One liver for two: partition of the portal elements

A systematic review and meta-analysis of portal vein morphometry in pediatric and adult populations: Drawing the line between normal and abnormal findings

PURPOSE

The morphometry of the hepatic portal vein is of clinical importance, particularly in pre-operative assessments, surgical management, and diagnoses of liver conditions. This systematic review and meta-analysis aimed to characterize the morphometry of the normal portal vein in both pediatric and adult patients.

METHODS

The study, conducted using the PRISMA guidelines and registered with PROSPERO, utilized the MEDLINE, EMBASE, SCOPUS and Web of Science databases up to May 2020, and updated to May 2023. All studies reporting extractable data on diameter, length, and cross-sectional area (CSA) of the main, left, and right portal veins (PV, LPV, RPV, respectively) were included. The AQUA Tool was used to assess the quality of the included studies. Data analysis included subgroup analyses based on geographical location, sex, age, and imaging modality.

RESULTS

A total of 122 studies with 11,637 subjects were eligible for inclusion. Overall, the pooled mean diameter of the PV (PVD) was 10.09 mm (95% CI: 9.56-10.62). Significant differences in diameter were found between pediatric (6.60 mm; 95% CI: 5.38-7.82) and adult (10.72 mm; 95% CI: 10.25-11.19) subjects. Additionally, there was a significantly larger PVD measurement from computed tomography (CT) than other imaging modalities: CT, 13.28 mm (95% CI: 11.71-14.84); magnetic resonance imaging (MRI), 10.50 mm (95% CI: 9.35-11.66) and ultrasound (US), 9.81 mm (95% CI: 9.47-10.16). The mean diameters of the LPV and RPV were 8.27 mm (95% CI: 6.78-9.77) and 8.33 mm (95% CI: 6.70-9.95), respectively. Mean PV length in adults is 48.63 mm (95% CI: 35.63-61.64). Mean CSA of the PV was 1.09 cm2.

CONCLUSIONS

The study obtained aim to improve the understanding of portal vein anatomy, especially with relevance to surgical interventions of the liver in both pediatric and adult patients. Measurements from ultrasound imaging closely approximates the generated pooled PVD mean for pediatric and adult patients. CT imaging, however, significantly exceeded the established 13 mm threshold for adults. For pediatric patients, a threshold of 8 mm is proposed as a diagnostic upper limit for a normal PVD. Although not significant, the PVD decreased from the portal confluence towards its bifurcation.

Reducing the shortage of donor livers: what would It take to reliably split livers for transplantation into two adult recipients?

This article examines the scientific, technical, and administrative barriers to splitting donor livers for use in two adults. The main scientific barrier is that cadaveric donor livers at their current level of postoperative function are not sufficiently large to support life in two adult recipients. However, glycogenation of livers from young donors may be a method to overcome this problem in the short term. The three technical obstacles to splitting the liver in the midplane are anatomic anomalies that complicate or prevent splitting, the means to detect these anomalies, and the surgical methods to accomplish the split. Anatomic anomalies affecting the biliary drainage and arterial supply of the liver are the most important limiting technical factors. Administrative accommodations in the current methods of organ allocation will be needed if split-liver transplantation in adults is to succeed. A nationwide view of organ allocation requires that the total number of lives saved by the procedure be the priority outcome nationally. If liver transplantation is viewed from this perspective, split-liver transplantation for adults would be a high priority, and incentives should be set to encourage it.

Three-dimensional reconstruction of the liver venous system using the preservation solution as contrast agent

To investigate whether MRI without using artificial contrast agents can provide sufficient image contrast to visualize the venous tree in the cold stored liver graft, two pig liver grafts were scanned with a multislice turbo spin-echo sequence with long TE (200 msec). The quality of the data obtained at 1-T field strength was sufficient for three-dimensional reconstruction of the hepatic vascular system, potentially useful for liver splitting surgery.

Magnetic resonance venography in liver bipartition procedures using preservation solution as contrast agent

To evaluate whether the hepatic veins can be visualized with a rapid noninvasive technique, and if so, whether the obtained images could be helpful in the preparation of split liver grafts for transplantation, six cold stored human donor livers were investigated with magnetic resonance imaging (MRI). The hepatic vein branches and their confluence were clearly visualized. Anatomic variations of the middle hepatic vein with consequences for the choice of the transection plane could be demonstrated. Furthermore, unexpected vascular abnormalities were detected. From these preliminary results it is concluded that visualization of the hepatic veins can be helpful in determining the feasibility of the bipartition procedure and the choice of the transection plane. A potential wide application of this fast and noninvasive technique is possible.