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Liver Transplantation: Preoperative CT Evaluation¹

¹ From the Russell H. Morgan Department of Radiology and Radiological Science (H.K.P., E.K.F.) and Department of Surgery (W.R.M.), Johns Hopkins Hospital, 600 N Wolfe St, Baltimore, MD 21287. Recipient of a Certificate of Merit award for an education exhibit at the 2000 RSNA scientific assembly. Received January 19, 2001; revision requested March 2 and received April 16; accepted April 25. Address correspondence to H.K.P. (e-mail: hpannu@jhmi.edu).

	Abstract

Top Abstract Introduction Surgical Technique: An Overview CT Protocol Evaluation in Recipients Evaluation in Living Donors Summary References

 
Liver transplantation is a successful therapeutic option for patients with chronic liver disease and liver failure in that 1-year survival is greater than 80%. Orthotopic transplantation is usually performed from a cadaveric or living adult donor. The necessary evaluation of recipients and donors prior to transplantation can be successfully performed with computed tomography (CT). CT is useful in determining clinically relevant information for recipients such as size of the caudate lobe, exclusion of advanced hepatocellular carcinoma and other malignancy, patency of the venous system, presence of perihepatic varices, patency of the celiac artery, exclusion of splenic artery aneurysm, and position of iatrogenic venous shunts. CT in living donors may help to determine clinically relevant information about variant hepatic arterial anatomy, source of the artery to segment IV, intraparenchymal anatomy of the hepatic veins and accessory hepatic veins, trifurcation of the portal vein or hepatic duct, liver volume, and fatty change of the parenchyma. Surgical approaches and the imaging findings that influence management are reviewed.

Index Terms: Hepatic arteries, CT, 952.12914 • Hepatic veins, CT, 957.12914 • Liver, CT, 761.12114 • Liver, transplantation, 761.459

	Introduction

Top Abstract Introduction Surgical Technique: An Overview CT Protocol Evaluation in Recipients Evaluation in Living Donors Summary References

 
Orthotopic liver transplantation is the mainstay of therapy for multiple irreversible acute and chronic liver diseases. Survival after transplantation has been improved owing to advances in immunosuppressive therapy and surgical techniques that allow patients to live many years after transplantation. The 5-year survival is 65%–78% (1). Approximately 4,000 liver transplantations are performed each year, with the majority of livers coming from cadaveric donors (2). Since the number of transplantation candidates is greater than the availability of cadaveric livers, techniques such as split-liver donation and living donor transplantation have been developed. Split-liver donation involves dividing a cadaveric liver so that the lateral segment of the left lobe may be transplanted into a pediatric patient and the remainder of the liver may be transplanted into an adult. In living donor transplantation, the donor undergoes partial hepatectomy for donation to a recipient. If the recipient is a child, the left lateral segment is used for donation. If the recipient is an adult, the right lobe of the liver is usually donated, although occasionally the left lobe is sufficient.

Successful transplantation requires thorough evaluation of the condition of the transplantation candidate and that of the potential living donor. Noninvasive imaging with computed tomography (CT) has a role in the evaluation of both. In this article, we discuss the utility of CT in preoperative assessment of liver transplantation and donation. Specific questions that can be answered with CT and the influence of the imaging findings on the management of cases are reviewed. Since surgical technique varies slightly between cadaveric and living donation, the surgical method for each is first briefly reviewed. CT protocols for single-detector and multidetector scanners are also presented.

	Surgical Technique: An Overview

Top Abstract Introduction Surgical Technique: An Overview CT Protocol Evaluation in Recipients Evaluation in Living Donors Summary References

 
Hepatectomy
The recipient undergoes total hepatectomy. The hepatic artery, portal vein, and common hepatic duct are ligated close to the liver. The intrahepatic inferior vena cava is typically resected for cadaveric transplantation but may be left intact in cases in which an end-to-side anastomosis is performed between the native and cadaveric inferior venae cavae. The recipient inferior vena cava is preserved for living donor transplantation. The diseased liver is removed. A partial hepatectomy is performed in living donors. The hepatic artery, portal and hepatic veins, and bile duct of the graft lobe are isolated. The hepatic parenchyma is then dissected to isolate the graft lobe, and it is removed.

