Hi, sorry to hear about your frog. Thanks for the picture. This sounds a bit crazy, but try this out:

Move the affected frog to a hospital tank. Now make him a sugar-water bath, using 1/2 teaspoon sugar to 1/2 cup room temperature spring water. Mix it well. Place the frog in the bath. Leave him undisturbed for a couple of hours. Then look to see whether this has worked.
If you suspect it is protozoans, try Pedialite instead. This is the human child's version of electrolytes, or salts. Make a bath in the same way. Follow the same procedure as above. If this does not cause his anal walls to contract and suck in the intestines, the frog will need to see a vet asap.

I found this on a frog first aid site. Let me know how it works