What kind of complications might happen from a cta?

Allergy. The main risk is concern for an allergic reaction to the contrast dye. Damage to the kidney is also a big concern. The good thing is that the kidney can usually recover from this on its own with IV fluids and careful observation.
Few. Mainly contrast or dye allergic reaction, renal damage from the dye, and injection of the dye inadvertently under the skin. Go to accredited scanner to avoid risk of too many xrays during scan.