The shortage of organ donors for low-weight liver transplant recipients, especially small children, has led to the development of new surgical techniques to increase the donor pool. Almost all of these techniques use the left lateral segment (Couinaud's segments II and III), but even this graft could be too large for children under 10 kg, and further reduction could be necessary. Few articles address the issue of monosegmental liver transplantation. Available articles are with small sample sizes or even case reports, which makes it difficult to draw conclusions about indication and outcome for monosegmental grafts. A search of the MEDLINE databases using the terms “Liver Transplantation” and “Monosegmental” or “Monosegments” limited to title or abstract with publication in the English language was conducted. The data from each study were selected and analyzed, regarding donor status (living or cadaveric), donor weight, surgical techniques used in left lateral further reduction, recipient indication for liver transplantation, age and recipient weight, graft-to-recipient body weight ratio, segment utilized, type of abdominal closure, postoperative complications, and survival. Seven publications were identified from 1995 to 2004 and fulfilled the criteria. A total of 27 pediatric patients who received a monosegment transplant were identified, median age 211 days (range, 27 to 454 days) and median weight 4.6 kg (range, 2.45 to 7.4 kg). Segment III was utilized in 21 (78%) and segment II in 6 (22%). Patient survival was 85.2%. In conclusion, monosegment liver transplantation appears to be a satisfactory option for infants weighing less than 10 kg who require a liver transplant. (Liver Transpl 2005;11:564–569.)
The first liver transplant in a human was performed in a 3-year-old child 40 years ago. However, the development of pediatric liver transplantation has been associated with the introduction of some techniques to solve the problem of disparity between available donors and the exponential increase of patients on the waiting list. Reduced-size, split-liver, and living related donors are all capable of reducing the deficit of organs for pediatric patients.1–4
Almost all of these techniques use the left lateral segment (Couinaud's segments II and III) of the liver, but this graft may be too large for infants under 10 kg. To overcome a weight discrepancy of more than 10:1 from donor to recipient, a further reduction of the left lateral segment to a monosegment may be necessary, as has been done with cadaveric5–8 and living related donors (LRD).9–13 The subsequent reduction could be performed in situ, at the donor operation7, 9, 12 or at the back table procedure,5, 6, 8 with the utilization of the segment II6, 8, 9 or III5, 7, 12, 13 as grafts. The small sample size of reported data from each study on monosegmental liver transplantation (MLT), different donor status (cadaveric or living), and technical reduction of segment II or III make it difficult to draw conclusions about indication and outcome of monosegmental grafts. To date, no large trials are available, and the medical literature has progressively relied on meta-analysis, a helpful tool that synthesizes data from multiple small studies to obtain significant conclusions.
LRD, living related donor; MLT, monosegmental liver transplantation.
Patients and Methods
A MEDLINE literature search from 1984 to September 2004 using the terms “Liver Transplantation” and “Monosegmental” or “Monosegments” limited to title or abstract with publication in the English language was conducted. The bibliographies of the recovered articles were also examined to find supplementary references of data. When articles describing the same patients were reviewed, only the one containing the most complete information was included.10–12 The data from each study were extracted and analyzed regarding donor and recipient data as follows: donor status (living or cadaveric), donor weight, donor operative details (surgical techniques used in left lateral further reduction), recipient indication for liver transplantation, age and recipient weight, graft-to-recipient weight ratio, segment utilized, recipient operative details (primary or secondary abdominal closure), and outcome (postoperative complications and survival).
Nine publications were identified from 1995 to 2004.5–13 A total number of patients from 7 publications were analyzed, because 2 publications from the same institution appeared to represent partial data from other publications by the same team.10, 11 Of the selected articles, 2 publications8, 9 reported 2 patients, while 3 articles were case reports,5, 6, 13 and 2 publications7, 12 reported 6 and 14 cases, respectively. With the exception of the graft weight and graft-to-recipient body weight ratio, the magnitude and type of information disclosed in each publication were not remarkably variable. A total of 27 pediatric patients who received a monosegment transplant were identified, median age 211 days (range, 27 to 454 days) and median weight 4.6 kg (range, 2.45 to 7.4 kg).
