There are many possible reasons of spots on your gallbladder. Previously, it was very difficult to diagnose these problems but with the advancement in the imaging techniques like MRI, CT scan and ultrasound, the diagnosis has become easy with least chances of error. These spots on the gallbladder can be due to cholesterol polyps, inflammatory polyps, adenomas, hyperplastic pre-malignant lesion, lipomas, hemangiomas, leiomyomas, and adenocarcinoma. Your doctor can have differential diagnosis, so, visit a doctor.