Patent ductus arteriosus (PDA) is an open communication between the upper descending thoracic aorta and the origin of the left pulmonary artery. It is the result of persistent patency of the foetal arterial duct and has an incidence of up to 1 in 2000 of the population born at term. At birth, the arterial duct is patent but spontaneous closure occurs during the first 24 h of life with contraction of the smooth muscle in the media. This functional closure is assisted by the approximation of the intimal cushions which protrude into the lumen. Complete closure usually occurs by the age of 3 weeks as a result of diffuse fibrous proliferation of the intima. But in 10%, this process may be delayed by several weeks. Closure usually begins at the pulmonary artery end and may remain incomplete adjacent to the aorta leaving an aortic ampulla from which the ductal ligament arises.¹ There is some variation in the morphology of a patent ductus, which may be long or at the other extreme, characterised by a window between the descending aorta and proximal left pulmonary artery. When there is persistent patency of the arterial duct, it histologically differs from the normal duct and from the adjoining great arteries.¹ It may therefore be considered a congenital abnormality of the wall although, currently, at least 15% of children presenting with a small to moderate arterial duct …