If during the cataract operation (eye surgery) blood comes out of the pupil but it remains inside of the eye and does not reach the eyelashes or the outside corner of the eye, the wudhu will not break.

A large body of water (ماء كثير) or 10 x 10 dhira’ is defined as one whose surface area (the product of the length and width) is 100 dhira’ which is equivalent to 225 square feet.

Sometimes, insecticide powder is added to the water to kill the germs. Even though it causes a change in the colour, smell and taste, the liquidity and fluidity of the water remains. To perform wudhu with this type of water is permissible.

If only one of the three qualities of Dettol (colour, smell, taste) becomes apparent in the water [after adding it to the water], then it will be correct to perform wudhu with it.

Zamzam water is blessed water.  It is a Shari responsibility to respect the water and consider its etiquettes.  Therefore, it is makrooh (reprehensible) for a person who does not have wudhu to perform wudhu with it, provided that there is alternative water available,

Urine is impure. If it is filtered, it would still remain impure because by filtering, it simply removes the foul odor. 

If when using an injection to insert (any medicine or) glucose (into the body), a lot of blood (i.e. that amount of blood which would have been able to flow on its own) comes back into the needle,

If the blood removed by the syringe was not enough to flow then the wudhu will not break, but if the blood was in such a large amount that it would have flowed from its spot then the wudhu will break.

Endoscopy is the insertion of a thin tube into the body through the back passage which is used to examine the internal organs. By inserting this, the wudhu will break.

By applying Khidhab (Mehndi) to the hair, no coat (body) [of the dye] remains on the hair, rather only the color remains. Therefore, the presence of such color, does not prevent [the validity of] wudhu and ghusl.