Hmm, I have only ever been able to identify one parasite by the presence of organs (not that I've tried that many times). I spotted something that looked kind of like a bean so I fished it out and used tweezers to open it up. I was thoroughly grossed out when I discovered that it was most definitely not a bean because it had organs.
However, I thought that most parasites were at least partially disintegrated by the time the left the body. If that's the case, couldn't some of these fragments simply be the outer skins of the parasites? If so, most of them wouldn't necessarily have organs would they?