This paper presents the preoperative imaging strategies derived from a multicenter European survey, which examines the current practices in pediatric liver transplantation imaging. The survey provides a comprehensive, multidisciplinary perspective on how imaging is integrated into the overall assessment of children with end-stage liver disease. Data were collected from 22 European centers, encompassing over 1,500 pediatric liver transplantations conducted over a 3-year period. As a result, the findings offer a representative overview of the prevailing imaging practices in this context. Details of the current use of imaging methods during the intra- and postoperative phase will be provided in dedicated publications of the results of this survey.

All sites use US to assess and monitor children before liver transplantation. Two-thirds of sites also consider US as their preferred and main imaging modality to outline anatomy and plan surgery. Especially in infants and lean children, Doppler US is feasible and highly accurate to detect arterial and venous abnormalities at the preoperative stage [12, 15]. The sites indicating US as their primary modality will only add further cross-sectional imaging if clarification is needed, e.g., to define vascular abnormalities suspected on US that may potentially complicate the transplantation, lesion characterization as part of oncologic staging, or prior surgery that increases the risk of unexpected findings.

The rather selective use of preoperative CT or MRI is explained by the high proportion of very young children qualifying for liver transplantation (70%<6 years of age), in keeping with previous publications [16]. Younger children have a higher sensitivity for the consequences of ionizing radiation [17,18,19]. In addition, depending on the CT machine and local preference, young children may require general anesthesia for CT. For MRI, the feed and wrap method may be used to avoid general anesthesia in children 0–6 months old, but anesthesia will generally be required between 6 months and 6 years [20, 21]. Nevertheless, one-third of the pediatric transplantation sites always perform contrast-enhanced CT in children awaiting liver transplantation. Their common indication is delineation of the child’s vascular anatomy, essentially representing the backbone for later transplantation. CT angiography can depict vascular anatomy also in young children with very high accuracy and may be the best method to show subtle hepatic artery anomalies [5, 14].

This survey revealed substantial differences regarding the basic CT scan parameters used at the centers. The majority of centers imaged the entire abdomen, whereas a quarter limited their CT scans to the upper abdomen only. The number of contrast phases usually applied at each center varied between one and four. This suggests the potential for further dose saving. A split bolus technique, for example, generates high contrast images of all hepatic vessels in one CT phase, omitting the need for additional acquisitions [22, 23]. This technique has also been evaluated in the context of pediatric trauma, oncologic disease for characterization of focal liver lesions in adults, and renal donor evaluation [24,25,26].

Abdominal MRI, which is a radiation-free alternative to CT, is regularly used by those transplantation sites not primarily relying on CT at the preoperative stage. The most frequent indication is lesion characterization for which hepatic MRI is the method of choice, offering dynamic imaging and liver-specific contrast agents (in some countries off-label) [27,28,29,30]. Compared to CT, fewer centers use abdominal MRI to image vascular anatomy. The most applied technique is 3-DMRA which may show slightly inferior accuracy to CT angiography for depiction of arterial anatomy as suggested by adult and a few pediatric studies [5, 14, 31]. However, with newer MRI techniques (e.g., 3-tesla MRI, time-resolved contrast-enhanced MRA), the state-of-the-art techniques may change soon and should be the object of future comparative studies [14].