Strategies to treat protein-losing enteropathy

Protein-losing enteropathy (PLE), excessive serum protein loss within the gastrointestinal tract, after Fontan operation is a poorly understood disorder. Reported to occur anywhere from weeks to years after Fontan operation, there are no identifiable risk factors for its development, and its clinical manifestations vary widely from significant morbidity and mortality to mild-to-moderate hypoproteinemia with minimal functional impairment. Treatment strategies, tailored to the severity of the disease, include symptomatic relief with diuretics and supplemental protein, attempts at halting intestinal protein leak using steroids or heparin, and alteration of cardiovascular physiology via fenestration creation, atrial pacing, or heart transplantation. A better understanding of the pathophysiology of PLE will allow the development of more effective treatment modalities. We hypothesize an abnormality of local intestinal circulation in patients with PLE that may be related to low cardiac output. Compensatory flow redistribution takes place under conditions of low cardiac output. We studied superior mesenteric artery flow using Doppler ultrasound in 40 patients after Fontan operation, 13 of whom had clinical signs of PLE, and compared them with 25 normal control patients. Diastolic velocities were lower in Fontan subjects, and the ratio of systolic-to-diastolic velocities and the resistance index were higher in Fontan patients compared with the control group. Patients with PLE after Fontan operation had higher systolic-to-diastolic velocities and resistance index than patients with Fontan and no active PLE. However, subjects with Fontan circulation but without PLE had higher indices of mesenteric resistance than the normal controls, suggesting an abnormality of the mesenteric circulation even in those without overt signs of PLE. It is plausible to postulate that activation of the renin-angiotensin system with increased levels of circulating angiotensin II may be responsible for the increase in mesenteric vascular resistance seen after Fontan operation, thereby placing these patients at risk for development of PLE.