I was reading up on King Alfred the Great (a new miniseries on youtube about him on the BBC but also the Cornwell series of books).
A lot of "history" folks wonder why "piles" (aka Hemorrhoids) would cause such a major health concern.
Yet the diet of the Anglo Saxons, may have been low in fiber, and no one who has had hemorrhoids would think that they are not painful.
Modern doctors, who only know modern diseases, wonder if he had Crohns disease, yet if his symptoms were intermittant abdominal pain and diarrhea/constipation, one suggests a chronic amoebiasis or chronic giardia infection might be the cause.
Returning missionaries often were labled as crazy because they developed chronic irritable bowel after treatment for amoebiasis or numerous episodes of diarrhea working overseas, but who tested clear when home.
Been there, done that....had a mild case for five years, then it went away.
Yet parasites can cause low grade chronic debilitating diarrhea.
This is what killed General Braddock when he went after the French in Pittsburgh, and although the experts posit various problems, the western PA mountains were kept free of people by the iroquois, who used them as hunting grounds, so salmonella/shigella would be less likely...but Giardiasis is spread via Beavers, and there are plenty of them in that area.
So what about Alfred?
No good studies on health problems of the Anglo Saxon era, but given the high death rate at early ages of various kings, one wonders what the autopsies would show.
Alfred spent time in the marshes. Did he get Chronic tertiary malaria, or did the depopulation of the late Roman times and the cool years eliminate the disease? What about worms, and parasites?
another of the complications of constipation is a nasty problem called an anal fissure. This is caused by a break in the bowel mucosa, which causes an abcess that gradually works it's way out the skin....but unless you "deroof" the abcess and let it heal in from the bottom up (no pun intended) it comes back again and again. And when it's acting up, it hurts to poop, so you don't poop, and end up with a lot of abdominal pain.
wikipedia article here.