Protein-losing enteropathy in a child with hypoplastic left heart syndrome after Fontan palliation: a case report.

Protein-losing enteropathy (PLE) is a rare but serious complication of the Fontan procedure in patients with single-ventricle physiology. It results from excessive loss of plasma proteins into the gastrointestinal tract, leading to hypoalbuminemia, edema, and ascites. We report the case of a 10-year-old girl with hypoplastic left heart syndrome who underwent staged surgical palliation including the Norwood procedure, bidirectional Glenn shunt, and extracardiac Fontan completion. She presented with progressive abdominal distension, peripheral edema, and severe hypoalbuminemia (albumin 2.3 g/dl). Echocardiography and cardiac catheterization demonstrated a patent Fontan circuit with normal pulmonary artery pressures and no significant obstruction, although the inferior vena cava pressure was mildly elevated at approximately 16 mmHg. The patient was managed with intravenous albumin replacement, diuretics, anticoagulation, sildenafil, and oral budesonide. This case highlights the diagnostic challenges of PLE and emphasizes the importance of early recognition and multidisciplinary management, even in the absence of significant Fontan circuit obstruction, as elevated systemic venous pressure and lymphatic dysfunction may both contribute to disease development. Key Clinical Message: Protein-losing enteropathy is a rare but potentially life-threatening complication of Fontan circulation. It should be suspected in patients with a history of Fontan palliation who present with unexplained hypoalbuminemia, edema, or ascites, even when no significant Fontan circuit obstruction is identified, as elevated systemic venous pressure and lymphatic abnormalities may contribute to disease development. Early recognition and multidisciplinary management are essential to improve clinical outcomes and guide further evaluation of underlying lymphatic abnormalities.