My 1 year old has trouble ping bowel movements.?

Hours before a movement pes there will be a little staining, like very light loose stools. When she finally completes a bowel movement it is accompanied by very small sand like pebbles. A doctor will be able to evaluate her in the near future. Until then I worry about her and would really appreciate any wisdom on this topic. Let me know if you would like any additional information. My 2 year old is exceptionally healthy on the same diet, which is a very mindful diet. I am worried the problem may rest beyond the dietary realm... Thank you.