibn Qudamah, Al-Shafi'i, Ishaq, and Ibn Al-Mundhir. The limit for this is determined by common practice (urf), and Ibn Taymiyyah specified it as the spread of feces to half or more of the inner buttock, and urine to half or more of the glans. The questioner is advised to fear Allah and turn away from obsessive doubts regarding purity.