Dr. Greene's Answer
It is normal after a bad bout of diarrhea for the urine to be concentrated and dark while the child is getting more hydrated, but blood in the urine is something that should be checked out, as should continued dark urine once she is drinking well and no longer having loose stools.
Some of the infections that can cause diarrhea can release substances that cause blood in the urine. These need to be identified and treated appropriately.
Simple urine tests that can be done through your doctor’s office can help with the detection of blood or infection.