What must one do who frequently experiences a brownish fluid discharge accompanied by flatulence, which contaminates the undergarments, causing him difficulty in performing prayers?

Liquid stool expelled with gas is excused according to the Maliki school due to hardship if it occurs daily, even once. Therefore, ritual ablution (ghusl) is not required every time, and prayer is valid despite its presence. As for the emission of gas, if it is continuous such that it does not stop for a sufficient time to perform purification and prayer, then the ruling of سلس (incontinence) applies to it.