He is suffering from some secretions: how should he do wudoo’ and pray?
Question

I am suffering from a medical condition that causes some secretions from my anus. Do I have to change my underwear before doing wudoo’ and praying?
Praise be to Allah.What is required of the worshipper is to purify his garment from impurities when he wants to pray, to the best of his ability, because Allah, may He be exalted, says (interpretation of the meaning): {And your clothing purify} [al-Muddaththir 74:4].
If you are able to allocate clean clothes for praying in, then take them off after you have prayed, lest they become contaminated with impurity, that would be a good idea.
If you cannot do that, then put some kind of cloth, tissue or other kind of protection [such as a pad or diaper] in the place that is affected by the impurity, which will prevent the impurity spreading onto your clothes or body, then remove it at the time of prayer, and wash the impurity from your body.
If it is too difficult for you to do that for every prayer, then you can put prayers together, as it may appear. So you could delay Zuhr until the end of its time and pray ‘Asr the beginning of its time, then do something similar for Maghrib and ‘Isha’. In this way you only have to change your clothes, or the diaper that prevents the impurity from spreading, three times every day.
If you are not able to do that either, then there is nothing wrong with praying as you are, because Allah, may He be exalted, says (interpretation of the meaning): {Allah does not charge a soul except [with that within] its capacity} [al-Baqarah 2:286].
Shaykh Ibn Baaz (may Allah have mercy on him) said: In the case of one who is affected by urinary incontinence who has not recovered after being treated for it, he should do wudoo’ for each prayer after the time for it begins, and wash off anything that has got onto his body, and he should allocate a clean garment for prayer, if that is not too difficult for him to do. Otherwise, he is pardoned because Allah, may He be exalted, says (interpretation of the meaning): {and [Allah] has not placed upon you in the religion any difficulty} [al-Hajj 22:78] and {Allah intends for you ease and does not intend for you hardship} [al-Baqarah 2:185]. And the Prophet (blessings and peace of Allah be upon him) said: “If I instruct you to do something, then do as much of it as you can.” And he should take precautions to prevent the urine spreading on his garment or body or the place where he prays.  "Fataawa Islamiyyah (1/192)"
For more information on the rulings on one whose wudoo’ is constantly invalidated, please see the answer to question no. 39494 .
And Allah knows best.