Why does passing a kidney stone cause a loss of appetite? is it just the associated pain? it seems my appetite is less even when i am not having renal colic?

There is no direct relationship between renal colic and poor appetite unless you take pain pill, especially narcotic contained med, for renal colic. The indirect relationship is kidney stone and kidney failure which can be a cause of poor appetite; however, only can bilateral ureteral obstruction cause kidney failure in a short time which is quite rare.

When we walk into the ER & see a patient writhing around on a stretcher, we often make a snap diagnosis of renal colic. It's no mystery why eating is the last thing on that person's mind then and for a period of time afterward.