Not counting anything with actual cadavers, learning about bed sores was definitely the roughest.
Text hidden for medical grossness of both the ethical and corporeal variety
Summary
So bed sores come from extended pressure on one part of the body, usually for patients who spend a lot of time in bed. They're most common on elderly people with fragile skin, and, once they develop, can be fatal. Like... 75% mortality rate fatal. But here's what makes them horrific
First, they are some of the more upsetting injuries to see. I won't post pictures, but plenty of people shared loved ones with wound inches across. They look like somebody look an icecream scoop to their body and then let it rot.
Second, they're completely preventable by just turning patients regularly, yet they kill 60,000 people in the US alone. At best, they're the result of a fragile body and an understaffed medical group. At worst, they can be considered horrific neglect.
Just the idea of being unable to move myself and feeling my bodypainfully rotting away, and then knowing this experience is actually a common way to die is... whoof. Also, it's very hard to research them without seeing a lot of photos. I can deal with fictional gore, but real gore gets me.