Implantation of the Graft in the Recipient
The donor and recipient inferior venae cavae and portal veins are anastomosed for cadaveric transplantations. The donor hepatic vein is anastomosed to the recipient inferior vena cava for living donor transplantation. The donor hepatic artery is anastomosed to the recipient hepatic artery. A duct-to-duct anastomosis is performed, or a hepaticojejunostomy is constructed.

	CT Protocol

Top Abstract Introduction Surgical Technique: An Overview CT Protocol Evaluation in Recipients Evaluation in Living Donors Summary References

 
Single-Detector Spiral CT
Helical scanning is performed through the liver after the ingestion of 750 mL of water as a negative oral contrast agent and intravenous injection of 150 mL of nonionic contrast material. Rates of contrast material injection of 4–5 mL/sec are reported in the literature. We use a delay of 25 seconds for scanning during the arterial phase and a delay of 55 seconds for the venous phase. Scanning collimation is 3 mm, table speed is 6 mm/sec, pitch is 2, and reconstruction interval is 1–2 mm for the arterial and the venous phase.

Multidetector Spiral CT
The injection parameters and scan delay are the same as those used with a single-detector scanner except for a decrease in contrast material volume to 120 mL. The section collimation is 1.0 mm, and reconstructed section width is 1.25 mm for the arterial and venous phases, with the scan reconstructed every 1 mm.

Techniques to display the acquired data in three dimensions include volume rendering and maximum intensity projection. We typically use volume rendering, as the entire data set is displayed, unlike maximum intensity projection, in which only a fraction of the data is available. With volume rendering, a wide range of opacity settings can be manipulated to show vessels of various sizes and to separate overlapping structures.

	Evaluation in Recipients

Top Abstract Introduction Surgical Technique: An Overview CT Protocol Evaluation in Recipients Evaluation in Living Donors Summary References

 
CT assessment in recipients includes evaluation of the liver parenchyma and vasculature. Exclusion of intrahepatic and extrahepatic malignancy, venous thrombosis, extensive perihepatic varices, celiac stenosis, splenic artery aneurysm, and incorrect location of a transjugular portosystemic shunt is clinically helpful (1). The gallbladder is removed in all cases; therefore, identification of abnormalities in it usually does not alter the surgical plan.

Evaluation of Liver Parenchyma
The liver can appear normal in 25% of patients with cirrhosis (3). However, the contour of the cirrhotic liver is usually nodular, and there are atrophy of the right lobe and hypertrophy of the lateral segment and caudate lobe (Fig 1). The caudate lobe can become enlarged and surround the inferior vena cava. Exposure of the inferior vena cava and removal of the liver from the retrohepatic portion of the inferior vena cava is difficult in such cases (Fig 2). This situation becomes relevant in cases of living donor transplantation in which the cava is preserved.

View larger version (162K): [in this window] [in a new window] [Download PPT slide]   Figure 1.   Nodular liver and enlargement of the left lobe in a 49-year-old female liver transplantation candidate with cryptogenic cirrhosis. CT scan of the abdomen obtained with intravenous administration of contrast material shows that the left lobe of the liver (solid arrow) is enlarged and the right lobe (open arrow) is atrophied. The contour of both lobes is nodular. The spleen is also enlarged.

View larger version (164K): [in this window] [in a new window] [Download PPT slide]   Figure 2.   Enlarged caudate lobe in a 54-year-old female liver transplantation candidate with cirrhosis secondary to alcohol use. CT scan of the abdomen obtained with intravenous contrast material shows that the caudate lobe (*) is hypertrophied and wrapped around the inferior vena cava (arrow). There is also relative atrophy of the right lobe, and the liver contour is nodular.

Eighty percent of hepatocellular carcinomas larger than 2 cm in diameter are detected at multiphase CT (6). The presence of fibrosis, fatty infiltration, necrosis, or regenerative nodules can make the detection of tumors in cirrhotic livers difficult (7). The attenuation of tumors is variable on enhanced and nonenhanced scans (8). On images obtained without the administration of contrast material, the tumors are usually hypoattenuating (9). Isoattenuating tumors may have a low-attenuation tumor capsule (9). Hepatocellular carcinomas are hyperattenuating or of mixed attenuation on the arterial-phase images obtained in the majority of patients (10). Small tumors tend to be homogeneously hyperattenuating (8). More than 90% of tumors detected at CT are seen on arterial-phase images, and 10% are seen only during this phase (9,10). Hepatocellular carcinomas are hypo- or isoattenuating compared with the appearance of liver parenchyma on portal-venous-phase images (Fig 3) (9). This pattern is due to supply of the tumor by the hepatic artery. Other findings are nodules of mixed attenuation and delayed capsular enhancement (9). On unenhanced scans, hypo- and hyperattenuating areas in the tumor are due to fat and blood, respectively. Other causes of variable attenuation of the tumors are necrosis due to tumor degeneration and deposition of iron. Calcification occurs in 5%–10% of cases. Poorly differentiated tumors tend to be infiltrating.

