None. Both tests the same: gallbladder function, but use different trace material.
Injected radioactive. Medical tracers (radiopharmaceuticals) are different. Hida is an earlier agent, with pipida as a newer agent. Many imaging centers now use disofenin. All work the same way, but the newer agents are more effective in patients with poor liver function. Most places still call the examination a hida scan, even though hida is not being used.
Not much. 99tc hepato iminodiacetic acid (hida) is rarely used currently, as 99tc paraisopropyl iminodiacetic acid (pipida), 99tc diisopropylacetanilido iminodiacetic acid (disida/disofenin) or 99tc bromo-2, 4, 6-trimethylacetanilido iminodiaceticacid (brida/mebrofenin) have replaced it, but the term hida remains. All agents are extracted from blood stream showing liver, gb, bile ducts, and bowel.