What will it mean that our granddaughter's urine test showed orotic acid?

Extra orotic acid. In 'ornithine transcarbamoylase deficiency', a disorder of the urea cycle, extra orotic acid is made. This leads to increased urinary orotic acid excretion, because the orotic acid is not being properly utilized and must be eliminated. The doctor must be suspecting this or they would not have tested so check with the doctor on what all that means.