Sadly, goldfish dropsy isn't a smart name for an unusual breed of fish: It is in fact a condition that affects fresh-water goldfish that can speedily lead to death of the infected fish and even others around it. It is commonly relatively simple to detect, as the fish pets will have a really bloated stomach, stained scales and their scales will also start to thrust outward, instead of stay close to their skin.
Preventing goldfish dropsy is a lot simpler than curing it. The most notable cause is from bacteria that is introduced either by the water you use, infected food, or basically water that hasn't been cleaned/filtered appropriately. Having a good aquarium filtration system in with your fish is perhaps the most effective way for you to avoid contamination from happening in the first place. Prevention will function in nearly 80% of entire fish: Prevention isn't usually possible, since goldfish dropsy can also be caused through kidney, heart or liver ailment in the fish which may be brought on by normal, or unnatural causes.
There are goldfish dropsy water remedies that can be included that can or may not help based on the fish's condition and how far the dropsy has progressed. Aside from any external medicines you provide them; separate the infected fish from others immediately. For the most part it would seem that dropsy isn't infectious, but the added stress of other fish pushing it around and nibbling at it may push the fish over the edge and trigger death.
Let Nature Take its Course
Eventually, it will be up to nature and the fish pets as to whether it will endure the dropsy or not. Let nature take its course: Don't handle the affected patient and let them rest. Obviously you will undoubtedly want to monitor them, but refrain from poking them or scaring them at all costs.