Brief Answer: Filling of air spaces in lung with fluid, cells. Detailed Answer: Hello, I have gone through your query and understand your concern. I think you are mentioning about Lung or Pulmonary infiltration. Infiltration in lung is filling of air spaces in lung with fluid , inflammatory exudates, or cells (malignant cells, red cells or haemorrhage) that fill a region of lung and increase the visual impression of increased soft tissue density in X-ray and other radiological findings. Regarding the lobes. The right lung has 3 lobes: Right upper lobe, middle and lower lobe. The left lung has 2 lobes: Left upper lobe and lower lobe. You have infiltration in either Left or Right or both. There are many causes for Pulmonary or lung infiltration. Some common causes are Atlectasis, Tuberculosis, Pneumonia, Pulmonary edema etc. However these finding in X-ray or CT is to co-related with clinical findings by examination and history to identify the exact cause and then only proper further investigation and treatment should be started. Hope this helps. Please write back for further queries. Wishing you good health.

---