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Effect of Fontan operation on liver stiffness in children with single ventricle physiology
Frank W DiPaola1, Kurt R Schumacher2, Caren S Goldberg2
1Division of Pediatric Gastroenterology, Department of Pediatrics, C.S. Mott Children's Hospital, University of Michigan Health System, 1500 East Medical Center Drive, Ann Arbor, MI, 48109, USA. dipaolaf@med.umich.edu.
Insights
The Fontan operation causes immediate and lasting increases in liver stiffness and IVC pressure in children. This suggests that hepatic congestion, not fibrosis, is the primary driver of early liver stiffening post-surgery.
Area of Science:
- Pediatric Cardiology
- Hepatology
- Medical Imaging
Background:
- The Fontan operation is a complex surgical procedure for single-ventricle congenital heart defects.
- Fontan-associated liver disease (FALD) is a significant long-term complication, characterized by hepatic fibrosis and cirrhosis.
- Non-invasive methods to assess liver health in these patients are crucial for early detection and management.
Purpose of the Study:
- To evaluate changes in liver stiffness using ultrasound point shear wave elastography (US P-SWE) in children before and after the Fontan operation.
- To correlate liver stiffness measurements with inferior vena cava (IVC) pressure.
- To investigate the role of hepatic congestion in early liver stiffening post-Fontan.
Main Methods:
- Prospective enrollment of 18 children undergoing the Fontan operation.
- Serial US P-SWE measurements of liver stiffness (shear wave speed, SWS) in the right hepatic lobe.
- Collection of contemporaneous inferior vena cava (IVC) pressure data.
- Statistical analysis using mixed-effect models and Wilcoxon signed-rank test.
Main Results:
- Mean liver SWS significantly increased from baseline (1.18 m/s) immediately post-operation (2.28 m/s at ~2.5 days) and remained elevated at chronic time points (~185 days, 2.08 m/s).
- Mean IVC pressure also significantly increased post-operatively (~16.44 mmHg) compared to baseline (~7.2 mmHg).
- Elevated liver stiffness correlated with increased IVC pressure, indicating hepatic congestion.
Conclusions:
- The Fontan operation induces immediate and sustained hepatic congestion, leading to increased liver stiffness.
- Early increases in liver stiffness post-Fontan are primarily driven by congestion rather than fibrosis.
- Congestion significantly impacts US P-SWE measurements, potentially confounding its use as a sole biomarker for liver fibrosis in this population.
Objectives:
Assess liver stiffness using ultrasound point shear wave elastography (US P-SWE) in children before and after the Fontan operation.
Methods:
Eighteen children undergoing the Fontan operation were prospectively enrolled. Eight US P-SWE measurements were obtained from the right hepatic lobe before surgery, and at multiple postoperative time points. Temporally related inferior vena cava pressure (IVC) data was collected from medical records, when available. Changes in mean liver shear wave speed (SWS) were assessed using a mixed-effect model with post hoc Tukey correction. Changes in IVC pressure were evaluated using the Wilcoxon signed-rank test. A p value less than 0.05 was considered significant.
Results:
Mean age at enrolment was 33.5 ± 10.5 months. Baseline mean liver SWS was normal at 1.18 ± 0.29 m/s, increased to 2.28 ± 0.31 m/s at 2.5 ± 1.2 days (p < 0.0001) and to 2.22 ± 0.38 m/s at 7.5 ± 1.4 days (p < 0.0001). Five subjects returned at a mean of 185 ± 28 days, and mean liver SWS remained elevated at 2.08 ± 0.24 m/s (p < 0.0001). Mean IVC pressure increased from 7.2 ± 2.6 mmHg at baseline to 16.44 ± 3.3 mmHg at 2.2 ± 0.8 days post-surgery (p = 0.004).
Conclusion:
The Fontan operation immediately and chronically increases liver stiffness and IVC pressure. Our study provides further evidence that congestion is a key driver of Fontan-associated liver disease.
Key Points:
• The Fontan operation triggers immediate hepatic congestion and marked liver stiffening. • Congestion, not fibrosis, drives early increased liver stiffness in Fontan patients. • Hepatic congestion persists chronically for months after the Fontan operation. • Congestion confounds shear wave elastography as a post-Fontan liver fibrosis biomarker.
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