What is the ruling on a fluid coming out of the anus almost continuously, and sometimes this fluid comes out every time it is washed for ablution?

The event that occurs to the worshipper is considered سلس ( سلس البول or urinary incontinence). The ruling for it is that he should perform ablution for each prayer after its time has begun, and pray with that ablution the obligatory prayer and whatever supererogatory prayers he wishes. He should place a protector on the private part. If anything exits after that, it does not invalidate the ablution nor nullify the prayer.