Radiographic features of potential donor livers that precluded donation.

Gastrointestinal Imaging • Original Research Hahn et al. Radiographic Features of Potential Donor Livers

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Gastrointestinal Imaging Original Research

Radiographic Features of Potential Donor Livers That Precluded Donation Lewis D. Hahn1 Sukru H. Emre2 Gary M. Israel1,2 Hahn LD, Emre SH, Israel GM

OBJECTIVE. The objective of our study was to catalog the anatomic features shown on preoperative CT that precluded living-donor liver donation. MATERIALS AND METHODS. We retrospectively reviewed the records of 159 consecutive candidates who were evaluated for potential right or left lobe liver donation from November 2007 to January 2012 using MDCT angiography and cholangiography. For the potential donors who were excluded secondary to findings depicted on preoperative imaging, we determined which findings precluded donation. RESULTS. In two (1%) patients who had no prohibitive preoperative imaging findings, anatomic abnormalities were detected intraoperatively that precluded transplantation. Sixtyone (38%) candidates were excluded from liver donation on the basis of imaging findings. Of these patients, 40 (66%) had inadequate liver volume, 14 (23%) had vascular or biliary variants, five (8%) had steatosis, and two (3%) were found to have renal cell carcinoma. Arterial and biliary variants were the most common reason for exclusion based on anatomic findings. CONCLUSION. Inadequate liver volume was the most common reason for exclusion based on preoperative imaging. Arterial and biliary anatomic variants precluded both right and left lobe transplantation in a number of cases.

I

Keywords: CT, liver, transplantation DOI:10.2214/AJR.13.10677 Received January 31, 2013; accepted after revision August 2, 2013. 1 Department of Radiology, Yale University School of Medicine, 333 Cedar St, New Haven, CT 06520-8042. Address correspondence to G. M. Israel ([email protected]). 2 Department of Surgery, Yale University School of Medicine, New Haven, CT.

WEB This is a web exclusive article. AJR 2014; 202:W343–W348 0361–803X/14/2024–W343 © American Roentgen Ray Society

maging of potential donor livers is an integral step of the evaluation for potential living-donor liver transplantation. Imaging can be performed using CT or MRI, and the examination encompasses calculation of liver lobe volumes and evaluation of vascular and biliary anatomy. The former is used to determine whether transplant can occur on the basis of adequate graft and remnant liver volumes. The latter is essential to preoperative planning; in some cases, the risks that variant anatomy pre sent may also preclude transplantation because of the risk of intra- and postoperative complications in both the donor and recipient [1, 2]. Although there are many studies in the literature about anatomic variants and the potential influence on surgical technique that they may have [3, 4], reports are variable on the specific findings that preclude liver transplantation [5–8]. Furthermore, the radiographic features that have precluded transplantation are only sparsely cataloged [9, 10]. Here, we report our experience with 159 consecutive potential liver donors and the features found at imaging that precluded liver transplantation.

Materials and Methods Institutional review board approval was obtained for this retrospective HIPAA-compliant study; written informed consent was waived. Between November 2007 and January 2012, 159 consecutive patients were evaluated as a potential liver donor for an adult patient (excludes left lateral segment donation for a child) using CT angiography and CT cholangiography. At our institution, potential donors should generally have a body mass index (BMI) of less than 32. If BMI is greater than or equal to 32, patients are cautiously evaluated and encouraged to lose weight to meet our BMI criterion before imaging. Of these 159 patients, 35 donated a portion of their liver and three were approved for donation and await surgery. The remaining 121 patients did not undergo liver donation for the following reasons: recipient died (n = 13), recipient too sick for transplant (n = 2), donor withdrew (n = 12), cadaveric donor graft used (n = 7), different liver donor used for transplant (n = 2), donor medically unsuitable (n = 22), unsuspected anatomic anomaly found during liver donation surgery (n = 2), and findings depicted on CT (n = 61). The 61 patients with findings on CT that resulted in donor exclusion constitute the cohort of this study. The patient cohort con-

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Graft−Recipient Weight Ratio (%)


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0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 20

25

30

35

40

Remnant Liver Volume (%)

Fig. 1—Axial contrast-enhanced 5-mm-thick CT image of 25-year-old man shows example of manually drawn region of interest around right lobe of liver. Right side of middle hepatic vein (arrow) was used as dividing line between right and left lobes. Surface area of right lobe on this image is 91.5 cm2 (labeled “A”), which corresponds to liver volume of 45.8 cm3 (91.5 cm2 multiplied by 0.5-cm slice thickness). P = perimeter, M = mean CT attenuation.

