A right to left Patent Ductus Arteriosus (Reversed PDA or rPDA) is a congenital defect where the ductus arteriosus (fetal vascular connection) remains present after birth.  

The pulmonary pressures rise dramatically due to a problem within the lungs (Eisenmenger’s Physiology), causing blood to flow from the main pulmonary artery into the descending aorta.  

This high concentration of deoxygenated blood causes a high degree of deoxygenated blood to flow to the back half of the body, particularly the kidneys.  

This is seen clinically as differential cyanosis (blue/purple caudal membranes, pink cranial membranes).  A rPDA results in severe elevations of the hematocrit (PCV or HCT) as the kidneys respond to the deoxygenated blood by signaling for more red blood cell production.  

Affected patients will typically become neurologic (seizures, altered mentation, weakness, collapse, inappetance, or trembling) as the hematocrit rises.  

These patients are also at risk for sudden death due to arrhythmias, neurologic conditions (embolic events or seizures), or potentially right-sided congestive heart failure.

There is no cure for this condition.  Therapy is directed towards lowering the pulmonary pressures, thus reducing the degree of shunting and therapeutic phlebotomy (blood draws) as necessary to maintain the hematocrit around 60-65%.  

The prognosis is typically poor; however, some patients will live for many years with optimal medical management.