Semiquantitative characterization of dynamic magnetic resonance perfusion of the liver in pediatric Fontan patients

Abstract

Background Dynamic contrast-enhanced magnetic resonance imaging (MRI) of the liver in pediatric Fontan patients often shows peripheral reticular areas of hypoenhancement, which has not been studied in detail. Objective To semiquantitatively score the hepatic MR perfusion abnormality seen in pediatric Fontan patients, and to correlate the perfusion abnormality with functional clinical and hemodynamic parameters. Materials and methods All children (< 18 years old) after Fontan palliation with combined clinical cardiac and liver MRI performed between May 2017 and April 2019 were considered for inclusion. A semiquantitative perfusion score was used to assess the severity of the hepatic reticular pattern seen on dynamic contrast-enhanced liver imaging. The liver was divided into four sections: right posterior, right anterior, left medial and left lateral. Each liver section was assigned a score from 0 to 4 depending on the amount of abnormal reticular hypoenhancement. Scoring was assigned for each section of the liver across eight successive dynamic contrast-enhanced modified spoiled gradient echo runs. Scores were correlated with clinical and hemodynamic parameters. Results All Fontan children showed hepatic reticular hypoenhancement by MRI, most severe in the early portal venous phase with a median maximum total perfusion abnormality score of 12 (range: 9-14). All perfusion abnormalities progressively resolved during the hepatic venous phase. Perfusion abnormality scores were greatest in the right compared to left hepatic lobes (7 range: [6-8] vs. 5 [range: 3-6], P < 0.01). The maximum left hepatic lobe perfusion abnormality scores were greatest in children with versus without imaging signs of portal hypertension (8 [range: 7-8] vs. 4 [range: 3-5], P < 0.01). High unconjugated bilirubin and low platelets correlated with greater perfusion abnormality (R = 0.450, P = 0.024, and R = − 0.458, P < 0.01, respectively). Age at MRI, time from Fontan, focal liver lesions and cardiac MRI hemodynamic parameters did not show significant correlations with the severity of the liver perfusion abnormality. Conclusion All Fontan children have hepatic reticular hypoenhancement abnormalities seen with MRI that are most severe in the right hepatic lobe and universally show gradual resolution through the hepatic venous phase. Perfusion abnormality in the left hepatic lobe is worse in children with portal hypertension.

Fontan-associated liver disease: Diagnosis, surveillance, and management

“…Larger lesions, which are >10 mm in diameter, may have different presentations owing to background congestion of the liver tissue. Diffusion-weighted imaging may show a diverse presentation, sometimes with restricted diffusion, for nodules with otherwise benign features (Table 2) (43,96). These features may be in accordance with the Liver Imaging Reporting and Data System (LIRADS), which is frequently used to characterize and diagnose malignant liver lesions such as HCC (91).…”

“…Gadoxetic acid is partly excreted by the liver and complements enhancement information on the late hepatobiliary phase. The T2-weighted images frequently exhibit a diffusely increased liver signal intensity that might reflect the degree of congestion and patchy patterns on diffusion-weighted imaging (Figure 6) (43,63,96). For the Fontan circulation, the vascular contrast enhancement pattern on CT and MRI of the liver demonstrates a distinct peripheral, reticular, and patchy enhancement pattern during the late arterial and portal venous phases, which equilibrates with the background signal of the liver during the delayed phase (97).…”

Imaging of Fontan-Associated Liver Disease

“…11 The presence of these perfusion abnormalities in the left hepatic lobe has also been correlated with the presence of portal hypertension. 27 Extracellular contrast material equilibrates throughout the liver parenchyma over time resulting in a more homogenous appearance of the liver parenchyma on delayed-phase (3-5 minutes) images. Magnetic resonance imaging performed with hepatobiliary contrast agents may show a sharply contrasting reticular/serpiginous pattern of poor contrast retention in the hepatobiliary phase.…”

“…The distribution of the abnormal enhancement can be categorized as zonal (involving the periphery of the liver) or reticular (found diffusely throughout the liver), with the reticular pattern having been correlated with higher hepatic venous pressures and advanced fibrosis 11 . The presence of these perfusion abnormalities in the left hepatic lobe has also been correlated with the presence of portal hypertension 27 . Extracellular contrast material equilibrates throughout the liver parenchyma over time resulting in a more homogenous appearance of the liver parenchyma on delayed-phase (3–5 minutes) images.…”