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ORIGINAL ARTICLE
Year : 2014  |  Volume : 27  |  Issue : 1  |  Page : 157-163

Role of three-dimensional multidetector computed tomography angiography of hepatic vessels in the evaluation of living donors


Radiology Department, Faculty of Medicine, Menoufia University, Menoufia, Egypt

Date of Submission18-Mar-2013
Date of Acceptance12-Aug-2013
Date of Web Publication20-May-2014

Correspondence Address:
Hazem M. Elshazly
MBBCh, Elgalaa St. Elsanta, 31111 Gharbeya Governorate
Egypt
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Source of Support: None, Conflict of Interest: None


Read associated Erratum: Erratum with this article

DOI: 10.4103/1110-2098.132791

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  Abstract 

Objectives
To assess the role of multidetector computed tomography (MDCT) angiography in the preoperative mapping of hepatic vascular anatomy in potential living liver donors, identification of anatomical variants that influence the donor selection and surgical planning.
Background
Liver transplantation became the ultimate solution for decompensating liver diseases. Donor's safety and selection protocols are primary concerns. Thus, preoperative evaluation of the hepatic vascular anatomy is crucial to minimize mortality, morbidity, and post-transplant complications.
Patients and methods
Evaluation of 20 potential living donors was performed using 64-row MDCT scanners, obtaining hepatic arterial and portovenous phases. The arterial anatomy was classified according to the Michels classification. The portal venous anatomy was assessed and classified according to the Cheng classification. The hepatic venous anatomy was evaluated with special attention paid to the middle hepatic vein anatomy.
Results
In our study, out of 20 liver transplantation potential donors, 11 (55%) showed a classic arterial anatomy, whereas nine (45%) showed some type of anatomical variant. Replaced right hepatic artery from the superior mesenteric artery was the most common (three donors, 15%). The classic portal venous anatomy was found in 16 candidates (80%), whereas its variants were detected in four cases (20%). The standard hepatic venous anatomy was found in 14 candidates (70%). Six individuals (20%) had significant accessory hepatic veins. Middle hepatic vein confluence was late in four candidates (20%). An accessory inferior right hepatic vein was the most common accessory hepatic vein that was detected in five cases (25%).
Conclusion
64-row MDCT is essential in the preoperative evaluation of potential liver donors. It is a noninvasive comprehensive evaluation tool that can show the hepatic vascular anatomic details with precise relationship to the liver parenchyma.

Keywords: Hepatic artery, hepatic vein, liver transplantation, multidetector computed tomography angiography, portal vein


How to cite this article:
Elkholy MR, Elshazly HM. Role of three-dimensional multidetector computed tomography angiography of hepatic vessels in the evaluation of living donors. Menoufia Med J 2014;27:157-63

How to cite this URL:
Elkholy MR, Elshazly HM. Role of three-dimensional multidetector computed tomography angiography of hepatic vessels in the evaluation of living donors. Menoufia Med J [serial online] 2014 [cited 2018 Jun 18];27:157-63. Available from: http://www.mmj.eg.net/text.asp?2014/27/1/157/132791


  Introduction Top


Liver transplantation, recently, has become the ultimate solution for decompensating liver diseases such as chronic liver failure, acute liver failure, primary hepatic malignancy, and inborn errors of metabolism [1].

The satisfactory outcome of liver transplantation has led to an insufficient supply of deceased donor organs; hence, surgeons are concentrating on developing and performing living donor liver transplantations (LDLTs), particularly for young pediatric patients and adults who are disadvantaged by the current deceased donor allocation system [2].

Because LDLT may cause morbidity in an otherwise healthy donor, donor's safety is a primary concern, and selection protocols are of crucial importance to exclude unsuitable candidates for either medical or anatomical reasons [3].

Ideally, there would be no need to subject perfectly healthy people in the prime of their lives to a potentially life-threatening operation to procure these transplantable organs. Donor selection and evaluation have become highly specialized, because donor safety is imperative and cannot be compromised regardless of the consequences for the intended recipient, even death; there can be no exception to that rule [4].

Thus, preoperative imaging evaluation of the hepatic vascular anatomy is crucial for surgical planning and has been shown to minimize mortality and morbidity for both donor and recipient, and to minimize post-transplant complications [3].

The multidetector computed tomography (MDCT) protocol permits the assessment of the hepatic parenchymal morphology and volume, in conjunction with detailed and accurate analysis of the biliary and vascular anatomy, thereby obviating arterial digital subtraction angiography (DSA) or endoscopic retrograde cholangiopancreatography (ERCP) as part of the preharvest protocol [5].


