Donor Hemosiderosis Does Not Affect Liver Function and Regeneration in the Setting of Living Donor Liver Transplantation

Authors


Abstract

Living donor liver transplantation (LDLT) demands a careful assessment of abnormal findings discovered during the evaluation process to determine if there will be any potential risks to the donor or recipient. Varying degrees of elevated hepatic iron levels are not uncommonly seen in otherwise healthy individuals. We questioned whether mild expression of hemosiderin deposition presents a safety concern when considering outcomes of living donation for both the donor and the recipient. We report on three LDLT patients who were found to have low- to moderate-grade hemosiderin deposition on liver biopsy. All other aspects of their evaluation proved satisfactory, and the decision was made to proceed with donation. There were no significant complications in the donors, and all demonstrated complete normalization of liver function postoperatively, with appropriate parenchymal regeneration. The recipients also had unremarkable postoperative recovery. We conclude that these individuals can be considered as potential donors after careful evaluation.

Abbreviations
HCC

hepatocellular carcinoma

HFE

hereditary hemochromatosis

LDLT

living donor liver transplantation

LIC

liver iron concentration

ROS

reactive oxygen species

TLV

total liver volume

Introduction

Adult-to-adult living donor liver transplantation (LDLT) is one method that has been used to minimize time spent awaiting deceased donor liver transplantation and to reduce deaths on the waitlist. In an effort to maximize donor safety while preventing unnecessary limitations to potential live donors, it is important to delineate whether specific abnormalities should be acceptable and safe when considering donor and recipient posttransplant liver function and regeneration [1]. Systemic and localized liver iron overload can arise from heterogeneous mutations of iron metabolism genes, or as part of acquired disorders in which excessive iron is preferentially accumulated in liver parenchymal and nonparenchymal cells. Low-grade iron overload may be seen in common chronic liver diseases, including viral hepatitis, alcoholic liver disease, nonalcoholic fatty liver disease and hepatocellular carcinoma [2-4].

The main concern with iron overload in hereditary or acquired disorders is the development of sideronecrosis and the consequent mild chronic inflammation that, in the advanced stage, proceeds to the development of fibrosis. This phenomenon may be more significant in the setting of chronic liver disease, where hemosiderosis was demonstrated to be associated with liver dysfunction [5]. The significance of iron overload in the healthy individual is yet to be determined. In the living donor liver transplant setting the presence of iron in a donor liver biopsy was associated with mild sinusoidal fibrosis, and has been speculated to be associated with the development of steatohepatitis [6].

The effect of intrahepatocellular hemosiderin on hepatic regeneration is unclear. Limited data from animal models have demonstrated that regenerating rat livers have a substantially greater degree of iron uptake [7]. This evidence suggests that proliferating hepatocytes have a large requirement for iron; however, there have been no studies in humans demonstrating the potential effects of increased levels of preexisting intrahepatic iron on hepatic regeneration. The experience in this animal model provided supporting evidence to proceed with living donation from these individuals. In this report, we document uneventful recovery, intact hepatic regeneration and normal return of liver synthetic function in the donors and recipients of livers with elevated iron stores.

Cases and Outcomes

The performance of this work was approved by the Institutional Review Board on Human Subject Research at the Hospital of the University of Pennsylvania. The three donors were evaluated during a period in our center when all donors obtained a preoperative liver biopsy. After careful evaluation and discussion, three donors all underwent uneventful right lobe liver resection. All three right lobes were transplanted into recipients with decompensated hepatitis C cirrhosis, none of whom who had any findings suggesting hemochromatosis.

Donor 1

A 23-year-old Caucasian male was evaluated for potential LDLT to his father. He was healthy with no history of regular medication or nutritional supplement intake. The donor had remote history of alcohol intake of up to 12 ounces of beer a day, and only sporadic intake in the 2 years prior to evaluation. On examination, his BMI was 23.6, with no abnormal clinical findings. His laboratory studies revealed normal liver function studies. The MRI subtraction image showed the presence of small amounts of iron, and the preoperative liver biopsy showed grade 2 intrahepatocellular hemosiderin deposition. Results of iron studies were normal, and testing for C282Y and H63D mutations was negative (Table 1). Volumetric imaging revealed liver volumes that were appropriate for donation (Table 2). The decision was made to proceed with donation. He underwent a right hepatic lobectomy, with the right lobe graft measuring 1097 g, and a calculated 33% of his liver remaining. A postoperative MRI 13 weeks after donation demonstrated significant left lobe growth with a total volume of 1120 cm3 (volume reconstitution = 68.7% of starting total liver volume [TLV]).

