RESUMO
Twenty five consecutive patients with multiple cannon balls in the chest X-ray were studied. The commonest causes were choriocarcinoma, multiple hydatid cysts, and breast cancer. The absence of emaciation and weight loss were important clinical clues in Hydatid disease. Lesions in hydatid were mainly in the lower zones [especially the right]. The presence of oval lesions, with flattened adjacent edges and absence of lymphadenopathy all suggested hydatid disease, while malignant deposits were mainly rounded and more in both mid and lower zones. Cavities were present in all cases of hydatids but also in some tumours. Ultrasound of the liver detected hydatid cysts in all patients with multiple lung hydatids, while ultrasound of the pelvis was helpful in choriocarcinoma. Conventional lung tomography helped to define the radiological characteristIcs of cannon balls and demonstrated lesions which were not seen by plain chest-x-ray