Abstract

Background: Several studies in adults showed that spleen stiffness measurement (SSM) by vibration-controlled transient elastography (VCTE) can accurately assess clinically significant portal hypertension (HTN) and predict presence of esophageal varices. However, pediatric studies on SSM published thus far have used a liver-specific probe to measure the spleen making them difficult to interpret and possibly overestimating SSM, as the spleen is inherently a stiffer organ than the liver. The new dedicated spleen stiffness examination of the FibroScan® 630 uses a higher shear wave frequency (100 Hz v. 50 Hz) and can measure to a higher SSM (100 kPa v 75 kPa) compared to the liver-specific one. Given unique measurement challenges in children and lack of pediatric data, we aimed to conduct a feasibility study to assess SSM with the new spleen-dedicated examination in a cohort of pediatric patients.

Methods: We conducted a prospective pilot study enrolling patients with chronic liver disease aged 5-30 years followed at Boston Children’s Hospital. Subjects underwent SSM by VCTE with the spleen-dedicated examination on the M probe (FibroScan® 630) and liver stiffness measurement (LSM) by conventional VCTE. Laboratory data were collected if obtained within 1 month of SSM.

Results: 152 patients (67% male) with median age 15 years [IQR 11, 18] were enrolled. Most common liver disorders were NAFLD (44%), viral hepatitis (10%), and biliary atresia (6%). Median weight was 68.8 kg [IQR 50, 88]. Laboratory data showed median [IQR] ALT 39 IU/L [20, 69], GGT 27 IU/L [17, 45], albumin 4.6 g/dL [20, 69], direct bilirubin 0.2 mg/dL [0.2, 0.2], INR 1.02 [0.94, 1.07], and platelet count 268 x10⁹/L [211, 312, 13% <150]. Thirteen percent of patients had a palpable spleen on exam. LSM was successfully obtained in 142 patients using a S1 (1%), M (77%) and XL probe (22%). Median LSM value was 5.5 kPa [IQR 4.7, 7.4] (15.5% LSM >8.6 kPa); median CAP score was 239 [IQR 191, 291]. SSM was successfully obtained in 146 (96%) patients with an overall failure rate of 4% due to a high skin-to-capsule distance. Median SSM was 18.5 kPa [IQR 13.7, 25] and 11 (7.5%) patients had a SSM ≥40. SSM significantly correlated with LSM (p <0.001; Pearson coefficient 0.3) [Fig.], AST (p<0.001), ALT (p<0.001) and GGT (p=0.001).

Conclusion: This is the first study to show feasibility and extremely high success rate of the novel spleen-dedicated examination to measure SSM in children. With such spleen specific acquisition settings, feasibility and correlation to LSM, the novel spleen-dedicated SSM examination is a promising, more accurate tool to monitor for the evolution of portal HTN and its complications in children with liver disease.