[The image is the key: unilateral absence of a branch of the pulmonary artery].

Unlabelled: Unilateral absence of pulmonary artery (UAPA) is a rare and underdiagnosed entity. Due to its varied clinical expression, especially respiratory and most frequently associated with congenital heart disease, it can also present in isolation and remain asymptomatic for a long time. There is no consensus on its treatment, which is generally reserved for the presence of complications, mainly pulmonary hypertension, hemoptysis, or recurrent respiratory infections.

Objective: To describe two cases of UAPA identified early in life, and the usefulness of routine imaging tests for its diagnosis.

Clinical Cases: We present two clinical cases of asymptomatic children referred for pediatric cardiological assessment. The first one was 1 month old, with a prenatal diagnosis of right aortic arch, that was referred to rule out associated anomalies. An echocardiographic evaluation confirmed left isolated UAPA, sustained by plain radiography. CT angiography confirmed UAPA and left lung hypoplasia. Only clinical follow-up was determined. The second case is a 2-week-old neonate who was referred due to a systolic murmur. Right pulmonary artery agenesis was diagnosed by echocardiography with no other associated defects and was confirmed by CT angiography. Plain chest radiography showed no alterations initially, however, after 1.5 months of follow-up, right lung collapse was detected so clinical follow-up was decided. Both cases were suspected by echocardiography and confirmed by CT angiography. At 1.5 years and 6 months old, respectively, they show a good evolution, with good growth, and close monitoring of their intercurrent respiratory processes.

Conclusions: UAPA can be asymptomatic when occurs in isolation and go unnoticed. Through simple imaging methods, especially echocardiography, it can be suspected and must be confirmed later by CT angiography or MRI angiography.