Felt like another rectal prolapse in the making. I have meanwhile written about this scary phenomenon in my Chaos Node and got a possibly useful reply from another sufferer. Evidently it is familial, and never heals, though it does nor progress in all victims either. Anyway, there was nothing I could do about it at work. By the time I came home, my heart was already beating like I was mowing the lawn (a side effect from the constant strain, I assume) and I was weak and thirsty. Luckily the colon was only moderately distended and after adding water, I was able to empty over the course of some minutes. It seems to have snapped back to normal or near normal shape now. I suppose I could return to work now, but there often follows a bout of diarrhea afterwards (though I am not sure if that is cause or effect). Also, it is already afternoon here in Norway, so I'll take the rest of the day off and hope I can get the work done tomorrow. (Another batch of the usual Monday files, not really time-critical. They often come on Tuesday anyway.) The rest of the gang were at work so they should be able to handle any acute requests at least as well as I. It doesn't seem worth the risk of severe public humiliation.
I suppose my boss could read this if "I was sick" is not good enough. I don't recommend it though.
On the up side, these events make it easier to consider the brevity of life, the certainty of death and the duration of the hereafter.