From: Rabbi Moshe Sofer
To: Rabbi Tzvi Avigdor
A woman nearing old age who had not yet established mesukekes status began consistently passing blood with her urine due to a urinary tract condition. The Chasam Sofer rules leniently, prescribing the moch dachuk examination to confirm the blood originates from a urinary wound rather than the uterus; if confirmed, she performs a hefsek taharah, counts seven clean days, and ignores blood found in urine while seated, though she is treated as tamei when dripping while standing.
Source: Shu"t Chasam Sofer YD §148