Does the emission of pus or blood drops from an anal fistula affect the validity of prayer, and what is the ruling on wearing clothes upon which a drop of that blood has fallen for prayer?

Slight amounts of blood, pus, and serous fluid are forgiven in prayer. If the drops that exit are slight, there is no problem. But if they are many, they must be washed from the garment before prayer. However, if these drops exit from the anus after ablution, then purity is invalidated and must be renewed.