  Aim of the work Top


This study is designed to assess the role of MDCT angiography in the preoperative evaluation of living liver donors.


  Patients and methods Top


Our study included 20 potential adult-to-adult living liver donors. They were 12 men and eight women, with a mean age of 35.4 years (age range, 20-55 years). All donors were of average weight and physically fit for operation, with no history of any medical diseases. The study was carried out from December 2009 to August 2011. All donors underwent precontrast and triphasic study using 64-row MDCT scanner.

Precontrast and postcontrast were obtained through the entire liver.

Image processing and interpretation

Anterior three dimensional volume rendered computed tomography inage of the liver [Figure 1], obtained at the level of hte portal vein, shows the anticipated hepatectomy plane extending inferiorly immediately to the right of the middle hepatic vein (MHV). The left lobe, which will remain in the donor, also has a surface-shaded rendering of the hepatic veins superimposed. Note the veins drainign into the MHV (arrows), which traverse the hepatectomy plane.

Evaluation of the hepatic parenchyma: The hepatic parenchyma was evaluated by the exclusion of diffuse liver disease and exclusion of focal lesions.

Reconstruction of the hepatic vasculature: The technique was considered technically adequate if arterial images allowed complete opacification of tertiary-order branches and portal venous-phase images allowed complete opacification of the small vessels (<3 mm).
Figure 1:

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The hepatic arterial anatomy was categorized according to the Michels classification for the origins of the right hepatic artery (RHA) and the left hepatic artery (LHA) and the presence of any accessory hepatic arteries [Figure 2]. The classic arterial anatomy (type I) is shown as a divided common hepatic artery, a branch of the celiac trunk, into approximately equal-sized right and left hepatic arteries before entering the liver at the porta hepatis [Figure 9].

If the segment IV artery originates from the RHA, the RHA should be clamped after it gives off the segment IV artery; hence, the distance between its origin and the origin of the RHA is important because it provides a reference for the surgeon during graft harvesting [Figure 3]; the distance has to be in a range of 9-22 m to allow sparing of segment IV during surgery; otherwise, the left lobe medial segment that remains in the donor will develop ischemia and the metabolic needs of the donor may not be met during the regeneration process.
Figure 2:

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Figure 3:

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The variations of the portal vein were analyzed by the Cheng classification. In the classic portal venous anatomy, we measured the length of the right and the left portal veins as well as the distance between the bifurcation of the main portal vein and that of the right portal vein [Figure 4]. Detection of portal vein trifurcation was made in some cases [Figure 5]; another important variation is the low-inserting right posterior portal vein (RPPV) [Figure 6]. Special attention was paid to the detection of undivided main portal veins, which is an absolute contraindication to liver donation.
Figure 4:

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Figure 5:

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Figure 6:

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In cases of main portal vein trifurcation, there is no segment of the portal vein onto which a clamp can be placed, and so anastomosis of the two portal veins is required during the right lobe transplantation. This increases the risk of postoperative portal vein thrombosis. In cases of low-inserting RPPV, anastomosis of the two portal veins is required during right lobe transplantation.

A triplet of hepatic veins draining separately into the inferior vena cava (IVC) was considered as the classic anatomy [Figure 7]. The middle hepatic vein (MHV) was of special interest, especially its confluence with the IVC; it was considered as an early confluence when found away from IVC, resulting in a small graft size, which may not be sufficient to maintain the recipient's metabolic function. However, MHV confluence was considered to be late if it was very close to the IVC. MHV dominance over the right hepatic vein (RHV) must also be detected (i.e. MHV provides drainage for a large portion of the right lobe).

We also focused on the evaluation of significant accessory hepatic vein that crosses the dissection line or that may require additional anastomosis, and when found, its size and distance from the RHV were identified in the coronal images [Figure 8]; when the distance between the RHV and the accessory inferior RHV is more than 4 cm, it was difficult to surgically implant both veins with a single partially occluding clamp on the recipient's IVC, which cause the surgical procedure to be more difficult and more time consuming.
Figure 7:

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Figure 8:

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The size of the accessory inferior RHV is also very important in the preoperative planning. If the cross-sectional diameter is greater than 5 mm, the vessel has to be preserved and reanastomosed in the recipient's IVC; otherwise, it can result in a congested graft and lead to organ rejection.


