It sounds like it could possibly be a stuck 'stone.' If another attack happens, if possible, try mixing one level tablespoon of Epsom Salt in a very large glass of water. Drink half, wait about 20 minutes and see if it helps. If it doesn't relieve the pain, drink the other half. The Epsom Salts help relax the soft tissue and may help the 'stone' come out. Drink lots and lots of plain water as well as Epsom Salts are very dehydrating.
You may like to check into malic acid and Gold Coin Grass to help soften up the 'stones' as well. The link Vidalia gave you can give you more information on GCG. If no problems with sugar, drinking apple juice is a natural way of getting malic acid.
In the meantime, is it possible for you to do a full flush? In a full flush, the smooth tissue is relaxed BEFORE any fat or oil is introduced. When the stomach signals the liver for bile, the bile 'flushes' the 'stones' through the now relaxed (and now 'stretchier') ducts instead of being dammed up behind 'stones' stuck in tight passage ways.