Fig. 2—Graph shows graft–recipient weight ratio and percentage remnant liver volume for donor liver candidates who were excluded on basis of inadequate liver volume.

sisted of 32 men and 29 women (average age, 40 years; SD, 10 years). Their medical records and CT scans were reviewed to determine the reason for exclusion. The medical chart analysis was performed by the authors, the transplant coordinator, and a transplant surgeon. In almost all cases, the cause for transplant ineligibility was determined at the interdisciplinary conference. In rare cases, this assessment was performed by the transplant surgeon before the conference (i.e., two patients with renal cell carcinoma). During this conference, the reason for ineligibility was documented. However, if the reason was not clear on retrospective review, the case was reviewed a second time by the transplant surgeon to determine the reason for ineligibility.

120 kVp (unenhanced) and 80 kVp (contrast-enhanced); and noise index, 22. The data were reconstructed to a slice thickness of 5 mm (unenhanced) and 0.625 and 5 mm (contrast-enhanced) using a standard algorithm. After CT angiography, patients received 20 mL of 52% iodipamide meglumine (Cholografin, Bracco Diagnostics) over 30 minutes. Approximately 15 minutes after the infusion was complete, CT cholangiography was performed using a slice thickness of 0.625 mm, a reconstruction interval of 0.625 mm, a pitch of 0.98, 80–120 kVp, and a noise index of 22. All patients received 25 mg of oral diphenhydramine (Benadryl, Pfizer) approximately 1 hour before the Cholografin.

MDCT Technique

Image Interpretation

CT scans were acquired using a 64-MDCT unit (LightSpeed VCT or Discovery CT750 HD, GE Healthcare). Initially patients underwent unenhanced CT, which was followed by IV contrast-enhanced MDCT angiography. Imaging was performed from the dome of the liver to the iliac crests. After unenhanced imaging, 150 mL of iohexol (Omnipaque 350, Nycomed Amersham) was administered at a rate of 4–5 mL/s. No oral contrast material was administered. The scanning delay from the arterial phase was determined using bolus-tracking software (SmartPrep, GE Healthcare), and portal venous phase images were acquired using a fixed scanning delay of 65 seconds after the start of injection. The CT parameters were as follows: slice thickness, 0.625 mm; reconstruction interval, 0.625 mm; pitch, 0.98;

The CT scans were interpreted on the clinical service by one of five radiologists with subspecialty training in abdominal imaging and were also reviewed in a multidisciplinary conference with the liver transplant team. Each examination was interpreted for liver volumes (total volume, right lobe volume, combined left lobe and caudate volumes), hepatic arterial anatomy, hepatic portal venous anatomy, hepatic venous anatomy, hepatic biliary anatomy, presence or absence of hepatic steatosis, presence or absence of liver masses, and other incidental findings not related to the liver. The total and right lobe liver volumes were determined by manually drawing regions of interest around the liver and right lobe, respectively, on 5-mm-thick images and multiplying each measurement by the slice thickness (Fig. 1). These values

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were then summed to give the total and right lobe liver volumes. The rightward side of the middle hepatic vein was used as the dividing line between the left and right lobes. The combined left lobe and caudate volumes were acquired by subtracting the right lobe volume from the total liver volume. The calculations of liver volumes were performed by the interpreting radiologist at the time of dictation on our PACS (Synapse, Fuji Systems). With respect to the donor liver volumes, the transplant team at our institution requires that the graft– recipient weight ratio be at least 0.6% and that the remnant liver volume in the donor (after removal of the intended lobe of the donor liver) be at least 33% of the total liver volume. If these criteria were not met, the potential donor was excluded from donation secondary to insufficient liver volume. For potential donors who had sufficient liver volume, the imaging studies were rereviewed by a single radiologist who characterized the hepatic arterial anatomy into one of the 10 types of the standard classification system of Michels [11]; we also added an 11th category to include other variants not described previously (Table 1). The portal and hepatic venous anatomy, biliary anatomy, and other pertinent incidental non–liver-related findings were also recorded from the clinical radiology report (Table 2). The only anatomic variant that is an absolute contraindication to donation at our institution is intrahepatic bifurcation of the portal vein. Hepatic steatosis was defined as the liver measuring less than 40 HU on unenhanced CT or the liver measuring 10 HU or less than the spleen on unenhanced CT [12, 13].