  Results Top


64-row MDCT was carried out for 20 potential living donors, 12 men and eight women with a mean age of 35.4 years [Table 1]. Optimum arterial and venous opacification was achieved fairly in all donors.
Table 1: The study population is summarized as follows

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Hepatic arterial anatomy

Identification of the hepatic arteries and their main branches was possible in all patients. Considering the Michels classification, standard arterial anatomy (type I) was determined in 11 cases (55%) [Figure 9], whereas two cases (10%) showed a replaced LHA arising from the left gastric artery (type II) and three cases (15%) had a replaced RHA arising from the superior mesenteric artery (SMA) (type III) [Figure 10]. One case (5%) had an association of the replaced LHA with the replaced RHA (type IV), one case (5%) with the accessory LHA (type V) and two cases (10%) with the accessory RHA (type VI) [Figure 11].

The dominant arterial branch to segment IV was a branch from the LHA in 15 cases (75%), whereas it branched from the RHA in five cases (25%); its diameter and distance from the RHA origin were measured [Figure 3] and [Table 2].
Figure 9:

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Figure 10:

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Figure 11:

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Table 2: Hepatic arterial anatomical variants

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Portal venous anatomy

Classic portal venous anatomy in which the main portal vein bifurcates into left and right portal veins was found in 16 candidates (80%) [Figure 4]; meanwhile, three candidates (15%) presented with trifurcation [Figure 5], whereas low insertion of the RPPV originating from the main portal vein was detected in one case (5%) [Figure 6] and [Table 3].
Table 3: Portal venous anatomy variants

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Hepatic venous anatomy

Standard hepatic venous anatomy (a triplet of hepatic veins draining separately into the IVC) was found in 14 candidates (70%) [Figure 7]. Six candidates (30%) presented hepatic venous drainage variants. The level of MHV confluence was late, which may alter the plane for right hepatectomy in four candidates (20%), whereas in the other 16 cases (80%), confluence was early.

Significant accessory hepatic veins were detected, of which four cases (20%) had a single significant accessory hepatic vein [Figure 8], whereas two cases (10%) had two or more significant accessory hepatic veins; the most common type was the accessory inferior RHV as detected in five cases (25%) [Table 4].
Table 4: Hepatic venous anatomy

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  Discussion Top


MDCT is now the most important tool that can provide valuable information in the assessment of potential liver donors [7]. It is essential to define the anatomical variants of hepatic vessels, especially those considered relative or absolute contraindications for donation, those requiring multiple anastomoses and those altering the surgical approach [8].

In our study, the classic hepatic arterial anatomy was found in 11 cases (55%), whereas in a total of nine (45%) cases variants were detected. The frequency of the type III variant (replaced RHA arising from the SMA) was the highest, detected in 15% of the cases (n = 3), whereas the second most common variant was type VI (accessory RHA) (n = 2, 10%). Type II was detected in 10% (n = 2), whereas types IV and V were shown in one case (5%) each.

Our results coincide with the study by Michels [9], who established a classification system for hepatic arterial anatomy and its variants. These hepatic arterial variants were reported to be present in ∼41-46% of cases [10]. Several reports showed that the most common variants are replaced or accessory RHA arising from the SMA and a replaced or accessory LHA arising from the left gastric artery [11].

This is supported by the study carried out by Artioli et al. [12], in which the most common variant was a replaced RHA arising from the SMA (type III). The type III variant was also the dominant variant reported by Ozsoy et al. [13]. In contrast, equal dominance of type III and type V variants was reported by Lee et al. [14] and by Kamel et al. [15].

A replaced RHA or LHA has the advantage of safer anastomosis because these arteries are usually longer [16]. In contrast, the presence of an accessory RHA or LHA may indicate the creation of a dual anastomosis because hepatic arteries are considered end arteries [17].

The arterial supply of segment IV arises from the RHA in 25-30% of the cases [10]; therefore, its precise identification as well as the determination of its distance from the proper hepatic artery bifurcation is necessary [11].

In our study, MDCT was able to identify the dominant artery to segment IV in all cases. It was a branch from LHA in the majority of the cases (n = 15, 75%), whereas it was a branch from RHA in 25% of the cases (n = 5). This is in agreement with the results of Kamel et al. [15].

The sensitivity, specificity and accuracy of MDCT in the identification of hepatic artery anatomy were all 100%; these results support the results of earlier studies carried out by Artioli et al. [12]. In addition, this matches with the results of Schroeder et al. [5], who reported a similar accuracy of MDCT.