The donor data are listed in Table 1. Four publications described the utilization of 10 cadaveric donors, while 3 papers reported a total of 17 living donors. The technical further reduction of the left lateral segments was in the back table procedure in 4 cases (4 of 27; 15%), all of them with cadaveric donors. In 23 donors (85%), the reduction was in situ; 6 cases received from a cadaveric donor, while 17 received from a living donor. Segment III was used in 21 children (78%) and segment II in 6 (22%). When segment II was used, half were of cadaveric origin. Segment III was used in 21, 14 (66%) from living donors. The median donor weight was 51.7 kg (range, 16-103 kg) and the median donor-recipient weight ratio was 12:1 (range, 4:1-25:1). The median graft weight reported in 3 publications was 194 g (range, 145-345 g), and the graft-to-recipient body weight ratio reported in the same papers was 3.12% (range, 2.2%-5.2%).
The recipient characteristics are listed in Table 2. The reasons leading to liver transplantation were biliary atresia in 10 patients, fulminant hepatic failure in 11 (neonatal hemochromatosis in 4, hepatitis B virus-related in 2, unknown origin in 3, and not reported in 2), retransplantation in 3 (hepatic artery thrombosis in 2 and primary nonfunction in 1), and infantile hepatic hemangioendothelioma, liver cirrhosis, and biliary paucity in 1 each. In 14 patients (52%), the indication for liver replacement was medical urgency (e.g., fulminant liver failure or the need for retransplantation). The median recipient age was 211 days (range, 27-454 days). The median weight was 4.6 kg (range, 2.45-7.4 kg). The type of abdominal closure was reported in 25 of 27 patients. Primary closure was achieved in 30%. Reported surgical complication rate was 22% (pleural effusion, diaphragmatic paralysis, biliary stenosis, bile leak, hepatic artery thrombosis, portal vein thrombosis). Vascular complication was 7.4%, with 1 portal vein thrombosis and 1 hepatic artery thrombosis. In addition, there were no retransplantations, and overall patient survival was 85% after a median follow-up of 21 months.
Table 2. Recipient Characteristics, Complications, Type of Abdominal Closure, and Outcome
Reference and patient no.
Abbreviations: FHF, fulminant hepatic failure; HAT, hepatic artery thrombosis; NR, not reported; PVT, portal vein thrombosis.
In liver transplantation for small infants, the problem is large-for-size grafts, and the left lateral segment could exceed a 5% to 6% graft-to-recipient body weight ratio. When the estimated graft-to-recipient body weight ratio is more than 4% on preoperative volumetry, a further graft reduction could be necessary to overcome the large-for-size graft syndrome.14 The problems of large-for-size grafts are the insufficient blood flow to the revascularized liver and the small size of the recipient's abdominal cavity, with inadequate tissue oxygenation and graft compression.11, 12 In some small infants, the use of monosegmental liver transplantation could allow for an easier abdominal wall closure and avoid an insufficient blood supply to the graft. Avoiding the use of synthetic mesh and secondary closure can also reduce the chance of abdominal-wall infectious complications.6, 9
In the 1990s, Houssin et al.2 described a new reduction technique. Only 1 segment with the resection of segment III from the left lateral segment was used, to avoid the inability of closing the abdominal cavity. This further reduction was performed after implanting the graft, and a liver resection of a recently revascularized graft was technically complicated by hemostasis disorders. Strong et al.5 described a case in which only segment III was implanted. The reduction was at the back table from the left lateral segment of a cadaveric donor. Mentha et al.6 implanted segment II, also from a cadaveric donor, and the reduction was also performed at the back table, aided by the injection of methylene blue in the portal branch of segment III. Srinivasan et al.7 described 6 cases of segment III grafts from cadaveric donors transplanted in patients with acute liver failure, and at that time, they stated that “…this technique could also be potentially extended to living related liver transplantation.” At that time, MLT was used only in urgent conditions for fulminant hepatic failure or retransplantation.
Prior to 2000, there were no reports of MLT from an LRD. Santibañes et al.9 were the first to describe a pediatric MLT using a liver segment resected in situ from an LRD. They published 2 cases in children weighing 7 kg, using segment II. Noujain8 reported on a study of 15 patients weighing less than 5 kg using 2 MLTs from a cadaveric donor with back table reduction of segment II as a graft. Despite the few cases of segment II liver reduction, the paper from Santibañes reported 100% of biliary complications, while the paper from Noujain reported no vascular or biliary complications. The small sample of segment II liver reduction makes it difficult to draw conclusions about the rate of complications, in comparison to segment III liver reduction.
