Short-term weight reduction (SWR) program can reduce the steatosis and convert marginal donors to low-risk donors [1]. It changed objective indices of steatosis and fibrosis using non-invasive imaging tools. Choi et al. [2] confirmed statistically significant changes in weight, fatty liver index, hepatic steatosis index, and magnetic resonance spectroscopy fat fraction after the SWR program. It could broaden the potential donor pool for living donor liver transplantation (LDLT).

LDLT prioritizes the safety of both the recipient and the donor. Safety can be evaluated from three main aspects of the liver graft or remnant liver: volume, quality of the parenchyma and vascular anatomy (especially outflow). Among them, volume issue might be the most critical issue in LDLT. Preoperatively, Graft-to-recipient weight ratio (GRWR) and percentage of remnant liver are calculated to assess recipient and donor safety, respectively. A low GRWR can result in impaired liver function, increased portal pressure, and the development of small-for-size syndrome (SFSS) [3], while a high GRWR may lead to incomplete graft inclusion in the abdominal cavity, causing large-for-size syndrome (LFSS) [4]. Therefore, appropriate graft selection (right vs. left) is made based on pre-operative volumetric data to minimize the risk of graft size related issues.

We experienced one LDLT case that SWR program of the donor reduced the volume of the liver significantly together with qualitative improvement and changed a clinical decision to switch from using the left liver to the right liver as the graft during surgery.

Demographics of Initial Visit

During the first visit to Seoul National University Hospital on October 4, 2022, the donor (blood type: B+) had no significant medical history and was generally healthy. At that time, the blood test results showed a serum total bilirubin (TB) level of 0.8 mg/dL (normal range: 0.2–1.2 mg/dL), aspartic acid transaminase (AST) level of 24 IU/L (normal range: 1–40 IU/L), and alanine aminotransferase (ALT) level of 55 IU/L (normal range: 1–40 IU/L). The blood tests also confirmed negative findings for HBsAg and anti-HCV (Table 1). Computed tomography (CT) liver transplantation donor preoperative 3D (contrast) and magnetic resonance image (MRI) liver transplantation donor preoperative (contrast) were performed. The CT scan revealed a variant where the middle hepatic artery (MHA) originated from the right hepatic artery and the presence of a right inferior hepatic vein. Severe fatty infiltration was also observed (Fig. 1A). The MRI scan showed a hepatic steatosis with a fat fraction of 15.3%. As for the recipient (blood type: A+), who was scheduled for LDLT, the medical history included four episodes of trans-arterial chemoembolization and radiation therapy in the liver segment III due to hepatocellular carcinoma related with hepatitis B virus cirrhosis. The blood test results for the recipient showed a TB level of 4.2 mg/dL, AST level of 24 IU/L, and ALT level of 19 IU/L. At the time of the visit, the donor had a height of 176 cm and a weight of 90.7 kg, resulting in a body mass index (BMI) of 29.28 kg/m2, while the recipient had a height of 155 cm and a weight of 47.3 kg, resulting in a BMI of 19.69 kg/m2 (Table 1).

Table 1 . Demographics before and after the short-term weight reduction program.

Patient	Characteristic	First visit (7 months before surgery)	After SWR (at the time of surgery)
Donor	Sex	Male
	Height (cm)	176
	Blood type	Rh+ B
	Weight (kg)	90.7	84.45
	BMI (kg/m2)	29.28	27.26
	TB/DB (mg/dL)	0.8/0.2	1.3/0.3
	ALP/GGT (IU/L)	53/46	48/21
	AST/ALT (IU/L)	24/55	18/19
	Albumin (g/dL)	4.6	4.5
	PT INR	0.96	0.96
	BUN/Cr (mg/dL)	12/0.86	26/0.77
	Na/K/Cl (mmol/L)	137/4.3/103	140/4.1/106
	Total liver volume (mL)	1660	1256
	Rt. Liver volume (mL)	1134	849
	Rt. GRWR (%)	2.40	1.65
	Lt. Liver volume (mL)	526	407
	Lt. GRWR (%)	1.11	0.79
Recipient	Sex	Female
	Height (cm)	155
	Blood type	Rh+ A
	Weight (kg)	47.3	51.4
	BMI (kg/m2)	19.69	20.99
	TB/DB (mg/dL)	4.2/1.6	2.0/0.6
	ALP/GGT (IU/L)	73/49	52/54
	AST/ALT (IU/L)	24/19	28/17
	Albumin (g/dL)	2.5	3.4
	PT INR	1.64	1.20
	BUN/Cr (mg/dL)	7/0.65	26/0.81
	Na/K/Cl (mmol/L)	136/5.1/104	140/3/98