The most common variant in portal venous anatomy is trifurcation into the right anterior, the right posterior, and the left portal venous branches, which represents about 7-16% of the patients [11]. It is important to be identified preoperatively as it needs surgical reconstruction in cases of right lobe donation. In contrast, an undivided main portal vein is considered as an absolute contraindication for right lobe donation [7].

In our study, a conventional anatomy of the portal vein was identified in 16 cases (80%), whereas the main portal vein trifurcation constituted the most common variant (n = 3, 15%); we encountered one case (5%) with RPPV originating from the main portal vein. Our results were close to earlier reports, where several series reported anatomical variants of the portal system to be ∼20-26% of the donor population [10].

In the series of Ozsoy et al. [13] on 496 Turkish liver donors, conventional anatomy was the most common (n = 390, 78.6%), whereas trifurcation was observed in 12.7% (63 donors). In a large cohort study carried out by Koc et al. [18], they reported classic (normal) branching of the portal vein in 1087 of a total of 1396 patients included in their study (78.5%), whereas trifurcation of portal vein was the second common type found in 154 (11.1%) patients. The next most common variation was a right posterior portal vein branch that was the first branch of the main portal vein (n = 134, 9.7%).

The hepatic venous anatomy identification is also important for liver transplantation; multiple hepatic venous variants exist, but their importance varies; in our series, we paid special attention to the significant accessory hepatic vein (>5 mm) that crosses the dissection line or that may require additional anastomosis. MHV anatomy is actually the key to right lobe donation because the hepatectomy plane runs 1 cm to the right of the MHV, with the subsequent necessity of transaction of one or more of its branches. This situation is more common with late confluence of branches forming the MHV or dominance of the MHV over the RHV (MHV drains a large portion of the right lobe) [10]. In our study, we identified 14 cases (70%) with classic hepatic vein anatomy, with a triplet of hepatic veins draining separately into the IVC, whereas six (30%) cases had one or more anatomical variants.

MDCT was able to evaluate the MHV confluence, and we encountered four cases (20%) with late confluence of MHV. A single significant accessory hepatic vein was also identified in four cases (20%), whereas two or more significant hepatic veins were found in two cases (10%). The right inferior hepatic vein was the most common and was detected in five cases (25%). Our results are closer to the results of Goyen et al. [19], who reported hepatic venous system variations in 45/150 cases (30%). In contrast, Artioli et al. [12] reported standard hepatic venous anatomy in only 8/32 (25%) of their candidates, whereas 24/32 candidates (75%) presented with variants of the hepatic venous drainage.

Artioli et al. [12] series of 32 potential liver donors reported that 17 of their cases had accessory right lobe veins draining in the IVC and 15 cases had accessory branches draining in the MHV crossing the dissection line. Other studies reported two or more accessory hepatic veins in 12-15% of the cases, whereas the most common hepatic venous variant was an accessory inferior RHV [20].

MDCT was able to identify important vascular variants that influence patient selection and surgical planning, such as trifurcation of portal vein, whereas none of the vascular variants in this study was considered as an absolute contraindication to liver transplantation. 64-row MDCT examination of the liver provided satisfactory and comprehensive vascular mapping for potential donors before liver transplantation. The data provided had paramount importance in candidate selection to ensure donor safety and in surgical planning. Our data support previous results [21] that concluded that MDCT scans can depict the vascular anatomy accurately in a way that is helpful to the surgeon.


  Conclusion Top


LDLT is increasingly being used to help compensate for the increasing shortage of cadaveric liver grafts. However, the extreme variability of hepatic vascular systems can impede this surgical procedure. Detailed knowledge of the hepatic angioarchitecture is essential to ensure safe and successful liver surgery.

Evaluation of potential living donors was conducted using a 64-row MDCT scanner to obtain arterial-phase and portal dominant-phase images after intravenous injection of the contrast material, after which three-dimensional maximum intensity projection (MIP) and volume rendering (VR) images were created; the vascular anatomy was evaluated, with special attention given to the presence of variants, especially those considered relative or absolute contraindications for donation, those requiring reconstruction or those potentially altering the surgical approach.

In conclusion, 64-row MDCT angiography is an essential part of preoperative evaluation of potential donors. It is a noninvasive comprehensive evaluation tool that can show the hepatic vascular anatomic details with precise demonstration of its relationship to liver parenchyma.


  Acknowledgements Top


Conflicts of interest

There are no conflicts of interest.

 
  References Top

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