The larger single-center experience with MLT was at Kyoto University, especially with segment III, with 14 cases reported between September 2000 and November 2002 by Kasahara et al.12 They were the first to perform and to highlight the advantage of MLT with segment III in an elective setting. The Kyoto team also accented the utilization of the intraoperative ultrasonography to determine the transection plane between segment II and III. The transection line in segment III was made to preserve the entire length of the hepatic vein (Fig. 1). In another paper, they also emphasized the associated anatomical disadvantages of a large graft.14 The concept of large-for-size graft is estimated in infants whose graft-to-recipient body weight ratio is evaluated in over 4.0% by preoperative volumetry. Kiuchi et al. describe some anatomical and even immunological disadvantages of the large-for-size grafts.14 They describe a higher rate of vascular complications and more acute rejection episodes, in the first month, in recipients of large-for-size grafts. Despite these drawbacks, the negative impact of the large-for-size grafts is less pronounced in comparison to the lower survival rate of the small-for-size grafts in adults.
Our group also reported on MLT using segment III from an LRD.13 Segment II was resected in situ and discarded. This resection is not difficult and does not represent any danger to the pedicle vessels or to the left hepatic vein. The cut line was far enough from the pedicle elements that needed to be preserved, and we avoided some ischemic areas in the monosegmental graft (Fig. 2). With the help of intraoperative ultrasonography, the segment III hepatic vein could be preserved. Furthermore, with this technique the anastomosis was the same as performed when the left lateral segment from an LRD is implanted.4 Additionally, since the first case, we have performed 3 other MLTs from an LRD in small children with a median weight of 6.0 kg.
To create the segment II graft in situ, it is necessary to identify and to not injure the portal pedicle, with a hazardous dissection at the base of the umbilical fissure. Since the publication from Sirinivasan et al.,7 MLT with segment III appears to be technically easier and safer than segment II MLT. The in situ reduction at the donor operation is a safe procedure with no more than 15 to 20 additional minutes needed and with no additional blood loss. The monosegmental reduction at the back table will increase cold ischemia time. The procedure to remove segment II after the graft revascularization in the recipient could be hazardous because of coagulation disorders in the recipient of the recently reperfused graft.
Available publications of liver transplantation in small infants, especially those weighing less than 10 kg, not using MLT reported a complication rate (required reoperation) between 25 and 46%.15–20 The vascular complication and retransplantation rate in those papers seem to be higher than our findings with MLT in this meta-analysis, but the overall survival was comparable (Table 3). MLT does not avoid a secondary closure of the abdominal wall and the use of synthetic mesh. The majority of the patients (70%) were submitted to a secondary closure. It seems that the major concern of MLT is not the possibility of achieving a primary abdominal-wall closure, but rather a sufficient vascular inflow and tissue oxygenation in a graft-to-recipient body weight ratio under 4%, with lower vascular complication and graft dysfunction.
Table 3. Patient Characteristics, Complications, Retransplantation, and Survival Rates in Reported Series of Liver Transplantations in Small Infants Not Using MLT
Abbreviations: Retx, retransplantation; NR, not reported; HAT, hepatic artery thrombosis.
The MLT has been recently introduced as a routine option for elective liver transplantation in small infants, especially with segment III from a living donor. In an MLT from a living donor, monosegmentectomy seems to be as safe as standard left lateral segmentectomy, with no increased complication rate at the donor operation. It seems that MLT does not increased morbidity and mortality in small recipients. Patient survival was 85.2% (median follow-up time, 21 months), despite almost half of the patients undergoing transplantation under an urgent fashion. The survival was comparable with that of patients weighing less than 10 kg who received a transplant of grafts other than MLT (Table 3). The incidence of postoperative bleeding and bile leakage from the 2 transected surfaces was null, whereas hepatic artery and biliary complications were potentially lower without retransplantations in this meta-analysis.
The authors thank Prof. Mureo Kasahara and his colleagues from the Department of Transplant Surgery for the information provided about their experience of monosegmental liver transplantation in Kyoto University, Japan.