BMI, body mass index; TB, total bilirubin; DB, direct bilirubin; ALP, alkaline phosphatase; GGT, gamma-glutamyl transferase; AST, aspartate aminotransferase; ALT, alanine aminotransferase; PT INR, prothrombin time international normalized ratio; BUN, blood urea nitrogen; Cr, creatinine; Na, sodium; K, potassium; Cl, chloride; Rt., right; Lt., left; GRWR, graft-to-recipient weight ratio..

Figure 1. Pre-contrast CT image before (A) and after (B) the short-term weight reduction program. Constrat CT image before (C) and after (D) the short-term weight reduction program.

An analysis of the anatomical, qualitative, and volumetric aspects of the graft was conducted. Volumetric analysis was performed using a program called Dr. Liver®. The total liver volume was measured as 1,660 mL, with 1,134 mL for the right liver and 526 mL for the left liver (Fig. 2A). The GRWR for the recipient's weight of 47.3 kg was calculated as 2.40% for the right liver and 1.11% for the left liver. The left liver was decided to be used considering volume. However, if the left liver were used as the graft, dual anastomosis (left hepatic artery and MHA) would be required during LDLT, which could increase the likelihood of postoperative vascular complications. Qualitatively, the presence of fatty liver raised concerns about the graft's proper function in both the donor and the recipient after LDLT. To address this, a SWR program was planned to promote the recovery of the fatty liver.

Figure 2. Volumetry done by a program called Dr. Liver® before (A) and after (B) the short-term weight reduction program. LV, liver volume; PV, portal vein; HV, hepatic vein; TFLV, total functional liver volume; RLV, right liver volume; RGW, right graft weight; LLV, left liver volume.

After the SWR Program (Table 1)

Due to the difficulties associated with using the left liver as the graft, including high fat content, the donor underwent the SWR program (from October 4, 2022, to May 11, 2023, approximately 31 weeks). Along with blood tests, CT Liver TPL Donor Preop 3D (contrast) was performed. The blood test results showed a TB level of 1.3 mg/dL, with AST and ALT levels of 18 IU/L and 19 IU/L, respectively. No abnormalities were observed in other liver function tests, and indicators of kidney function, such as glomerular filtration rate, creatinine, and blood urea nitrogen, were within the normal range. After the SWR program, the donor’s height was measured as 176 cm, and weight was 84.45 kg, resulting in a BMI of 27.26 kg/m2. A total weight loss of 6.25 kg was observed compared to before the program. The recipient had a TB level of 2.0 mg/dL, with AST and ALT levels of 28 IU/L and 17 IU/L, respectively, during the same period of blood testing. The prothrombin time international normalized ratio was within the normal range at 1.20, and no significant abnormalities were noted in other blood test results, except for a decrease in blood cell count and a low potassium level. The recipient’s weight increased to 51.4 kg, resulting in a BMI of 20.99 kg/m2 (Table 1).

When comparing the results before and after the SWR program, changes in the region of image values were observed in the CT scan, indicating changes in steatosis (Fig. 1B). Using the Dr. Liver® program, liver volume measurements were taken, showing a total liver volume of 1,256 mL, with 849 mL for the right liver and 407 mL for the left liver (Fig. 2B). The GRWR for the recipient's weight of 51.4 kg was calculated as 1.65% for the right liver and 0.79% for the left liver. Based on these findings, it was confirmed that the right liver could also be considered as a graft option, contrary to the initial decision of using the left liver based on volumetric considerations. Considering the anatomical perspective and the ease of transplantation, the right liver was ultimately selected as the graft.

