Suggest Treatment For Black And Tarry Stools With Constipation In A Child

7 year old niece with severe bowel impaction, constipation and then no control what so ever of her bowels. Xray showed full of stool per ER doctor... suppositories and Miralax did not do the job.... family doctor said just constipation even tho she has stomach pain when gently pressed and stomach is very bloated... feces has extremely strong odor, is sticky, paste-like, difficult to remove from clothing, black and tarry, appearing somewhat granular and sometimes in little black hard balls...causing her much psychological stress.... unable to get into pediatric gastro doc until Feb 20th and very concerned.... could this be Celiac or Crohns or cancer or intestinal/colon blockage ...any clues to get her into the doc sooner