Table 1. Donor demographics, laboratory data and genetics
 Donor 1Donor 2Donor 3
Age at donation233526
GenderMaleMaleFemale
RaceCaucasianCaucasianCaucasian
Transferrin saturation (%)283824
Serum transferrin (mg/dL)279300210
Serum ferritin (ng/mL)150200102
Serum iron (µg/dL)11122371
Hemosiderosis grade211
C282Y mutationNegativeNegativeHeterozygous
H63D mutationNegativeNegativeHeterozygous
Table 2. Donor pre- and posttransplant hepatic volumetric outcomes
 Donor 1Donor 2Donor 3
  1. TLV, total liver volume.
Preoperative data
Pre-TLV (cm3)163017741155
Volume of resected lobe (g)10971140690
Volume of remnant left lobe (cm3)533627465
Remnant remaining (% of TLV)333640
Postoperative data
Imaging weeks postdonation13913
Post-TLV on follow-up imaging (cm3)112014201168
Absolute growth (cm3)587793703
Volume reconstitution (%)6980101
Volume increase (% of TLV)210224251

Donor 2

A 35-year-old Caucasian male was evaluated for potential LDLT to his mother. He had no known medical problems and consumed alcohol occasionally. On examination, his BMI was 28.8 and no abnormal clinical findings were seen. His laboratory studies revealed normal liver function studies. Mild iron deposition could be detected on the MRI as subtle signal loss on the in-phase t1-weighted images when compared to the corresponding opposed phase image. A liver biopsy showed grade 1 mild intrahepatocellular hemosiderin deposition. Results of iron studies were normal, and testing for C282Y and H63D mutations was negative (Table 1). Volumetric imaging showed liver volumes that were appropriate for donation (Table 2). He underwent a right lobectomy, with the right lobe weighing 1140 g, and a calculated 36% of his liver remaining. His postoperative course was uneventful. His 8-week MRI showed interval hypertrophy of the left lobe with the total left lobe volume estimated to be 1420 cm3 (volume reconstitution = 80.0%).

Donor 3

A 26-year-old Caucasian female was evaluated for potential LDLT to her mother. She had a medical history of irritable bowel syndrome and migraines, neither of which were considered as a contraindication for donation. She drank alcohol only occasionally. Physical examination was normal, and her BMI was 21.3. Her laboratory studies revealed normal liver function (Table 1), and MRI showed liver volumes were appropriate for donation (Table 2). Mild iron deposition could be detected on the MRI as subtle signal loss on the in-phase t1-weighted images when compared to the corresponding opposed phase image. A liver biopsy showed grade 1 mild intrahepatocellular hemosiderin deposition. Results of iron studies were normal, and testing for C282Y and H63D mutations was heterozygous. She underwent a right lobectomy, with the right lobe measuring 690 g, and 40% of her liver remaining. Her postoperative course was also uneventful. Her 12-week MRI showed left lobe hypertrophy with a calculated left lobe volume of 1168 cm3 (volume reconstitution = 101.1%).

Histologic review of donor liver biopsies

The iron staining on the liver biopsies demonstrated diffuse intrahepatocellular iron that was either limited to hepatocytes in the immediate periportal area (grade 1—donors 2 and 3), or extending to zone 1 (grade 2—donor 1). There was no Kupffer cell hyperplasia. Grade 2 siderosis was associated with minimal chronic inflammation.

Recipients

None of the recipients experienced small-for-size syndrome, early allograft dysfunction or rejection. At 3 months postdonation they exhibited normal liver synthetic function. In all cases serum iron was normal at 3 months. Liver volumetric studies demonstrated acceptable regeneration capacity (Table 3). Liver function tests at 1 year were within normal limits.

