Just wanted to share something that worked for my chihuahua, who had been suffering from "gurgle belly" and vomiting a yellowish, foamy substance . My husband searched online and found a site that suggested changing her diet to a food that lists beef as the first ingredient instead of grains or chicken. Since she started this new diet (1/2 - 3/4 cup of food per day), she rarely vomits and her coat looks much better. We're so relieved!!
(You may want to consult your vet first if you're thinking of trying this as it may not be the answer for your little one.)