among the operations which lead to a partial rerouting of the systemic venous return into the pulmonary arteries, the bidirectional cavopulmonary anastomosis is frequently utilised in the staged surgical management of patients with functionally univentricular hearts. whereas some surgeons insist on closing any other source of pulmonary blood flow while performing a bidirectional cavopulmonary anastomosis, others maintain patency of either a stenosed native pulmonary outflow tract, or of a systemic-to-pulmonary arterial shunt. it remains controversial as to whether an additional source of pulmonary arterial blood flow can safely and usefully be left at the time of the bidirectional cavopulmonary anastomosis to increase systemic saturation, or whether it should be eliminated to reduce the volume load on the ventricle.