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 3a.   Hepatocellular carcinoma confined to the liver—not a contraindication to transplantation—in a 47-year-old female transplantation candidate with cirrhosis secondary to hepatitis C. CT of the abdomen was performed with the use of intravenous contrast material. (a) Arterial-phase CT scan shows a hypervascular mass (black arrow) in the right lobe of the liver that is compatible with hepatocellular carcinoma. Soft-tissue-attenuation structures (white arrows) are present in the retroperitoneum. (b) CT scan obtained during the portal venous phase shows these structures to be periportal nodes (open arrow) and varices (solid arrow). (c) CT scan obtained superior to b shows a second hypervascular lesion (arrow) that was discovered to be a moderately well differentiated hepatocellular carcinoma at biopsy. Since the diameters of both lesions are less than 3 cm, transplantation may be performed. Because of the presence of cancer, attempts were made to expedite surgery in this patient.

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 3b.   Hepatocellular carcinoma confined to the liver—not a contraindication to transplantation—in a 47-year-old female transplantation candidate with cirrhosis secondary to hepatitis C. CT of the abdomen was performed with the use of intravenous contrast material. (a) Arterial-phase CT scan shows a hypervascular mass (black arrow) in the right lobe of the liver that is compatible with hepatocellular carcinoma. Soft-tissue-attenuation structures (white arrows) are present in the retroperitoneum. (b) CT scan obtained during the portal venous phase shows these structures to be periportal nodes (open arrow) and varices (solid arrow). (c) CT scan obtained superior to b shows a second hypervascular lesion (arrow) that was discovered to be a moderately well differentiated hepatocellular carcinoma at biopsy. Since the diameters of both lesions are less than 3 cm, transplantation may be performed. Because of the presence of cancer, attempts were made to expedite surgery in this patient.

View larger version (163K): [in this window] [in a new window] [Download PPT slide]   Figure 3c.   Hepatocellular carcinoma confined to the liver—not a contraindication to transplantation—in a 47-year-old female transplantation candidate with cirrhosis secondary to hepatitis C. CT of the abdomen was performed with the use of intravenous contrast material. (a) Arterial-phase CT scan shows a hypervascular mass (black arrow) in the right lobe of the liver that is compatible with hepatocellular carcinoma. Soft-tissue-attenuation structures (white arrows) are present in the retroperitoneum. (b) CT scan obtained during the portal venous phase shows these structures to be periportal nodes (open arrow) and varices (solid arrow). (c) CT scan obtained superior to b shows a second hypervascular lesion (arrow) that was discovered to be a moderately well differentiated hepatocellular carcinoma at biopsy. Since the diameters of both lesions are less than 3 cm, transplantation may be performed. Because of the presence of cancer, attempts were made to expedite surgery in this patient.

Presence of Cholangiocarcinoma and Other Malignancies
Known cholangiocarcinoma, especially a hilar tumor, is an absolute contraindication to liver transplantation due to a high recurrence rate of 44% (1,11). Tumors tend to recur early, and the 5-year survival ranges from 7% to 17% (11). Although a strong association does not exist between cirrhosis and cholangiocarcinoma, patients with conditions such as primary sclerosing cholangitis are at increased risk for the development of this malignancy (9). Detection of a primary tumor outside the liver, with or without hepatic metastases, is also an absolute contraindication to transplantation. Hepatic metastases have a recurrence rate of almost 60% after transplantation (11).

