Large-for-size syndrome is a rare but devastating condition that can interfere with the survivals of both the graft and the recipient 6. During deceased donor liver transplantation (DDLT), the size mismatch between the donor’s liver and recipient’s abdominal cavity can occur due to the limited evaluation of both the donor and recipient 7. Although the chance is low, since CT scan is not a routine evaluation procedure for deceased donors in Republic of Korea for protecting the kidney from contrast-induced kidney injury, there is a risk for the occurrence of large-for-size syndrome especially in small female recipients matched to male donors. The decision to perform LT using the graft or to reduce the graft should be decided based on the understanding of the size of the recipient’s abdominal cavity. However, in most cases, the donor and recipient are operated in different hospitals. Therefore, the donor surgeon should decide whether the graft is in adequate size based on the visual examination of the graft liver without actual visual comparison of the recipient’s abdominal cavity. Since large-for-size syndrome is rare, there were only limited published studies 8. By calculating the diameter of the right hemi-abdomen where the liver will be placed can be helpful for the decision. However, while experienced surgeons can manage to perform adequate decision making with limited information, surgeons in their learning curve needs more assistance not to make a mistake during the decision process. Therefore, we managed to utilize 3-D printing technology to build a 3-D printed model of the intra-abdominal cavity to its actual size.
3-D printing technology has been applied to the field of liver surgery and several studies has been published since 3,9. However, most studies focused on liver malignancy with an effort to print the location of the cancer as well as the anatomical structure 10-12. These approaches seem valuable in that it can print with the exact size of the liver and cancer mass. However, since 3-D reconstruction without 3-D printing can also give advanced view to the surgeon, whether the 3-D printing significantly enhances the surgeon’s insight is questionable, especially when time and cost of the 3-D printing is taken into account. 3-D printing in LT was first introduced in the literature of Zien et al 13. In the study, the surgical team printed the graft liver as well as the recipient’s original liver and compared it to the actual livers. The study was promising for transplant clinicians of which it showed high accuracy with high resemblance of the 3-D printed model with the graft. However, how to use the technology was up to the clinicians. The study published by Wang et al 14, showed that 3-D printing technology can be used in pediatric LT for surgical planning. The surgical team printed the abdominal cavity and planned liver graft and evaluated whether the surgery can be performed safely. The outcome showed that 3-D printing can be practically used in during clinical practice.
Our 3-D model protocol was originally planned to be used for small donors who might accept large liver graft during DDLT. Therefore, the key to success was to print the model as fast as possible with low cost. We prepared 3-D printed model of the intra-abdominal cavity in advance for the patients with high MELD scores, who are expected to undergo DDLT. Nevertheless, there are times when allocation and transplantation occur abruptly. Case No.14 (Table 2) was an example of which the transplant surgeon requested for a 3-D printed model 6 hours before surgery. Therefore, we planned a 3-D model with a wider slice distance which reduced printing time. This showed the possibility that our protocol could be much more time-saving in the future.
Three cases were performed successfully with modification of the protocol. During the three cases, one cases required a reduction graft which fit perfectly to the small abdominal cavity. After the three cases, we designed a prospective study to use the 3-D printed model in potential adult recipients in the waiting list with small intra-abdominal cavity and pediatric LT recipients. Our protocol was not to mimic every detail of the human body or liver graft, but only focused on the actual size of cavity and graft. The 3-D printed model was used for comparing the size of the graft to the recipient’s intra-abdominal cavity during deceased donor harvest operation. Decision to receive, either whole liver or after reduction, or to withdraw the chance was made by the donor surgeon with the assistance of the 3-D printed model. After back-table procedure, evaluation for the fitness was done and every case fitted properly to the 3-D model as well as the actual recipient’s cavity.
Pediatric LT cases were also good candidate for 3-D printing. Unlike adult recipients, 3-D printing was done on both hemi-abdomens. Liver grafts, whether it was left hemi-liver, extended left lateral liver, or reduced liver graft of extended left lateral liver, were printed as the surgeon’s plan. The actual liver grafts were used as the original planned and two cases needed a reduction graft as the original planning from the 3-D printed models.
