I also had my gallbladder out, which left me unable to eat a meal without suffering extreme diarrhea about 20 minutes later. I found a good gastroenterologist and described my symptoms, and he recognized them immediately. Surprisingly common, he said. He said that the gallbladder served as a reservoir of bile acids produced by the liver, holding them in reserve until needed to help digest fats. A "bladder" for "gall". Unfortunately, bile acids can be irritating to the intestines, so if the gall bladder isn't available to catch it, it will drip into the intestines when there is no fat for it to work on, causing a chronic bowel irritation in many people that can result in diarrhea.
After many gallbladder surgeries, the tubes carrying the bile from the liver to the GI tract will stretch a bit and recreate a bit of the reservoir function of the "nearly useless" gallbladder, but this doesn't happen in everyone. I was not so lucky.
Without hesitation, he prescribed Cholestyramine powder (I get a generic version), which is a "bile acid sequestrant", which is a resin that encapsulates bile in the intestines. It changed my life in one dose. Problem instantly vanished. I was once again able to both leave the house AND eat on the same day. Just one problem: it was not a cure. It just sequestered some of the bile acid that my missing gallbladder used to sequester. If I missed even a single day, the diarrhea would return with a vengeance the following day unless I fasted all day.
Like many other people, I'm lucky to have this $150/month medicine, which gave me my life back, but I'll have to take it every day for the rest of my life, never missing a day, because I need it to compensate for the lost gallbladder--you know, the one that medical science has proven to be nearly useless.