Well looking at the photo, I do not believe it to be fake, as much as I do an urban legend.
The only thing in my mind that makes this an urban legend is the fact that no one knows the origin.
However, I think we're mistakenly taking the story behind it as true, thus it would become less and less possible.
However, that could easily be a child. Now if that were the case, I believe it would be fully possible.
The thing to keep in mind is that the buldge in the snake is definately not fake. However, with the snake intact, we don't know what the buldge is.
The seperate picture, after the snake had been cut open, depicts what we take for an adult, since the caption say so. However, if you consider that the average Anaconda is no bigger around than the size of an average can of coffee, and while their flesh and skin is remarkably elastic, the buldge in proportion to the diameter of the snake, does not tell me that it's an adult person, if it is a person that does the create the buldge.
It would almost have to be child, and as I said, if that were the case, it would make the entire thing extremely possible. A small child would be near the size of a small pig, small deer, etc (excuse the the apparent lack of sympathy, this is simply for comparison sake), which Anacondas, while with some struggle, have been known to swollow.
Now, while urban legend sites that cover this story say that we would have heard this on the news....this is not accurate. How many people in the United States are murdered every day, that we hear nothing about?
If this were a small village, etc, there is a good chance we would know nothing about it. In fact there are villages in South America, and all over the world, that no one has heard of, let alone been covered by the likes of CNN, etc.