My question is should it be a concern that my dog hasn't had a stool since she got hit by a car four days ago. She has broken left femur, fractured pelvis and dislocated left hip. She had surgery on the hip to put into place. Is urinating. Not eating. Drinking. On pain meds and antibiotics. She was given two enemas today to try to get things moving.

All the drugs to knock her out and pain meds are slowing down her system. Giver her some time

Since she is under a vets care, keep in touch with the vet. Nobody here can give you a better answer.

Just an observation, you said in the post that she is not eating.. this would more than likely be on cause for her inability to eliminate.. as there is nothing to eliminate...

My question is should it be a concern that my dog hasn't had a stool since she got hit by a car four days ago. She has broken left femur, fractured pelvis and dislocated left hip. She had surgery on the hip to put into place. Is urinating. Not eating. Drinking. On pain meds and antibiotics. She was given two enemas today to try to get things moving.
All of the above answers is correct. The pain medicines can cause constipation. Keep your vet advised of any bowel movements or lack of. Also advise your vet that your dog is not eating. You may need to get the dog some nutrition via a feeding tube or IV if it continues to not eat.