A gallbladder hypodense shadow is a lesion of lower density than the gallbladder parenchyma found inside the gallbladder on CT, which may indicate gallbladder polyps, gallbladder stones, gallbladder cysts, and malignant tumors of the gallbladder. 1. Gallbladder polyp. When ultrasound is performed, gallbladder polyps often do not change position with changes in body position. 2. Gallbladder stones. During ultrasound examination, deep shadows can be observed on the back of gallbladder stones, and their position changes with body position. 3. Gallbladder cyst. Gallbladder cysts are often regular round or round-like, with clear boundaries. 4. Malignant tumor of gallbladder. Low-density shadow of the gallbladder may also indicate malignant tumor located in the gallbladder. It is recommended to consult a doctor after diagnosis of gallbladder hypodensity shadow, and complete relevant examinations under the guidance of a professional physician to clarify the type of lesion, and then carry out appropriate diagnosis and treatment.