Answer
Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- A man may get plagued with chronic emission of madhi (prostatic discharge) that happens due to medical reasons.
2- Based on this understanding, we would like to state that the rulings pertaining to enuresis are applicable for the emission of prostatic discharge. There is no difference in rulings between them.
Focusing on this issue, we would cite for you the fatwa of Sheikh `Abdullah ibn Jibreen, a prominent Saudi Muslim scholar:
This is considered to be a continual breaking of wudu’ (ablution), like incontinence of urine, so he has to do wudu’ before every Prayer because this is something which breaks wudu’ (ablution), as it is something that comes out of the front passage.
If something comes out while he is praying, he does not need to repeat his Prayer or stop praying because it happened involuntarily.
However, after the Prayer he has to do wudu’ for the next Prayer if something comes out after the first Prayer, and he has to clean his clothes for the next Prayer.
He should try to wear a pad to absorb what comes out so that it does not contaminate his clothes. He should change or remove the pad before each Prayer.
He can pray in congregation but he should not lead the Prayers when he is in this state because his purity is incomplete. He should also try to get treatment for this.
Allah Almighty knows best.
Excerpted, with slight modifications, from: www.islamqa.info