I had nuclear med scan for gallbladder sludge yesterday. Why are they waiting to compare results from findings on first catscan I took 2 weeks ago?

Not sure. Most likely want to compare images and the radiologic impressions to make sure they " match" , i.e., nothing is left out of the report .
Proper diagnosis. When evaluating imaging studies, it is always helpful to compare all other imaging modalities already performed, ct, mri, ultrasound etc. There may be findings that would help diagnose more accurately your condition. It is the right thing to do. Good luck!
Not sure. Don't know findings on ct scan. Ct is not very accurate in detecting sludge or gall stones. Some biliary duct dilatation is seen on ct scan and ultrasound, sometimes secondary to duct obstruction. Hida scan can not only demonstrate gb disease but can suggest bile duct obstruction. I would ask your doctor?