In liver transplantation (LT) for small infants, graft size matching to the recipient’s abdomen is the most important factor because implantation of a large-for-size graft hinders primary closure of the abdomen and can induce various vascular complications [1,2]. To make a left lateral segment (LLS) graft as small as possible, a LLS graft can be reduced to a segment II (S2) or III (S3) monosegment or hyperreduced LLS graft [1-9]. For very small infants weighing around 3 kilograms (kg), such a monosegment or hyperreduced LLS graft can be very large for abdominal implantation. Thus, there is an urgent need to create a hyperreduced monosegment graft through thorough assessment of the donor LLS anatomy. We herein present the surgical technique and clinical outcome of pediatric living donor liver transplantation (LDLT) using a hyperreduced S2 monosegment (HRS2MS) graft in an infant weighing 3 kg.

A female infant was born through cesarean section at a gestational age of 28 weeks 5 days due to oligohydramnios and failure of growth for more than one week. Her birth weight was 1,030 g. This patient with multiple congenital anomalies was cared at the neonate intensive care unit.

At three months after birth, neonatal cholestasis developed with gradual rise in total bilirubin and liver enzymes. A magnetic resonance imaging study showed hepatosplenomegaly (Fig. 1). Percutaneous liver biopsy showed neonatal giant cell hepatitis.

Figure 1. Pretransplant magnetic resonance imaging findings at three months after birth showing hepatomegaly (A), normal intrahepatic vasculature (B), and hepatosplenomegaly with mild ascites (C).

At four months after birth, progression of liver failure continued with deterioration of the general condition and vital signs. Thus, we decided to perform urgent LDLT at the patient body weight of 3.0 kg with marked hepatosplenomegaly and ascites (Fig. 2). Considering that her height was 49 cm at actual two months after calculation of the gestational age of 28 weeks 5 days and 10 weeks at the neonatal intensive care, her ideal body weight was estimated to be only 2.1 kg. It was not possible to wait further for patient growth because of rapid deterioration of liver function.

Figure 2. Perioperative computed tomography (CT) findings of the donor liver. The preoperative left lateral segment volume was estimated to be 292 mL (A) and the maximal anterior-posterior diameter was 5 cm (B). CT scans taken at 7 days (C) and one month (D) after donation showed uneventful recovery of the remnant donor liver.

The living donor was a 33-year-old mother of the patient. Her LLS volume was estimated to be 292 mL (Fig. 3A, B). For graft-recipient size matching, we planned to perform procurement of a HRS2MS graft by making the size of the liver graft as small as possible.

Figure 3. Pretransplant computed tomography findings at transplantation showing marked hepatomegaly (A), massive ascites (B), and marked hepatosplenomegaly (C).

We measured the size of the LLS liver and marked the surface along the falciform ligament to split the usual LLS graft, and then made additional markings at the lateral part of segment II and ventral part of segment III. After identification of the running course of the left hepatic vein course using intraoperative Doppler ultrasonography, the lateral aspect of the LLS liver was resected while preserving the medial branch of the left hepatic vein. Glissonean pedicles of the S2 and S3 to the left of the umbilical fissure were identified and the distal pedicle of S3 was ligated. The plane of resection of S3 was determined by a demarcation line along the inferior aspect of the S2. Finally, the ventral part of segment III and the lateral part of segment II were removed (Fig. 4).

Figure 4. Recovery of the hyperreduced S2 monosegment (HRS2MS) segment graft (A, B). The size of the left lateral segment was measured (C, D). The lines for hepatic transection were marked at the surface of the donor liver (E). Intrahepatic vascular anatomy was depicted (F–H). Liver splitting and size reduction were performed (I). Hilar vascular structures were isolated (J–L). The size of the HRS2MS segment graft was measured at the back table.

We performed recipient hepatectomy according to the standard procedure for pediatric LDLT. The liver was enlarged with abundant ascites. The recipient’s native portal vein appeared normal (Fig. 5A, B).

Figure 5. Recipient hepatectomy and graft implantation (A, B). Recipient hepatectomy was performed (C, D). The three hepatic vein orifices of the recipient’s inferior vena cava were opened to make a large orifice, which was well matched in size with the graft hepatic vein (E, F). The branch patch of the recipient’s portal vein was used for portal vein reconstruction (G). One left hepatic artery was reconstructed under surgical microscopy (H). Roux-en-Y hepaticojejunostomy was performed for biliary reconstruction.