After Living Donor Liver Transplantation

Following the final plan, a laparoscopic living donor hepatectomy was performed on May 12, 2023, with the right liver selected as the graft. The weight of the graft was measured as 836 g. The volumetric measurement of the right liver using Dr. Liver® was approximately 849 mL, corresponding to a weight of around 849 g, showing only a slight difference of 13 g compared to the actual measurement. Calculating the GRWR for the recipient's weight of 51.4 kg resulted in 1.62%, indicating that the graft could be placed within the recipient's abdominal cavity without difficulty during LDLT. The surgery concluded without any acute complications after vascular and biliary anastomosis, and no issues were found regarding blood flow through the anastomosed vessels.

The donor received conservative treatment in a general ward and discharged without any complications at postoperative day 5. TB levels increased to 3.8 mg/dL one day after surgery and continued to rise to 4.4 mg/dL and 5.2 mg/dL on the second and third days after surgery, respectively. However, TB levels decreased to 2.8 mg/dL on the fourth day after surgery and remained stable at 2.9 mg/dL on the fifth day after surgery. AST and ALT levels also increased to 134 IU/L and 154 IU/L, respectively, until the second day after surgery but showed a declining trend afterward, reaching 78 IU/L and 137 IU/L on the fifth day after surgery.

The recipient underwent postoperative observation in the intensive care unit for three days and was then transferred to a general ward without acute complications. TB levels worsened to 11.0 mg/dL on the fourth day after surgery but decreased to 2.6 mg/dL on the fourteenth day after surgery at the time of discharge. Similarly, AST and ALT levels increased to 69 IU/L and 220 IU/L, respectively, until the second day after surgery but gradually improved, with levels within the normal range (11 IU/L and 23 IU/L) at the time of discharge.

Previous studies have shown that changes in the weight of potential donors can lead to qualitative changes in grafts and expand the potential donor pool. In particular, for cases with hepatic steatosis, weight loss can reduce hepatic steatosis observed in imaging tests and improve the quality of the liver, allowing individuals previously excluded as potential donors to be reconsidered [2]. The decrease in body weight of potential donors results in a reduction of fat infiltration into the liver, leading to an overall decrease in hepatic volume. Consequently, this expands the potential donor pool. Previous studies have demonstrated successful cases where potential donors were selected with increased weight to prevent SFSS during LDLT [5]. In this case, it was observed that changes in the donor's weight through the SWR program could lead to changes in the overall liver volume, allowing for the selection of a different graft that had initially been excluded due to volumetric considerations, thereby altering clinical decisions related to the surgery.

When selecting potential donors for LDLT, it is common practice to prioritize imaging tests in addition to basic information including past medical history. This is to screen potential donors based on imaging findings as the remnant liver volume after LDLT can affect the postoperative liver function in the donor, and the occurrence of SFSS and LFSS in the recipient can lead to liver failure. Therefore, imaging tests are primarily used to select potential donors. Once potential donors are identified through imaging tests, further evaluations are conducted to assess their suitability before proceeding with LDLT. However, there can be a time difference between the imaging tests and the actual LDLT, and the condition of potential donors at the time of imaging tests and at the time of LDLT can vary. Therefore, it is crucial to consider the possibility of differences in weight and the degree of hepatic steatosis, which can affect the qualitative and volumetric aspects of the graft. In cases where potential donors exhibit severe hepatic steatosis, additional imaging tests performed just before surgery to reassess the qualitative and volumetric aspects of the graft would be advisable.

There was no funding related to this study.

All authors have no conflicts of interest to declare.

Conceptualization: KWL. Data curation: YK. Formal analysis: YK. Investigation: YK. Methodology: All. Resources: KWL, YRC, SYH, NJY, SKH, JML, KSS. Supervision: KWL. Visualization: YK. Writing – original draft: YK. Writing – review & editing: YK, KWL.