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Radiographic Features of Potential Donor Livers Results There were no complications from imaging; in particular, there were no contrast material allergy reactions. In two patients who were to undergo right lobe donation, abnormalities that were not detected preoperatively precluded transplantation intraoperatively. The first ab-

normality was an aberrant left bile duct draining into the right bile duct. The second abnormality was that the majority of blood supply supplying segment IV came from the right hepatic artery and the right portal vein. In this case, blood supply to segment IV was identified preoperatively arising from the left hepatic artery. When the

test clamp was performed (i.e., clamping both the right hepatic artery and the right portal vein) before parenchymal transection intraoperatively, it was evident that the blood supply to segment IV was arising from the right side. Sixty-one patients were excluded from liver donation on the basis of CT findings:

TABLE 1: Classification of Hepatic Arterial Supply Variant I

Description

Potential Contraindication for Liver Lobe Donation

PHA arises from CHA; RHA and LHA arise from PHA

Normal anatomy; no contraindication

II

Replaced LHA arises from LGA

No contraindication

III

Replaced RHA arises from SMA

No contraindication

IV

Variants II and III together

No contraindication

V

Accessory LHA arises from LGA

Potential issue for left lobe transplantation

VI

Accessory RHA arises from SMA

Potential issue for right lobe transplantation

VII

Variants V and VI together

Potential issue for left and right lobe transplantation, respectively

VIII

Replaced RHA and accessory LHA or replaced LHA and accessory RHA

Potential issue for left or right lobe transplantation, respectively

IX

Hepatic trunk arises from SMA

No contraindication

X

Hepatic trunk arises from LGA

No contraindication

XI

Any other variant

Variable

Note—Variants I–X are based on Michels [11]. PHA = proper hepatic artery, CHA = common hepatic artery, RHA = right hepatic artery, LHA = left hepatic artery, LGA = left gastric artery, SMA = superior mesenteric artery.

TABLE 2: 14 Patients With Anatomic Abnormalities Patient Intended Lobe No. for Donation

Hepatic Artery (Michels Classification)

Portal Vein

Hepatic Vein

Biliary Tree

1

Right

XI: segments VI and VII from LHA RPPV from MPV

Conventional

2

Right

VIII: segment VIII from accessory LHA

Trifurcation with accessory segment VIII from LPV

Accessory hepatic vein drains RPHD to LHD segment VI

Conventional

3

Right

XI: segment IV from RHA

LPV from RAPV

Accessory hepatic vein drains Segment IV to RAHD segment VI

4

Right

I

RPPV from MPV

Conventional

Accessory duct from segments V and VIII to LHD

5

Right

I

Conventional

Two accessory hepatic veins drain segment VI

Segment VI into CHD, segment VII into LHD

6

Right

XI: accessory segment IV from RHA

Segment II from MPV and then trifurcation

Conventional

Segments II and III drain into the CHD

7

Right

XI: 3 LHAs from PHA

Conventional

No RHV; all segments drain separately

RPHD to LHD; accessory duct from segments V and VI to CHD

8

Right

XI: segment VIII from LHA

Segments V and VIII from LPV

Separate segment V and VI into IVC

Conventional

9

Right

VIII: segment VIII from accessory LHA

Conventional

Conventional

Conventional

10

Left

I

Conventional

Conventional

RPHD to LHD

11

Left

I

Conventional

Accessory hepatic vein drains RPHD to LHD segment VI

12

Left

I

Conventional

Conventional

RPHD to LHD

13

Left

XI: segment IV from RHA

Conventional

Conventional

Conventional

14

Left

I

Conventional

Conventional

RPHD to LHD

Note—LHA = left hepatic artery, RPPV = right posterior portal vein, MPV = main portal vein, LPV = left portal vein, RPHD = right posterior hepatic duct, LHD = left hepatic duct, RHA = right hepatic artery, RAPV = right anterior portal vein, RAHD = right anterior hepatic duct, CHD = common hepatic duct, PHA = proper hepatic artery, RHV = right hepatic vein, IVC = inferior vena cava.

