I am not in medical school so I will defer to you, I never ment to imply they where common in daily practice, nor that the midevil blood letting, or new age leaches where medicle, but I have found a few NIH papers on it... and remember reading about how its used in like didget reattachment because they prevent blood clots

here is one paper I found https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5741396/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7288891/