I found this thread (and others like it) the other day when I was trying to figure out a pain I had in my left side, right under my lower rib.
A few months ago, I was diagnosed with a urinary tract infection that had no symptoms except that my urine smelled funny (no pain). I took antibiotics and it seemed to go away, but I was wondering, since the pain seemed like it could be in the kidney area.
One site that talked about kidney infections also mentioned kidney stones. I figured it couldn't hurt, so I followed the instructions: I took some cranberry concentrate pills and drank like 7 tall glasses of water.
After that, my urine was still yellow. Then, I felt the pain kind of go "ping!" like something moved. Then it went away, but I felt a cramping feeling down my groin.
The next time I went to the bathroom, my urine was clear and I saw what looked like a grain of sand fall to the bottom of the toilet. And no more pain!
Still not sure if it caused or was caused by the UTI I had earlier... I plan to get another urine test... but I wanted to post this in case it applies to you.
To the poster who said it comes after you drink beer or work out a lot - that's one of the main symptoms! Dehydration is a big cause, along with an OD of Vitamin D, UTIs and other things. So don't assume it's your spleen or something horribly wrong with your colon... it could just be a small kidney stone.