Is the clear, shiny discharge that comes out after Istinja’ from urine and Wadiyy impure? Does one have to purify oneself from it? What is its cause, and how should it be dealt with, Islamically and hygienically?

What the questioner sees may be residual water from istinja' (washing after relieving oneself), or it may be from the normal moisture known as vaginal discharge. This discharge is considered pure (tahir) according to the most preponderant opinion, and it does not necessitate istinja', but it does nullify wudu' (ablution). Therefore, it is not necessary to wipe oneself from these secretions, nor to perform istinja' due to their emission, nor to insert anything to prevent their emission. Rather, she should not perform wudu' unless she is certain that their emission has ceased. If she doubts their emission, the default is that they have not occurred. If she doubts the nature of what has exited, she has a choice. As for the health aspect, she should refer to the consultations section.