Double Mastectomy with Tissue Expanders. Left Side is Much Bigger - Normal?

Another possibility is that the tissue expander on the one side might have rotated out of it's anatomical position making the breast appear larger compared to the other side. If the filling valves are on very different areas on both breasts it would support this potential problem. Exploration might be required.

The size discrepancy can be reconciled at the time of placement of your permanent implants.  You have had a CT scan which I assume did not show any abnormality.  Continue to follow up with your surgeon.

Even with a scan you may still have fluid. I think re exploration is the best choice. Discuss this idea with your plastic surgeon. Uneven expanders can occur but there should be a medical reason. Best of Luck

I assume you have the same volume of fluid injected into each tissue expander. One side can always look a bit bigger because of the overlying muscle, underlying skeletal structure, thickness of the soft tissue envelope.  This can be adjusted when the permanent implants are placed.