Predicting gastroesophageal varices through spleen magnetic resonance elastography in pediatric liver fibrosis

Abstract

Background: A recent retrospective study confirmed that hepatic stiffness and splenic stiffness measured with magnetic resonance elastography (MRE) are strongly associated with the presence of esophageal varices. In addition, strong correlations have been reported between splenic stiffness values measured with MRE and hepatic venous pressure gradients in animal models. However, most studies have been conducted on adult populations, and previous pediatric MRE studies have only demonstrated the feasibility of MRE in pediatric populations, while the actual clinical application of spleen MRE has been limited.

Aim: To assess the utility of splenic stiffness measurements by MRE to predict gastroesophageal varices in children.

Methods: We retrospectively reviewed abdominal MRE images taken on a 3T system in pediatric patients. Patients who had undergone Kasai operations for biliary atresia were selected for the Kasai group, and patients with normal livers and spleens were selected for the control group. Two-dimensional spin-echo echo-planar MRE acquisition centered on the liver, with a pneumatic driver at 60 Hz and a low amplitude, was performed to obtain hepatic and splenic stiffness values. Laboratory results for aspartate aminotransferase to platelet ratio index (APRI) were evaluated within six months of MRE, and the normalized spleen size ratio was determined with the upper normal size limit. All Kasai group patients underwent gastroesophageal endoscopy during routine follow-up. The Mann-Whitney U test, Kendall's tau b correlation and diagnostic performance analysis using the area under the curve (AUC) were performed for statistical analysis.

Results: The median spleen MRE value was 5.5 kPa in the control group (n = 9, age 9-18 years, range 4.7-6.4 kPa) and 8.6 kPa in the Kasai group (n = 22, age 4-18 years, range 5.0-17.8 kPa). In the Kasai group, the APRI, spleen size ratio and spleen MRE values were higher in patients with portal hypertension (n = 11) than in patients without (n = 11) (all P < 0.001) and in patients with gastroesophageal varices (n = 6) than in patients without (n = 16) (all P < 0.05), even though their liver MRE values were not different. The APRI (τ = 0.477, P = 0.007), spleen size ratio (τ = 0.401, P = 0.024) and spleen MRE values (τ = 0.426, P = 0.016) also correlated with varices grades. The AUC in predicting gastroesophageal varices was 0.844 at a cut-off of 0.65 (100% sensitivity and 75% specificity) for the APRI, and 0.844 at a cut-off of 9.9 kPa (83.3% sensitivity and 81.3% specificity) for spleen MRE values.

Conclusion: At a cut-off of 9.9 kPa, spleen MRE values predicted gastroesophageal varices as well as the APRI and spleen size ratio in biliary atresia patients after the Kasai operation. However, liver MRE values were not useful for this purpose.

Keywords: Biliary atresia; Kasai operation; Magnetic resonance elastography; Portal hypertension; Splenic stiffness.

Figure 1

Box-and-whisker plots for the comparison of varices grades. The graphs are shown for (A) the aspartate aminotransferase to platelet ratio index (APRI) and (B) spleen magnetic resonance elastography (MRE) values according to the grade of gastroesophageal varices. Among the different varices grades, there were significant differences in the APRI (P = 0.029) and spleen MRE values (P = 0.045), but not in the spleen size ratio (P = 0.084) or liver MRE values (P = 0.795). MRE: Magnetic resonance elastography; APRI: Aspartate aminotransferase to platelet ratio index.

Figure 2

Liver magnetic resonance imaging of biliary atresia patients with different varices grades. Liver magnetic resonance imaging images are shown from three respective patients with grade 0 (first row), grade 1 (second row) and grade 2 (third row) gastroesophageal varices, including (A) axial single-shot fast spin-echo T2-weighted images, (B) magnitude images and (C) post-processed shear stiffness maps with color-coded elastograms from 0 to 20 kPa. The elastograms display the progressively increasing splenic stiffness in these patients.

Figure 3

Comparison of area under the curve analyses for predicting varices. The area under the curve was 0.844 for the aspartate aminotransferase to platelet ratio index (cut-off, 0.65), 0.813 for the spleen size ratio (cut-off, 1.08) and 0.844 for the spleen magnetic resonance elastography values (cut-off, 9.9 kPa) for predicting gastroesophageal varices. The diagnostic performance did not differ among these three methods. APRI: Aspartate aminotransferase to platelet ratio index.