Table 3. Posttransplant recipient volumetric outcomes
 Recipient 1Recipient 2Recipient 3
Starting donated liver volume (g)10971147690
Imaging weeks posttransplant13813
Liver volume in follow-up imaging (cm3)210513041377
Absolute growth (cm3)1008157687
Volume increase (%)192114200

Discussion

Iron is a crucially important element in normal cellular function, and thus the regulation of iron homeostasis is tightly controlled. When this regulation is disrupted, as in hereditary hemochromatosis (HFE), abnormal intestinal absorption of iron leads to cellular toxicity, tissue injury and fibrosis via the deposition of iron in parenchymal cells of the heart, pancreas and liver. Iron-generated oxyradicals contribute to the peroxidation of lipid membranes, leading to organelle fragility and cellular toxicity [8-10]. This process is thought to contribute to hepatocellular necrosis and/or apoptosis in the liver with the subsequent activation of hepatic stellate cells and the development of hepatic fibrosis and cirrhosis.

The pathology of iron deposition in the setting of hereditary or transfusion-related hemosiderosis is well described [11]. Scheuer [12] proposed a grading system for liver siderosis in which grade 1 is minimal, grades 2 and 3 are intermediate and grade 4 is massive. It is important to recognize that iron deposition in these settings is always abnormal since this grading is described for individuals with hereditary or acquired liver disorders, guiding treatment of the primary disorder in order to reduce iron overload. The significance of any iron deposition at any grade in an otherwise healthy individual is not known.

There are no descriptions in the literature regarding the impact of mild hemosiderosis on liver function, fibrosis and/or regeneration in humans after liver resection for transplantation of reduced-size allografts. The only data available are animal studies in which high intrahepatic iron storage may have been an advantage in the short term, since regenerating rat livers require high degrees of iron intake [7]. The three donors described above had relatively mild hepatic hemosiderosis. Two donors tested negative for the HFE mutation, making HFE less likely, but not completely impossible, as the genetic mutation is identifiable in approximately 80–85% of those with the classic phenotype [13, 14]. The third donor was a compound heterozygote for the mutation. Since none were found to be homozygous for the HFE mutations, we decided to proceed with donation and transplantation. The results of the first case made us more confident when the other cases were assessed. Ultimately, these donors fared well, as did the recipients.

At first glance, this case report series appears to be a trivial description of outcomes after donation for a mild abnormality that should otherwise be of no consequence to a healthy individual. All the donors were completely healthy, and the findings were incidental and discovered in the setting of either mildly out of range laboratory tests, a minor MRI finding, or at a time when biopsies were routinely done as part of the evaluation at our center. Despite the benign nature of these findings in healthy individuals, they were debated when these patients were evaluated and discussed at our donor patient selection meeting. We performed further genetic testing and eventually decided to proceed with donation on all three. The importance of this three-case experience is that it documents that mild hemosiderosis does not appear to impact immediate and long-term postdonation liver function and regeneration.

Liver biopsy is considered the standard for assessment of liver iron concentration (LIC); however, the procedure is invasive and is associated with sampling error. The use of MRI to estimate hepatic iron became a practical reality since comparative studies demonstrated excellent correlation with LIC. Recently, liver iron estimate by MRI became the primary outcome measurement for staging as well as assessing efficacy of chelating therapy [15-17]. We began our LDLT program by performing liver biopsies on all donors before proceeding to the operative room in order to minimize the possibility of unexpected findings at laparotomy. While we no longer perform liver biopsy as a standard part of the living donor evaluation of all donors, we now use MRI to assess liver iron content [16].

Previous description of similar findings in living donor candidates [6] and our own cases described above led us to propose a decision algorithm which makes donor safety a priority while not eliminating potential appropriate donors (Figure 1). Careful determination of ferritin levels and consideration of MRI findings may indicate the need for genetic testing to rule out hereditary etiologies which should be a contraindication for donation. A liver biopsy demonstrating hemosiderosis grade 3 or higher should also be considered an exclusion criteria. Since mild to moderate alcohol consumption has been shown to increase the prevalence of iron overload, it is reasonable to ask the donor candidate to stop drinking even when found to have mild hemosiderosis.

Figure 1.

Algorithm for living donor evaluation.

We emphasize that any abnormality found during a donor evaluation requires careful assessment in order to ensure donor safety, and the benefit to the recipient must always be weighed against the risk to the donor, no matter how minimal [18]. Importantly, we would not restrict living donation for individuals with mild to moderate hemosiderosis based upon our findings that, in this particular setting, there were no significant adverse events documented during or after donation, regeneration was adequate, and donor liver synthetic function returned to normal limits.

Disclosure

The authors of this manuscript have no conflicts of interest to disclose as described by the American Journal of Transplantation.

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