Intrahepatic cholangiocarcinoma represents 10% of primary cholangiocarcinomas (12). With the injection of contrast material, there is usually early peripheral enhancement with progressive filling of the lesion (Fig 4) (12). Delayed enhancement of the center is due to diffusion of contrast material into the extravascular space of fibrous tissue in the tumor (12–14). A peripheral low-attenuation halo can produce a bull’s-eye appearance. Hilar tumors are infiltrating or exophytic (15). Hilar tumors of the infiltrating stenotic variety can be hyperattenuating on arterial-phase images (15). Intraductal tumors appear as hypoattenuating masses in dilated ducts on enhanced scans (13). Masses greater than 1 cm in diameter can be seen, and the ductal dilatation is segmental or lobar (13). In some cases, the dilated ducts can appear hyperattenuating due to tumor casts (13).

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 4.   Intrahepatic cholangiocarcinoma—a contraindication to transplantation—in a 46-year-old female liver transplantation candidate with sclerosing cholangitis and end-stage liver disease. CT scan of the abdomen obtained with intravenous and oral contrast material shows a hypoattenuating mass in the left lobe of the liver (arrow) that is compatible with tumor. Cholangiocarcinoma was diagnosed by means of percutaneous biopsy. Although the patient was previously considered for transplantation, she was no longer a candidate after imaging. Metastatic disease in the pelvis was also detected (not shown).

Patency of the Portal Vein and Superior Mesenteric Vein
Portal venous thrombosis is seen in 15% of patients with chronic liver disease (16). Thrombosis is due to increased resistance in the liver and resultant slow venous flow (17). Although thrombosis of the portal vein was initially considered an absolute contraindication to liver transplantation, a variety of surgical techniques are now used in cases of portal venous abnormalities (1,16). If acute portal thrombus is present, manual thrombectomy is performed at surgery (16). If chronic portal venous thrombosis is present or the portal vein diameter is less than 4 mm, the donor portal vein is anastomosed to the splenomesenteric confluence, the superior mesenteric vein, or a splenic varix (16,18,19). If the graft portal vein is not long enough to reach the confluence, an iliac vein graft is obtained from the donor (18). Higher recipient morbidity due to uncontrolled bleeding has been seen in patients with phlebitis that is present with thrombosis (16). Diffuse thrombosis of the portal and superior mesenteric veins remains a contraindication to liver transplantation.

On unenhanced CT images, the attenuation of acute thrombus is approximately 60–70 HU (20). At CT performed with intravenous contrast material, the acute thrombus is a hypoattenuating filling defect in the portal vein with partial or complete occlusion (17,21). Enhancement of the vasa vasorum in the vessel wall and expansion of the lumen may be present (17,21). Inflammatory stranding of the perivenous fat may be seen with phlebitis (16). In cases of tumor thrombus secondary to invasion of the vein by hepatocellular carcinoma, enhancement of the thrombus can be seen on arterial-phase images and can help in distinguishing tumor thrombus from bland thrombus (21).

There are secondary changes in the portion of the liver supplied by the thrombosed portal vein. On scans obtained without intravenous contrast material, the affected lobe or segment of the liver is hypoattenuating because of depletion of glycogen content (17,21). On images obtained during the phase of hepatic artery dominance, a compensatory increase in arterial flow causes the liver to transiently appear hyperattenuating, which results in transient hepatic attenuation difference (21). With time, the thrombosed portal vein retracts and collateral veins dilate to produce the changes of cavernous transformation (Fig 5) (17). Alternatively, recanalization of the thrombosed portal vein may occur.

View larger version (154K): [in this window] [in a new window] [Download PPT slide]   Figure 5.   Cavernous transformation of the portal vein in a 47-year-old male liver transplantation candidate with cirrhosis secondary to hepatitis C. CT scan of the abdomen obtained with intravenous contrast material shows multiple collateral vessels (arrow) in the porta hepatis and the absence of the main portal vein, findings compatible with previous portal venous thrombosis. The stomach wall is thickened and enhanced due to gastric varices.

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 6a.   Varices secondary to portal hypertension in a 54-year-old female liver transplantation candidate with autoimmune hepatitis. (a) CT scan of the abdomen obtained with intravenous contrast material shows that the umbilical vein (arrow) is recanalized and dilated. (b) Coronal volume-rendered image shows the course of the umbilical vein (arrow).

View larger version (150K): [in this window] [in a new window] [Download PPT slide]   Figure 6b.   Varices secondary to portal hypertension in a 54-year-old female liver transplantation candidate with autoimmune hepatitis. (a) CT scan of the abdomen obtained with intravenous contrast material shows that the umbilical vein (arrow) is recanalized and dilated. (b) Coronal volume-rendered image shows the course of the umbilical vein (arrow).

