The terms proximal (from Latin proximus, meaning 'nearest') and distal (from Latin distare, meaning 'to stand away from') are used to describe parts of a feature that are close to or distant from the main mass of the body, respectively.
But, with Citrucel and/or Metamucil you can start with one teaspoon mixed in water or juice. If you have diarrhea don't use the preparation with artificial sweeteners. Use the one with sugar. I think artificial sweeteners (some of them) might cause more diarrhea.
Some people with IBS fluctuate between constipation and diarrhea, and fiber sources like psyllium supplements can both loosen constipation and bulk up diarrhea. Psyllium can be taken in capsule form or, as a powder, it can be sprinkled on oatmeal or mixed into drinks.