If a person is suffering from urinary incontinence, is his ablution valid?

If the case is as mentioned in the question, then the inquirer is to make ablution and pray before urinating. If not possible, he is to urinate and then wait for some time until the drops of urine exit and then perform ablution and pray; there is no harm if he misses a group prayer. If drops of urine continue to exit until the time of the next prayer enters, he is to make ablution and pray even if drops of urine exit during prayer.

As for madhy (discharge caused by amorous play and kissing) and wady (discharge that exits after urination) exiting after making ablution and praying, the inquirer is to wash the affected area and then make ablution if he wishes to pray.
God the Almighty knows best