The cause of fistula between the gall bladder and stomach is primarily cholecystitis with formation of one or more gallstones, which by irritation cause inflammation resulting in plastic peritonitis with adhesions to the surrounding structures. The gall bladder contracts and its walls become thickened and friable. The constant pressure causes the stone to produce an ulcer which develops into a fistula. This is Nature's cure, and may also be attended by no new symptoms or the previous ones may be relieved, especially if the stones pass into the stomach and if there is no obstruction in the cystic duct and the adhesions are not numerous enough to cause trouble.
A cholocystico-gastric fistula is relatively rare, the operative cases recorded, as far as I can find, being four in number. The following table affords information as to the varieties of fistulæ resulting from cholecystitis and their frequency in recorded cases taken
SNIVELY AB. FISTULA BETWEEN THE GALL BLADDER AND THE STOMACH.. JAMA. 1903;XL(15):963–966. doi:10.1001/jama.1903.92490150015002c