CT angiography is an established technique for the evaluation of arterial anatomy, aneurysmal dilatation, and stenosis. Severe celiac artery stenosis can be shown at CT in liver transplantation candidates (25). The origin of the celiac artery can usually be assessed with axial images, since it is in the axial plane. However, the proximal part of the artery follows an oblique course, and the lumen cannot be adequately assessed with axial images. With volume-rendering three-dimensional technique, visualization of stenoses is not as dependent on vessel orientation (Fig 7) (25).Narrowing, mural thrombus, and poststenotic dilatation can be shown. In cases of compression of the median arcuate ligament, compression of the artery by the diaphragm is visible (23).

View larger version (125K): [in this window] [in a new window] [Download PPT slide]   Figure 7.   Evaluation for celiac artery stenosis in a 62-year-old female liver transplantation candidate with atherosclerotic disease and primary biliary cirrhosis. Sagittal volume-rendered image shows that the origin of the celiac artery is patent (arrow) and there is no evidence of stenosis.

Superior and Inferior Extent of the Transjugular Portosystemic Shunt
Some transplantation candidates will have undergone placement of a transjugular portosystemic shunt prior to transplantation. In these patients, the superior tip of the shunt is normally in the right hepatic vein and the inferior tip is in the right portal vein (Fig 8). Migration of the shunt and shunt-related stenosis are among the complications that can affect transplantation in 22%–34% of patients (11,26). If the shunt extends into the inferior vena cava, inflammatory change can occur in the vessel wall and can lead to scarring and narrowing of the cava (26). The scarred venous wall is resected at transplantation and may necessitate supradiaphragmatic dissection. Occasionally, the shunt tip can be in the right atrium, which further complicates removal of the native liver (27). Narrowing of the cava may also preclude living donor transplantation in which the recipient’s inferior vena cava is normally left intact.

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 8.   Appropriate location of the superior tip of a transjugular portosystemic shunt in a 50-year-old male liver transplantation candidate with cirrhosis secondary to hepatitis C. CT scan of the abdomen obtained with intravenous contrast material shows that the superior end of the shunt (arrow) is in the right hepatic vein, away from its junction with the inferior vena cava.

The location of the superior and inferior tips of the shunt can easily be determined from axial and three-dimensional CT images. The metallic stent walls are seen as curvilinear high-attenuation structures. With superior migration, the tip can lie in the intrahepatic or suprahepatic part of the inferior vena cava (Fig 9). In cases of low inferior shunt tips, the stent is seen in the extrahepatic part of the portal vein (Fig 10). The relationship of the stent tip to the splenomesenteric confluence can be shown on three-dimensional images.

View larger version (125K): [in this window] [in a new window] [Download PPT slide]   Figure 9a.   High superior tip of a transjugular portosystemic shunt in a 50-year-old male liver transplantation candidate with cirrhosis secondary to alcohol use. (a) CT scan of the abdomen obtained with intravenous contrast material shows that the superior tip of the shunt (arrow) extends into the inferior vena cava. (b) Coronal volume-rendered image also shows the superior migration of the shunt (arrow).

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 9b.   High superior tip of a transjugular portosystemic shunt in a 50-year-old male liver transplantation candidate with cirrhosis secondary to alcohol use. (a) CT scan of the abdomen obtained with intravenous contrast material shows that the superior tip of the shunt (arrow) extends into the inferior vena cava. (b) Coronal volume-rendered image also shows the superior migration of the shunt (arrow).

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 10a.   Low inferior tip of a transjugular portosystemic shunt in a 52-year-old man with cirrhosis. (a) CT scan of the abdomen obtained with intravenous contrast material shows the inferior tip of the shunt in the extrahepatic portion of the portal vein (arrow). (b) Coronal volume-rendered image also shows the tip of the shunt in the extrahepatic portion of the portal vein (arrow).

View larger version (109K): [in this window] [in a new window] [Download PPT slide]   Figure 10b.   Low inferior tip of a transjugular portosystemic shunt in a 52-year-old man with cirrhosis. (a) CT scan of the abdomen obtained with intravenous contrast material shows the inferior tip of the shunt in the extrahepatic portion of the portal vein (arrow). (b) Coronal volume-rendered image also shows the tip of the shunt in the extrahepatic portion of the portal vein (arrow).

