An irregular nodular focus seen in the hilar of the left lung is a description of a parahilar lesion on imaging, and common causes include lung cancer, inflammation, vascular malformation, and pulmonary nodular disease. 1. Lung cancer: the nodular foci are usually irregular in shape, lobulated, and some of them even have burrs on the edges, which are not clearly demarcated from the surrounding tissues. 2. Inflammation: mostly caused by infection, such as tuberculosis foci, which are round nodular foci with high density and clearly demarcated from the surrounding tissues. 3. Vascular malformation: it belongs to congenital developmental abnormality, and the tortuous and dilated malformed blood vessels will be changed accordingly. 4. Pulmonary nodular disease: it can be manifested as multiple enlarged lymph nodes next to the pulmonary hilum and reticular nodular shadows in the lungs. Irregular nodular foci next to the left lung hilar can also be seen in other diseases, and it is recommended that the patient seek medical treatment in time to avoid delaying the condition.