The case presented in Figure 3E was a perfect situation where 3-D printed model can be beneficial. In a patient with a distorted space, well-matched GRWR can be a misleading factor that can lead to devastating situation of large-for-size syndrome. The space of the patient’s right liver fossa which underwent contracture after chronic empyema, was somewhat similar to the 8-year-old female recipient’s liver fossa presented in Table 2. The GRWR of the donor’s right liver was 1.63 while the actual printed right liver far exceeded the spatial boundaries of the 3-D printed abdominal cavity.
As data presented in Table 1, adult recipients and pediatric recipients have distinct characteristics. The different characteristics requires different management from the surgical teams. 3-D printing for the patients also different between adult and pediatric patients. While adult recipients mostly required printing of the right hemi-abdomen, pediatric patients required printing of the entire abdomen. Slice distance was significantly narrower in the pediatric recipients. However, the fundamental process for manufacturing the 3-D printed model is similar and time and amount of filaments required was similar between the two groups. This shows that our 3-D printing protocol can be utilized properly for both adult and pediatric recipients with minimal error.
The limitation of this study is that our study only showed descriptive data of our patients whose abdominal cavity was 3-D printed. This study did not show a comparative data with a control group to compare the impact of using 3-D printed model. The reason for not showing a comparative data is that the patients who are expected to benefit from 3-D printing is apparently patients whose abdominal cavity have a potential to be small and were selected to be prepared by our 3-D imaging and printing laboratory. Even though our 3-D model simulates the patient's intra-abdominal space, it has a drawback in that our model does not reflect the actual elasticity of the abdominal wall and diaphragm. This could lead surgeons to be conservative while making decision whether the real graft fit to the recipient. The surgeon’s should take into account the elasticity of the muscular structures comprising the liver fossa when making a decision to proceed for transplantation based on our 3-D printed model.
In general, when height and weight are not so different between the donor and recipient, the graft liver usually fits into the recipient’s abdominal cavity. However, in small patients, predominantly female, there lies a risk of large-for-size syndrome when they are allocated to a deceased donor. Among seven adult patients of our study, five patients were managed to pivot from the initial plan established before deceased donor operation; Two patients were transplanted later with another donor due to large-sized graft, one patient was decided to undergo reduction of the original graft; one patient was decided to receive a whole liver while the initial plan was to perform a reduction hepatectomy, and one patient was decided to receive liver graft from living donor after deciding not to use a pre-allocated deceased donor graft. Although the other two recipients received a whole liver as initially planned, the donor surgeon took into account the 3-D printed intra-abdominal cavity.
In pediatric LT, large-for-size syndrome can occur, especially younger patients with lower weight. Among five pediatric patients, two patients were decided to undergo reduction of the original graft after actual fitting of donor graft to 3-D printed model of recipients. The other three patients also underwent LT as initially planned after fitting the donor graft to the 3-D printed model. All donor grafts suited perfectly to the recipients’ abdominal cavity and resulted in successful transplantation without having difficulty in closing abdominal wall of recipients.
Nevertheless, our 3-D printing protocol enabled fast printing with low cost, which is essential for emergency operation such as deceased donor LT. The median manufacturing times were 568 minutes and 601 minutes for adult and pediatric recipients, respectively. Since most of time is consumed during 3-D printing, the time can be shortened if multiple 3-D printers are used simultaneously or number of slices are lowered. The time consumed for printing the expected liver graft was 25 to 40 hours according to the study of Zein et al. From the study of Wang et al., the cost for printing the half-sized model of abdominal cavity and liver graft was 929.6 US dollars and required approximately 48 hours for printing. Compared to the previous studies, our simplified 3-D printing model showed far superior feasibility in time and cost. Another strength of our model is that our protocol only requires a fused deposition modeling type 3-D printer, which is cheaper and does not require special facility. The strength can allow many transplantation centers to utilize the protocol for fast use in emergency cases.
Recipients such as small women and children under 1-year old with acute liver failure without hepatomegaly are expected to have small abdominal cavity leading to large-for-size-syndrome. Our protocol may be very helpful especially for those recipients’ LT. To minimize the occurrence of large-for-size syndrome, 3-D printing of the intra-abdominal cavity of the recipient can be a feasible option.