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Hahn et al.

A

B

Fig. 3—Volume-rendered obliquely oriented 3D image created from CT angiogram of 27-year-old woman (patient 1 in Table 2) being evaluated for right lobe liver donation. Image shows aberrant arterial anatomy in which arterial supply to segments VI and VII (curved arrow) is from left hepatic artery (dashed arrow). Also note common hepatic artery (short straight arrow), gastroduodenal artery (long straight arrow), and right hepatic artery (arrowhead).

Fig. 4—24-year-old male right lobe liver donor candidate (patient 8 in Table 2). A, Volume-rendered 3D image created from CT angiogram shows arterial supply to segment VIII (arrow) is from left hepatic artery. B, Coronal reformatted image obtained during portal phase shows portal venous blood supply to segment VIII (long arrow) is from left portal vein (short arrow). Other anomalies (not shown) in this patient included portal venous blood supply to segment V from left portal vein and separate hepatic venous drainage of segments V and VI into inferior vena cava.

40 (66%) had inadequate liver volumes, 14 (23%) had vascular or biliary anatomic abnormalities, five (8%) had steatosis, and two (3%) were found to have solid renal masses (pathologically proven renal cell carcinoma). Among the patients who were excluded on the basis of inadequate liver volumes, all were excluded for right lobe transplantation on the basis of insufficient remnant liver volume and all were excluded for left lobe transplantation on the basis of insufficient graft–body weight ratio. In most cases, the percentage of remnant liver volume was less than 35% and the graft–recipient weight ratio was less than 0.7% (Fig. 2).

Among the 14 patients with vascular or biliary anatomic abnormalities, eight had arterial variants (Figs. 3 and 4A). The most common arterial variant involved segment IV supply arising from the right hepatic artery (Table 2: patients 3, 6, 13). Segments of the right lobe of the liver were supplied by the left hepatic artery for four patients (Table 2: patients 1, 2, 8, and 9). Six patients had portal venous variants (Figs. 4B and 5), two of whom had trifurcation of the main portal vein into anterior and posterior right segmental veins and a left portal vein (Table 2: patients 2 and 6). These patients also had direct branches arising from

A

B

Fig. 5—18-year-old female right lobe liver donor candidate (patient 3 in Table 2). A, Axial contrast-enhanced CT image shows main portal vein (long arrow) and anterior right portal vein (short arrow). Note that left portal vein is not seen arising from main portal vein. B, Axial contrast-enhanced CT image shows intrahepatic portal venous connection (long arrow) between anterior right portal vein and left portal vein (short arrow), precluding right lobe donation.

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the left or main portal vein supplying different segments of the liver (Table 2: patients 2 and 6). Six patients had hepatic venous variants. Accessory inferior right hepatic veins were the most common hepatic vein variation, seen in four patients (Table 2: patients 2, 3, 5, and 11). Finally, 10 patients had biliary variants (Fig. 6). The most common biliary variant seen in our study was right posterior hepatic duct drainage into the left hepatic duct (Table 2: patients 2, 7, 10–12, 14). Of the patients who were excluded on the basis of anatomy, nine were excluded for right lobe donation; these patients all had sufficient

Fig. 6—35-year-old male liver donor candidate (patient 11 in Table 2). Volume-rendered 3D image created from CT cholangiogram shows right posterior hepatic duct (long arrow) draining into left hepatic duct (arrowhead), precluding left lobe donation. Note anterior right hepatic duct (short arrow). This patient was excluded from right hepatic lobe donation because of inadequate donor remnant liver volume.

