👉 Gallbladder is a small, sac-like organ located in the left lower abdomen. It contains bile (a yellowish liquid produced by the liver) and cholesterol. Gallstones are hard, solid stones that can cause pain or block the flow of bile from the gallbladder into the small intestine. Symptoms of gallstones include nausea, vomiting, abdominal pain, and sometimes fever. Treatment depends on the size and number of stones and how they are causing symptoms.