Spleen stiffness measurements by acoustic radiation force impulse imaging after living donor liver transplantation in children: a potential quantitative index for venous complications

Ultrasound innovations in abdominal radiology: techniques and clinical applications in pediatric imaging

Contrast-enhanced ultrasound, microvascular imaging, elastography, and fat quantification have varying degrees of utility, with some applications in the pediatric setting mirroring that in adults and having unique uses when applied to children in others. This review will present novel ultrasound technologies and the clinical context in which they are applied to the pediatric abdomen. New ultrasound technologies have a broad range of applications in clinical practice and represent a powerful diagnostic tool with the potential to replace other imaging modalities, such as magnetic resonance imaging and computed tomography, in specific cases.

Ultrasound Elastography in Children

Ultrasound elastography is a novel ultrasound technique, being extensively researched in children in the last decade. It measures tissue elasticity with the observation of tissue response after an external stimulus. From research to clinical practice, ultrasound elastography has evolved significantly in liver fibrosis evaluation in children; however, several other applications of the technique are available in both clinical practice and research environments. Practically, in children any organ can be assessed, including the brain in early ages, along with muscle and connective tissue elasticity evaluation, spleen, kidney, skin, lymphatic tissue, etc. The elastography method, age, body mass index and technical points should be considered when performing ultrasound elastography. This review highlights its vast potential as a diagnostic tool in the pediatric population, where ultrasound is a dominant imaging tool; however, the indications and exam protocol for its clinical use in several fields in pediatrics have yet to be elucidated.

Acoustic radiation force impulse imaging: normal values of spleen stiffness in healthy children

BACKGROUND

Acoustic radiation force impulse (ARFI) imaging is a noninvasive ultrasound elastography technique for evaluating tissue stiffness. The association of liver and spleen stiffness provides additional information in the assessment of portal hypertension. The technique and normal values of spleen stiffness by point shear wave elastography (p-SWE) in pediatrics have not been well documented.

OBJECTIVE

Our aim is to describe the feasibility and normal ARFI elastography values in the spleen for healthy children and to compare measurements in two different probe positions (the axial and sagittal planes).

MATERIALS AND METHODS

Spleen p-SWE using ARFI values were measured with a 6C1 probe in 102 healthy children (age range: 8 weeks to 17 years) divided into four age groups. An average of nine (standard deviation: two) spleen stiffness measurements were taken during free breathing in each plane (axial and sagittal). The impact of age and measurement plane in the spleen was analyzed using multivariate models.

RESULTS

There was no significant difference in spleen stiffness values taken at different ages, with an average of the medians of 2.43±0.31 m/s. There was no significant difference based on probe orientation: sagittal plane (median: 2.46±0.29 m/s) and axial plane (median: 2.43±0.32 m/s) with Student's t-test P=0.18. The mean depth of measurement varied between 2.3 cm and 3.7 cm, according to age.

CONCLUSION

Normal spleen stiffness values using ARFI imaging in children do not vary with age and correspond to a median of 2.43 m/s. No significant difference was found when using different probe positions.

Liver Graft and Spleen Elastography After Living Liver Transplantation: Our First Results

AIM OF THE STUDY

Liver transplantation is widely applied as a standard and effective management of end-stage liver diseases, hepatocellular carcinoma, and acute liver failure. Investigation of morphologic and functional changes in the transplanted graft, gastrointestinal system, and spleen after transplantation is an important ground for assessment of post-transplantation results, early changes related to complications, and evaluation of response to treatment modalities. The aim of this study was to investigate the dynamics of changes in elastography of the liver graft and spleen after living-related liver transplantation.

MATERIAL AND METHODS

The study included 14 cirrhotic patients after living-related liver graft transplantation. Stiffness of the spleen and liver was evaluated before transplantation and at 1, 3, and 6 months after transplantation with a Supersonic Aixplorer Multi Wave device. Each procedure consisted of measuring the density in 10 points (spots) of the organ. The final result was calculated as the mean value of successful measurements (must have been > 60% of all measurements) and expressed in kilopascals.

RESULTS

The mean value of the liver and spleen stiffness before transplantation was 27 kPa (14-31 kPa) and 51 kPa (38-92 kPa), respectively. The stiffness of the spleen gradually reduced after transplantation to 40.3, 35.4, and 24.1 kPa (P = .001) at 1, 3, and 6 months. The stiffness of the liver graft in patients without complications was stable at 4-5 kPa, whereas the same value in patients with complications was increased (≥ 7.5 kPa). In 5 patients, endoscopic investigation confirmed the significant reduction of varicose veins after surgery.

CONCLUSION

Elastography of the liver graft and spleen after liver transplantation can be recommended as a useful-for-patient 1-off method of investigation.

Doppler ultrasound in the diagnosis of Budd-Chiari syndrome in children after split liver transplantation

PURPOSE

To assess the capabilities of a velocity ratio>3 for the diagnosis of Budd-Chiari syndrome (BCS) in children after split liver transplantation using Doppler ultrasonography (DUS).

MATERIALS AND METHODS

A total of 28 children who underwent liver transplantation using a split procedure were included. There were 11boys and 17girls with a mean age of 3.8years (range: 0.7-12years). Velocity ratio between blood velocity upstream of the anastomosis and that at the level of the inferior vena cava anastomosis was calculated. Sensitivity, specificity and accuracy of DUS for the diagnosis of BCS were estimated using a velocity ratio>3.

RESULTS

Eight children (8/28; 29%) had BCS and 20 (20/28; 71%) did not have BCS using the standard of reference. A velocity ratio>3 on DUS yielded 88% sensitivity (95% CI: 53-98%), 80% specificity (95% CI: 58-92%) and 82% accuracy (95% CI: 64-92%) for the diagnosis of BCS.

CONCLUSION

A velocity ratio>3 on DUS is a reliable finding for the diagnosis of BCS in children after split liver transplantation.