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Radiographic Features of Potential Donor Livers right lobe volume but insufficient left lobe volume. The remaining five were excluded on the basis of inadequate volume for right lobe donation and anatomic variation precluding left lobe donation (Table 2). The left lobe volume for these potential donors would have been sufficient for transplantation. Discussion Preoperative imaging evaluation of potential liver donors is necessary to provide accurate volume measurements, depiction of vascular and biliary anatomy, and detection of diffuse or focal liver disease, which together guide the determination of donor suitability. In our donor series, the most frequent imaging feature that precluded donation was inadequate liver volume, which accounted for 66% of the donors who were excluded on the basis of anatomy. This finding is consistent with two studies [1, 10]; however, earlier studies tended to exclude few donors on the basis of liver volume [14–17], indicating that the centers have become more careful in protecting donors from postdonation morbidity and mortality. Adequate liver volume is essential for both donor and recipient liver function after transplantation. Although only 20–30% remnant liver volume is theoretically necessary for adequate hepatic function until the liver regenerates [3, 18], a minimum cutoff of 30–40% is typically used in the selection of donors. Larger remnant volumes are associated with lower donor complication rates [19]. The need to preserve donor remnant volume must be balanced by the need to provide adequate liver volume for the recipient, often defined by a graft–recipient weight ratio (graft size divided by recipient weight in kilograms) of more than 0.8% based on early studies. However, more recent evidence shows that a graft–recipient weight ratio of more than 0.6% is sufficient [20, 21]. Grafts that are too small for the recipient size are susceptible to hepatic dysfunction because of insufficient functional hepatic mass, and in addition, the hepatocytes may be injured by excessive portal perfusion. This phenomenon is called “small for size” syndrome [22]. Because data have become available showing that removal of the smaller part of the liver from a donor leads to fewer donor complications, centers including ours have started to perform more left lobe donation successfully via manipulation of the portal inflow in the recipient including splenic artery ligation, portacaval shunt, and pharmacologic manipulation of the portal

flow [20, 21]. Nevertheless, we believe that inadequate graft volume will continue to be the main anatomic reason for declining living donor candidates from donation. Vascular or biliary anatomic variants were present in 23% of excluded donors, with most of the variants involving the arterial and biliary systems. The reported frequencies with which anatomic variants excludes transplantation are extremely variable in the literature, with some institutions reporting almost no exclusion [1, 4, 14, 17] and others reporting anatomic variation as the primary reason for exclusion after imaging [9, 16]. The reason for this variability is unclear but may be related to the transplant surgeon’s experience and willingness to perform surgery on donors with more complex anatomy. Many of the arterial variants that we encountered included aberrant or accessory branches of right hepatic arteries that supplied the left lobe or vice versa, which can significantly complicate or preclude surgery [18]. The most common arterial variant involved segment IV supply arising from the right hepatic artery (Table 2: patients 3, 6, 13). Previously, this variant has been reported as a relative contraindication to right lobe donation [23, 24]. This anomaly alone does not preclude right lobe donation at our institution. Its presence is important to the transplant surgeon who would need to divide the right hepatic artery distal to the segment IV artery, which would ensure adequate blood supply to segment IV. However, this variant can preclude left lobe donation (Table 2: patient 13). Similarly, variants in which segments of the right lobe of the liver are supplied by the left hepatic artery (Table 2: patients 1, 2, 8, and 9) are a strong contraindication to right lobe donation [23]. For these cases, multiple arterial anastomoses would be necessary, and the decision to accept the donor candidate for donation is based on the size and length of the hepatic arteries because there is an increased risk for thrombosis after anastomosis [18, 25]. Portal venous anomalies occur in approximately 20% of patients. The reported most common variant is the absence of the right portal vein with trifurcation of the main portal vein into anterior and posterior right segmental veins and a left portal vein [26]. In our study, we encountered this variant in two patients (Table 2: patients 2 and 6) who also had direct branches arising from the left or main portal vein supplying different segments of the liver (Table 2: patients 2 and 6). A portal vein trifurcation is not considered a contraindica-

