Pulmonary segregation is a rare congenital malformation of the lung, which is an embryonic developmental defect based on vascular anomalies. Signs lack specificity and are easily misdiagnosed. The pathogenesis of this disease is still inconclusive, but most support the theory of traction, that is, in the early embryonic stage, there are many visceral capillaries connected to the dorsal aorta around the prointestine and lung buds, and when the lung tissue is separated, these connected vessels are gradually declined and absorbed. In the early embryonic stage, when the lung tissue is separated from the primary intestine, the pulmonary buds are located in the pleura, forming intrafollicular pulmonary segregation. The pathology of pulmonary segregation is characterized by the fact that the diseased lung tissue receives blood from the arterial system of the body circulation, and due to the traffic with the body circulation, the arterial pressure increases significantly, causing cystic changes in the lung tissue. Clinical features Pulmonary segregation mostly develops after 20 years of age, more males than females, more left-sided than right-sided, 97.75% of intralobular forms are located in the lower lung, and most are located in the inner basal segment! The incidence of extralobar pattern is 1/3~1/6 of intralobar pattern, and 77.4% of the lesions are located between the lower lobe and the diaphragm. The clinical manifestations of the disease lack specificity, mainly presenting with respiratory symptoms such as cough, coughing up pus, chest pain, fever, etc. The severity of symptoms is related to the size of the intrapulmonary cystic cavity and whether it is co-infected, and a few cases have recurrent episodes of dyspnea, cyanosis and hemoptysis. The disease has a high rate of misdiagnosis and is easily confused with some common respiratory diseases such as pulmonary cyst, bronchiectasis, inflammatory pseudotumor, and lung cancer. In extralobar pulmonary isolation disease, the lung tissue does not communicate with the bronchi of the normal lung lobes, and these patients may not have any symptoms and are often detected during health checkups. Thus, when inflammation of the lower lobe of the lung occurs repeatedly, the possibility of intralobar type pulmonary isolation should be considered. Examination methods X-ray chest radiography is the most basic method to diagnose pulmonary isolation disease, which often shows a mass or infiltrative sign in the lower lobe, mostly located in the posterior or medial basal segment, characterized by a dynamic intra-pulmonary shadow that may shrink after treatment but does not disappear for a long time. The chest line presentation of pulmonary isolation disease is not specific, especially when co-infected. The most important aspect of the diagnosis of pulmonary isolation is the presence of abnormal blood supplying arteries from the body circulation to the intrapulmonary lesion, and the traditional gold standard for diagnosis is the use of an invasive test, angiography, which is not often used in clinical practice because of its invasive nature. Because CT is non-invasive, it has become the main diagnostic tool for this disease. The most diagnostic sign is a lesion with a striated stalk connected to the thoracic aorta, spinal column, or inferior pulmonary veins, and the overall morphology of the lesion shows a wedge-shaped shadow with the tip pointing to the paraspinal column. However, the detection rate of abnormal vessels by CT is not high. With the continuous development of medical imaging technology, especially the popularization and upgrading of multi-row spiral CT, the vascular imaging after spiral CT enhancement scan can visually display the whole picture of abnormal vessels, and provide more accurate and intuitive information on the origin, course and branches of abnormal blood supply arteries and returning veins. MRI is also considered to be the main diagnostic method for pulmonary isolation because of its ability to visualize isolated pulmonary circulation arteries without the need for contrast. Once isolated lung disease is diagnosed, even if the patient does not have any clinical symptoms, aggressive surgical treatment should be performed with the aim of removing the infected lesion, eliminating the left-to-right shunt in the isolated lung, and preventing distant infection or incidental carcinoma at the lesion site. Usually, lobectomy is performed for intralobar lesions and resection of lung segments or isolated lung lesions is performed for extralobar lesions. Pre-operative pulmonary infections should be controlled before surgery, and the source and number of blood supply arteries should be clarified to prevent bleeding due to inadvertent injury to large vessels. Due to the high rate of misdiagnosis of pulmonary isolation, a significant number of cases are only discovered intraoperatively. Therefore, for lesions in the lower lung near the diaphragmatic surface and mediastinum, especially if the lung surface is pink and congested, it is important to be alert to the possibility of the existence of this disease intraoperatively and pay attention to explore for any malformed vessels to prevent accidents.