Does a low functioning gallbladder get better with diet? hida scan showed only 17% functioning what's the chances of rupturing or gettinh gangreen?

Function will likely: Not get better, but what really matters are your symptoms. If your gb does not empty normally, the chances of getting gallstones increase (because of bile stagnation or stasis). If a gallstone gets stuck in the biliary tree, that can lead to acute biliary colic and/or cholecystitis, which will have to be treated, sometimes emergently.

Scan: Hida scan is is only a means of evaluating the gallbladder function at that time & the results are highly variable and may be very different if checked on a different day. It us not a highly reliable test. Mainly depends on your symptoms. Pain? Pain during the scan? No, your gallbladder is functioning & will not rupture or get gangrene. Healthy duet is always good but likely not change gb function.

unlikely: The good thing with seeing the gallbladder(you can't calculate an ejection fraction unless the gallbladder filled first) is that it is very good with predicting that there is not acute cholecystitis...So gangrene and rupture very unlikely at that time. However an ejection fraction of 17%, is low. This is most commonly related to a chronic disease, and indicates poor function.