tion to liver donation in our center, and donation in this setting has had excellent outcomes. On the other hand, reports in the literature indicate that multiple anastomoses may need to be performed, which increases the risk of thrombosis [6, 26]. Portal vein variation is generally less common than variations in the hepatic arteries or hepatic veins [24], and modifications of the surgical technique can be made to the point that portal vein variation rarely precludes donation [5, 7]. In one case (Table 2: patient 3), the left portal vein came from the right anterior portal vein, which is an extremely rare variant that precluded donation [27]. The only other portal vein abnormality that precludes donation in our center is intrahepatic bifurcation of the portal vein. Accessory inferior right hepatic veins constituted the most common hepatic vein variation in our series and have been reported in 47–68% of patients in other series [16, 24]. Accessory veins that are larger than 5 mm require anastomosis to the inferior vena cava to prevent venous congestion of the corresponding liver, and a long distance of an accessory vein from the right hepatic vein can make implantation onto the recipient IVC challenging [16]; however, these modifications are carried out routinely at our institution. The most common biliary variant seen in our study was right posterior hepatic duct drainage into the left hepatic duct (Table 2: patients 2, 7, 10–12, 14), which has also previously been reported as the most common biliary variant in the literature [26]. This variant and others involving crossover of the right ductal system to the left or vice versa (Table 2: patients 3–7) necessitate multiple biliary anastomoses, resulting in a more complex operation in the case of right lobe donation; it is a contraindication to left lobe donation [6, 7, 10]. Preoperative evaluation of the biliary anatomy is critical because biliary complications, anastomotic leaks, and strictures are the most common causes of morbidity after living-donor liver transplantation [3]. Finally, a minority of patients were excluded on the basis of steatosis (8%) or other abnormalities incidentally found during CT evaluation (3%). In contrast, four of 15 (27%) patients excluded by Kamel et al. [16] were excluded because of steatosis, and 43% were excluded because of steatosis or focal lesions in a study by Salama et al. [9]. These different results may reflect the different populations from which donors were selected. The differences may also be related to an initial survey done for potential living donor candidates: It

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Hahn et al. is our center’s policy that candidates with a BMI of greater than or equal to 32 are excluded from evaluation automatically. We cannot directly compare our results with many reports in the literature because these studies generally do not address how many donors were excluded primarily on the basis of imaging findings: For instance, liver biopsy is not mandatory at all centers, and it is often unclear whether exclusion because of steatosis was based on imaging or biopsy findings. One limitation of this study is that the liver donor selection process differs according to the transplant center. Depending on the disposition and previous experience of transplant surgeons at different centers, some anatomic variations may preclude transplantation at one center and not at another; thus, studies from other institutions would be informative. In addition, there is no intraoperative correlation of the findings depicted at CT for the patients who did not go on to liver donation, so differences between the CT findings and the true anatomy may exist. In summary, anatomic variations of potential liver donors are common, and many of these variations result in exclusion of the potential donor from liver donation. We anticipate that this report and future reports of the reasons for donation preclusion will be informative for radiologists evaluating donor livers. Acknowledgment We thank the Yale Living Donor Liver Transplant coordinator, Katarzyna Cartiera, for her assistance in retrieving the chart information used in this study. References 1. Valentín-Gamazo C, Malagó M, Karliova M, et al. Experience after the evaluation of 700 potential donors for living donor liver transplantation in a single center. Liver Transpl 2004; 10:1087–1096 2. Alonso-Torres A, Fernández-Cuadrado J, Pinilla I, Parrón M, de Vicente E, López-Santamaría M. Multidetector CT in the evaluation of potential living donors for liver transplantation. RadioGraphics 2005; 25:1017–1030 3. Catalano OA, Singh AH, Uppot RN, Hahn PF,

