Prospective Assessment of Ultrasound Shear Wave Elastography for Discriminating Biliary Atresia from other Causes of Neonatal Cholestasis.

OBJECTIVE: To prospectively assess the diagnostic performance of ultrasound shear wave elastography (SWE) and hepatobiliary laboratory biomarkers for discriminating biliary atresia from other causes of neonatal cholestasis. STUDY DESIGN: Forty-one patients <3 months of age with neonatal cholestasis (direct bilirubin >2 mg/dL) and possible biliary atresia were prospectively enrolled. Both 2-dimensional (2D) and point ultrasound SWE were performed prior to knowing the final diagnosis. Median 2D (8) and point (10) shear wave speed measurements were calculated for each subject and used for analyses. The Mann-Whitney U test was used to compare shear wave speed and laboratory measurements between patients with and without biliary atresia. Receiver operating characteristic curve analyses and multivariable logistic regression were used to evaluate diagnostic performance. RESULTS: Thirteen subjects (31.7%) were diagnosed with biliary atresia, and 28 subjects (68.3%) were diagnosed with other causes of neonatal cholestasis. Median age at the time of ultrasound SWE was 37 days. Median 2D (2.08 vs 1.49 m/s, P = .0001) and point (1.95 vs 1.21 m/s, P = .0014) ultrasound SWE measurements were significantly different between subjects with and without biliary atresia. Using a cut-off value of >1.84 m/s, 2D ultrasound SWE had a sensitivity = 92.3%, specificity = 78.6%, and area under the receiver operating characteristic curve (AuROC) of 0.89 (P < .0001). Using a cut-off value of >320 (U/L), gamma-glutamyl transferase (GGT) had a sensitivity = 100.0%, specificity = 77.8%, and AuROC of 0.85 (P < .0001). Multivariable logistic regression demonstrated an AuROC of 0.93 (P < .0001), with 2 significant covariates (2D ultrasound SWE [OR = 23.06, P = .01]; GGT [OR = 1.003, P = .036]). CONCLUSIONS: Ultrasound SWE and GGT can help discriminate biliary atresia from other causes of neonatal cholestasis.

Effect of Fontan operation on liver stiffness in children with single ventricle physiology.

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.

The VEGF receptor flt-1 (VEGFR-1) is a positive modulator of vascular sprout formation and branching morphogenesis.

Sprouting angiogenesis is critical to blood vessel formation, but the cellular and molecular controls of this process are poorly understood. We used time-lapse imaging of green fluorescent protein (GFP)-expressing vessels derived from stem cells to analyze dynamic aspects of vascular sprout formation and to determine how the vascular endothelial growth factor (VEGF) receptor flt-1 affects sprouting. Surprisingly, loss of flt-1 led to decreased sprout formation and migration, which resulted in reduced vascular branching. This phenotype was also seen in vivo, as flt-1(-/-) embryos had defective sprouting from the dorsal aorta. We previously showed that loss of flt-1 increases the rate of endothelial cell division. However, the timing of division versus morphogenetic effects suggested that these phenotypes were not causally linked, and in fact mitoses were prevalent in the sprout field of both wild-type and flt-1(-/-) mutant vessels. Rather, rescue of the branching defect by a soluble flt-1 (sflt-1) transgene supports a model whereby flt-1 normally positively regulates sprout formation by production of sflt-1, a soluble form of the receptor that antagonizes VEGF signaling. Thus precise levels of bioactive VEGF-A and perhaps spatial localization of the VEGF signal are likely modulated by flt-1 to ensure proper sprout formation during blood vessel formation.