[Congenital unilateral absence of pulmonary artery: a case report].

A young male patient with prior patent ductus arteriosus (PDA) surgery presented with hemoptysis caused by previously undiagnosed congenital unilateral absence of the right pulmonary artery (UAPA).

• The patient's chief complaint was hemoptysis.
• The patient had a prior surgical history of patent ductus arteriosus (PDA) repair.
• UAPA had not been diagnosed at the time of PDA surgery, indicating it can remain clinically hidden.
• The case illustrates that UAPA may coexist with other congenital heart conditions and go undetected until a triggering event.

Computed tomography pulmonary angiography (CTPA) confirmed complete absence of the right pulmonary artery with an independent anomalous vessel originating from the aortic arch supplying the right lung.

• CTPA was the definitive imaging modality used to confirm the diagnosis.
• The right pulmonary artery was completely absent.
• Blood supply to the right lung was provided by an independent abnormal vessel originating from the aortic arch, as well as bronchial arteries.
• This represents a rare form of UAPA with anomalous aortic arch collateral blood supply.

Hemodynamic changes following PDA surgery may accelerate pathological processes in systemic collateral vessels and thereby induce hemoptysis in patients with coexisting UAPA.

• Prior to PDA closure, the ductus arteriosus may have contributed partial blood flow to the affected lung, partially compensating for the absent pulmonary artery.
• After PDA surgical repair, altered hemodynamics may have increased the burden on systemic collateral vessels supplying the right lung.
• This accelerated pathological remodeling of collateral vessels is proposed as the mechanism triggering hemoptysis.
• The paper describes this as 'the potential mechanism by which the hemodynamic changes after PDA surgery may accelerate the pathological process of systemic collateral vessels.'

Clinicians should broaden differential diagnosis to include pulmonary vascular malformations such as UAPA in patients with a history of congenital heart disease surgery who develop hemoptysis.

• UAPA is described as a rare congenital vascular malformation with diverse clinical manifestations and often challenging diagnosis.
• The case emphasizes that pulmonary vascular malformations can be masked or undetected at the time of initial congenital heart disease surgery.
• Hemoptysis in a patient with prior PDA surgery should prompt consideration of underlying vascular anomalies.
• The authors state clinicians should 'actively broaden the differential diagnosis thinking and consider the possibility of previously hidden pulmonary vascular malformations.'