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Ferrone CR, Sahani DV. Vascular and biliary variants in the liver: implications for liver surgery. RadioGraphics 2008; 28:359–378 4. Nakamura T, Tanaka K, Kiuchi T, et al. Anatomical variations and surgical strategies in right lobe living donor liver transplantation: lessons from 120 cases. Transplantation 2002; 73:1896–1903 5. Chen YS, Cheng YF, De Villa VH, et al. Evaluation of living liver donors. Transplantation 2003; 75(suppl):S16–S19 6. Low G, Wiebe E, Walji AH, Bigam DL. Imaging evaluation of potential donors in living-donor liver transplantation. Clin Radiol 2008; 63:136–145 7. Limanond P, Raman SS, Ghobrial RM, Busuttil RW, Saab S, Lu DS. Preoperative imaging in adult-to-adult living related liver transplant donors: what surgeons want to know. J Comput Assist Tomogr 2004; 28:149–157 8. Uchida K, Taniguchi M, Shimamura T, et al. Three-dimensional computed tomography scan analysis of hepatic vasculatures in the donor liver for living donor liver transplantation. Liver Transpl 2010; 16:1062–1068 9. Salama IA, Dessouky BA, Korayem EM, Aal SA. Impact of multislice spiral computed tomography on donor selection and surgical planning in livingrelated liver transplant. Exp Clin Transplant 2010; 8:111–124 10. Tsang LL, Chen CL, Huang TL, et al. Preoperative imaging evaluation of potential living liver donors: reasons for exclusion from donation in adult living donor liver transplantation. Transplant Proc 2008; 40:2460–2462 11. Michels NA. Blood supply and anatomy of the upper abdominal organs, with a descriptive atlas. Philadelphia, PA: Lippincott, 1955 12. Yajima Y, Narui T, Ishii M, et al. Computed tomography in the diagnosis of fatty liver: total lipid content and computed tomography number. Tohoku J Exp Med 1982; 136:337–342 13. Park YS, Park SH, Lee SS, et al. Biopsy-proven nonsteatotic liver in adults: estimation of reference range for difference in attenuation between the liver and the spleen at nonenhanced CT. Radiology 2011; 258:760–766 14. Pascher A, Sauer IM, Walter M, et al. Donor evaluation, donor risks, donor outcome, and donor quality of life in adult-to-adult living donor liver transplantation. Liver Transpl 2002; 8:829–837

15. Pomfret EA, Pomposelli JJ, Lewis WD, et al. Live donor adult liver transplantation using right lobe grafts: donor evaluation and surgical outcome. Arch Surg 2001; 136:425–433 16. Kamel IR, Kruskal JB, Pomfret EA, Keogan MT, Warmbrand G, Raptopoulos V. Impact of multidetector CT on donor selection and surgical planning before living adult right lobe liver transplantation. AJR 2001; 176:193–200 17. Marcos A, Fisher RA, Ham JM, et al. Selection and outcome of living donors for adult to adult right lobe transplantation. Transplantation 2000; 69:2410–2415 18. Brandhagen D, Fidler J, Rosen C. Evaluation of the donor liver for living donor liver transplantation. Liver Transpl 2003; 9(suppl 2):S16–S28 19. Reichman TW, Sandroussi C, Azouz SM, et al. Living donor hepatectomy: the importance of the residual liver volume. Liver Transpl 2011; 17:1404–1411 20. Selzner M, Kashfi A, Cattral MS, et al. A graft to body weight ratio less than 0.8 does not exclude adult-to-adult right-lobe living donor liver transplantation. Liver Transpl 2009; 15:1776–1782 21. Ikegami T, Masuda Y, Ohno Y, et al. Prognosis of adult patients transplanted with liver grafts < 35% of their standard liver volume. Liver Transpl 2009; 15:1622–1630 22. Emond JC, Renz JF, Ferrell LD, et al. Functional analysis of grafts from living donors: implications for the treatment of older recipients. Ann Surg 1996; 224:544–552; discussion, 552–554 23. Kostelic JK, Piper JB, Leef JA, et al. Angiographic selection criteria for living related liver transplant donors. AJR 1996; 166:1103–1108 24. Erbay N, Raptopoulos V, Pomfret EA, Kamel IR, Kruskal JB. Living donor liver transplantation in adults: vascular variants important in surgical planning for donors and recipients. AJR 2003; 181:109–114 25. López-Andújar R, Moya A, Montalvá E, et al. Lessons learned from anatomic variants of the hepatic artery in 1,081 transplanted livers. Liver Transpl 2007; 13:1401–1404 26. Mortelé KJ, Cantisani V, Troisi R, de Hemptinne B, Silverman SG. Preoperative liver donor evaluation: imaging and pitfalls. Liver Transpl 2003; 9:S6–S14 27. Atri M, Bret PM, Fraser-Hill MA. Intrahepatic portal venous variations: prevalence with US. Radiology 1992; 184:157–158

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