At the back table, the weight of this HRS2MS graft was 123 g, which was a graft-to-recipient weight ratio (GRWR) of 4.1%. The orifice of the graft left hepatic vein appeared to be large enough; thus, we did not perform any venoplasty procedure (Fig. 6A–C).

Figure 6. Graft preparation at the back table. Graft size (A), graft outflow vein diameter (B) and graft portal vein diameter (C) were assessed. The size of the implanted liver graft was compared with the size of the surgeon’s hand (D).

After performing native liver removal, we opened the three hepatic vein orifices of the recipient’s inferior vena cava to make a large orifice, which was well matched in size with the graft hepatic vein (Fig. 5C, D). We used the branch patch of the recipient’s portal vein for portal vein reconstruction (Fig. 5E, F). One left hepatic artery was reconstructed under surgical microscopy (Fig. 5G). We performed Roux-en-Y hepaticojejunostomy for biliary reconstruction (Fig. 5H).

The recipient’s native liver was enlarged and weighed 336 g, and there was massive ascites. The abdomen was distended to accommodate this HRS2MS graft, permitting primary closure of the abdomen. The explant liver pathology showed marked hepatic necrosis with marked cholestasis and mild hemosiderosis, supporting neonatal giant cell hepatitis (Fig. 7).

Figure 7. Gross photograph of the explanted liver.

A computed tomography scan taken four days (Fig. 8) and 3 months (Fig. 9) after transplantation showed uneventful vascular reconstruction. Currently, she has been doing well for more than three months after transplantation. The donor also recovered uneventfully (Fig. 3C, D).

Figure 8. Computed tomography scan taken four days after transplantation. The abdominal wall was primarily repaired with uneventful vascular reconstruction (A, B). Ileus and splenomegaly were identified (C).

Figure 9. Computed tomography scan taken three months after transplantation. The graft liver was remodeled according to the abdominal cavity with uneventful vascular reconstruction (A, B). Mild ascites and persistent splenomegaly were identified (C).

Accumulating experience with LT for small infants is being gathered worldwide [1-11], but it is still regarded as challenging because large-for-size graft-related problems are big hurdles for successful LT, especially in very small infants. The critical issues in implantation of large-for-size grafts are the risk of abdominal compartment syndrome caused by the recipient’s small abdominal cavity, size discrepancies in vessel size, and insufficient portal circulation and tissue oxygenation [1,12-15]. To solve such critical issues, it is essential to reduce the size of liver grafts as much as possible.

The target size in graft size reduction is to make the estimated GRWR less than 4% for LT in infants [9]. An S2 or S3 monosegment graft would be ideal for making a very small liver graft with effective reduction in graft thickness. It is essential to assess the donor liver anatomy thoroughly to create a monosegment graft. The shape of a donor’s LLS liver is important for size reduction because reduction in the graft thickness is a difficult procedure [1]. The graft shape was evaluated using the graft thickness-to-anteroposterior diameter in the recipient’s abdominal cavity ratio [16]. If this ratio of thickness exceeds 1.0, primary abdominal wall closure can induce excessive graft compression and abdominal compartment syndrome; thus, so closure with a prosthetic mesh should be considered. To help reduce the graft thickness, the modified technique of a reduced-thickness LLS graft has also been reported [9]. In the present case, because of exceptional abdominal distension from hepatosplenomegaly and ascites, the latitude for graft thickness was markedly expanded, permitting primary abdominal wall closure. In our previous cases, all small infant recipients required staged abdominal wall repair through mesh coverage [10,11].

To the best of our knowledge, the present case is one of the smallest LT recipients in the world. Considering premature delivery by more than two months and growth retardation, the height of the patient was less than 1 percentile, suggesting an ideal body weight of 2.1 kg. If abdominal distension from hepatosplenomegaly and ascites was not present, LDLT operation for such a small infant would have been much difficult.

In conclusion, pediatric LDLT using a HRS2MS graft can be a useful option for treating a very small infant although large-for-size graft-related issues still remain to be solved.

There was no funding related to this study.

All authors have no conflicts of interest to declare.

Conceptualization: JMN, GCP, SH, KMK, SHO. Data curation: GCP, SH. Investigation: JMN, SH. Methodology: All. Supervision: SH. Visualization: SH, SHK, S Ha. Writing - original draft: All. Writing - review &editing: JMN, GCP, SH.