Having read with interest the letter published by Martínez-Quintana et al. concerning my publication,1 I would like to add some comments on liver imaging findings after Fontan surgery.
First, ultrasonography is the most commonly used imaging technique for initial and follow-up liver evaluation in these children, mainly due to the lack of radiation. Hepatic parenchymal changes after the procedure, known as Fontan-associated liver disease, include liver fibrosis and cirrhosis and hepatocellular carcinoma. Although ultrasonography usually detects late changes of fibrosis and cirrhosis (such as heterogeneous parenchymal echotexture or surface nodularity), recent publications show that other findings, such as hyperechoic lesions without surface nodularity detected by high frequency transducer, may represent the early stage of fibrosis.2 These lesions were not demonstrated by computed tomography or magnetic resonance imaging and most patients (82%) showed normal biochemical hepatic function tests, despite the presence of hepatic parenchymal changes on imaging.2
Second, recent studies suggest that, considering that congestion is the primary or sole trigger of liver fibrosis in these patients, ultrasound elastography may eventually become a useful noninvasive, low-cost proxy assessment of Fontan hemodynamics and a clinical means of determining which patients are at highest risk of fibrosis development.3 Moreover, magnetic resonance elastography might prove particularly useful to evaluate progression of liver disease and have important prognostic value.4 Furthermore, some authors conclude that magnetic resonance elastography allows earlier detection of fibrogenesis than biomarkers.5
Finally, with regard to contrast computed tomography and magnetic resonance imaging, heterogeneous enhancement is a common finding in cirrhotic liver. Hypervascular liver nodules are an additional important finding in patients with longstanding Fontan circulation (20%-30%), also known as focal nodular hyperplasia-like lesions.4 The main differential diagnosis of hypervascular nodules in a cirrhotic liver should be hepatocellular carcinoma but there are few reported cases of hepatocellular carcinoma in these patients.4 In fact, according to a recent publication, there are only 11 case reports of hepatocellular carcinoma after the Fontan procedure in PubMed.6
In conclusion, although ultrasonography and laboratory screening at regular intervals should be the first-line tests in the long-term evaluation of these patients, elastography and contrast studies are useful tools that should also be considered in follow-up.