A 21-year-old white woman, born with a univentricular heart, had undergone staged procedures before Fontan correction. She then began to develop edema, protein-losing enteropathy, and ascites refractory to diuretic therapy. Cardiac angiography showed a patent right Blalock-Taussig shunt, with turbulent cavopulmonary circulation. After undergoing an unsuccessful attempt at coil embolization she then underwent shunt ligation, with resolution of symptoms and normalization of protein levels. This report draws attention to the importance of cavopulmonary laminar flow to prevent the development of protein-losing enteropathy.