Ive not done the marker test but I have a question. if I have colonic inertia would I be able to go so good as i am with watery d. ? I take miralax, mom , reglan and zelnorm and am able to empty out completly in the a.m after 4 trips to the toilet and I am pain free and no gas. when I was on fiber i was bloated and always incomplete and had pain. watery d. seems to be my answer but was curious if colonic inertia were the case would I still be doing so well? except for having to have the water d to go i feel wonderful, my dr. knows my deal and does blood work to make sure Im in range on everything like sodium and checks my magnesium levels from the MOM.