The feeling of diarrhea coming in waves?

Factual Questions
1

When I get diarrhea and I have to hold it until I get to a bathroom, the feeling of it pressing against the inside of my anus comes in waves.

When it gets to that point, I’ll have a severe and immediate need to shit, bordering on hysterical, and its all I can do to clench my butt like a vice to prevent the brown river from flowing. This feeling lasts usually anywhere from 30 seconds to a minute

However, after that wave passes, I can usually go a couple of minutes feeling just a little bloated but without the immediate need to spray out my hershey highway on anyone within arm’s length.

Why does the need to go come in waves that crash unto the gates then dissipates? Nothing’s flowing back and forth in there, I’m not sloshing around, I don’t feel like liquid is going up and down my intestines. Why the tidal wave of pain and numbness?

2

I think it’s the muscles themselves tightening and loosening in waves.

The same effect can be felt when having a perfectly ordinary bowel movement. Some stuff falls out…then you wait a bit…and then more stuff moves down and is ready to fall out. There seems to be a sort of natural 20 - 30 second periodicity to the peristaltic contractions.

(When playing a Fantasy Football kind of game, with made-up players, one of my team was “Perry Stalsis.”)

3

See peristalsis.

4

I have the same problem. But it is more serious. I take Tamsulosin. It relaxes the sphincter muscle. When I gotta go, I have 30 seconds to find a depository. Fortunately, it happens at a predetermined time. So, I don’t leave the house until it happens.