Correct!
3. Left lung aplasia
Pulmonary underdevelopment (Figure 4) has been classified into three broad categories: pulmonary agenesis (Figure 4A), pulmonary aplasia (Figure 4B and C), and pulmonary hypoplasia (Figure 4F and G).
Figure 4. Pulmonary underdevelopment. A: left lung agenesis. Note extensive left lung volume loss with complete shift of cardiomediastinal structures into the left thorax. At CT (not shown), no left pulmonary artery or veins, left mainstem bronchus, or lung tissue was present. B and C: right lung aplasia. Note extensive right lung volume loss at chest radiography. Consolidation in the left base represented pneumonia, which brought the patient to clinical attention. Right lung tissue and a right pulmonary artery are absent, but note the presence of a right mainstem bronchus (white arrowhead, C), which distinguishes pulmonary agenesis from pulmonary aplasia. D and E: Right pulmonary hypoplasia. Note presence of a right mainstem bronchus (black double arrowhead, D) and a small amount of rudimentary pulmonary tissue (black arrowhead, E) and a severely hypoplastic right pulmonary artery (white arrowhead, E) supplying the rudimentary lung tissue. F and G: Interruption of the left pulmonary artery. Note volume loss on the affected left side with absence of the proximal left pulmonary artery. Although the left thorax is hypoplastic, left lung is present and left-sided bronchi are present. Note presence of systemic arterial supply derived from the bronchial and intercostal arterial circulations (arrow, G) that eventually reconstitutes more distal left pulmonary arterial branches. The aortic arch is right-sided and often interruption of the pulmonary artery occurs on the side opposite of the aortic arch.
Pulmonary agenesis (Figure 4A) represents complete absence of the lung parenchyma, bronchus, and pulmonary vasculature, whereas the term pulmonary aplasia (Figure 4B and C) refers to complete absence of the lung parenchyma and pulmonary vasculature, but with the presence of a blind-ending, rudimentary bronchus, which fits the CT appearance of this patient. Pulmonary hypoplasia (Figure 4D and E) is present when a bronchus and rudimentary lung are seen and pulmonary arteries are also present, but are decreased in size and number. Interruption of the pulmonary artery (Figure 4F and G) is characterized by volume loss and abrupt truncation of the proximal pulmonary artery on the affected side, with the more distal pulmonary arteries on the affected side reconstituted by systemic vessels, often derived from the bronchial and intercostal circulations. Venous drainage on the affected side is typically normal, and lung, albeit hypoplastic, is present.
Diagnosis: Left lung aplasia presenting due to incidental development of right lower lobe bronchopneumonia
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