	Evaluation in Living Donors

Top Abstract Introduction Surgical Technique: An Overview CT Protocol Evaluation in Recipients Evaluation in Living Donors Summary References

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 11.   Variant right hepatic arterial anatomy in a 53-year-old man. Coronal volume-rendered image of the abdomen enhanced with intravenous contrast material shows a replaced right hepatic artery (arrow) that arises from the superior mesenteric artery.

View larger version (139K): [in this window] [in a new window] [Download PPT slide]   Figure 12.   Variant left hepatic arterial anatomy in a 61-year-old man. Coronal volume-rendered image of the abdomen enhanced with intravenous contrast material shows a prominent branch (arrow) to the left lobe of the liver from the left gastric artery.

View larger version (145K): [in this window] [in a new window] [Download PPT slide]   Figure 13.   Small-caliber artery in a 28-year-old woman evaluated as a possible living donor for liver transplantation. Coronal volume-rendered image of the abdomen enhanced with intravenous contrast material shows the left hepatic artery (arrow) is small in caliber, measuring approximately 2.3 mm.

View larger version (154K): [in this window] [in a new window] [Download PPT slide]   Figure 14.   Origin of the medial-segment artery from the left hepatic artery in a 27-year-old man evaluated as a possible donor for living-related liver transplantation to a child. Axial volume-rendered image of the abdomen enhanced with intravenous contrast material shows that the medial segment of the left lobe of the liver is supplied by a branch (long arrow) from the left hepatic artery (short arrow).

View larger version (135K): [in this window] [in a new window] [Download PPT slide]   Figure 15.   Celiac artery stenosis that precluded donation in a 42-year-old man who underwent evaluation as a possible donor for living-related liver transplantation to an adult. Sagittal volume-rendered image of the abdomen enhanced with intravenous contrast material shows narrowing of the celiac artery at its origin from the aorta (arrow), a finding compatible with celiac artery stenosis. The subject, who also had a replaced right hepatic artery and a partially replaced left hepatic artery (not shown), was not considered to be a suitable donor because of his variant vascular anatomy and guidelines against surgery in a donor with a preexisting abnormality that may place him at theoretical risk of postsurgical hepatic artery thrombosis due to diminished flow.

Venous and Biliary Anatomy
The three main branches of the hepatic vein—the right, left, and middle veins—drain into the inferior vena cava (Fig 16). A variable number of branches can also drain part of the posterior segment of the right lobe of the liver directly into the inferior vena cava (Fig 17) (29). Such accessory right hepatic veins are estimated to occur in 6% of people (32). An accessory hepatic vein can cause increased bleeding if not recognized before surgery and may be necessary for venous drainage of the transplanted right lobe. If there are multiple veins, venoplasty is performed or each vein is anastomosed separately to the inferior vena cava.

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 16.   Normal hepatic venous drainage in a 38-year-old man who underwent evaluation as a possible donor for living-related liver transplantation. Axial volume-rendered image of the abdomen enhanced with intravenous contrast material shows that the hepatic vein from the posterior segment of the right lobe of the liver (short arrow) joins the main right hepatic vein (long arrow) to empty as one vessel into the inferior vena cava.

View larger version (127K): [in this window] [in a new window] [Download PPT slide]   Figure 17a.   Accessory right hepatic vein draining into the inferior vena cava in a 51-year-old man. (a) CT scan of the abdomen obtained with intravenous contrast material shows an accessory right hepatic vein in the posterior segment (open arrow). The main right hepatic vein is also visible (solid arrow). (b) Axial volume-rendered image shows separate drainage of the accessory right hepatic vein into the inferior vena cava (arrow).

View larger version (124K): [in this window] [in a new window] [Download PPT slide]   Figure 17b.   Accessory right hepatic vein draining into the inferior vena cava in a 51-year-old man. (a) CT scan of the abdomen obtained with intravenous contrast material shows an accessory right hepatic vein in the posterior segment (open arrow). The main right hepatic vein is also visible (solid arrow). (b) Axial volume-rendered image shows separate drainage of the accessory right hepatic vein into the inferior vena cava (arrow).

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 18.   Variant pattern of branching of the portal vein, which trifurcates at the hilum in a 38-year-old man who underwent evaluation as a possible donor for living-related liver transplantation. Coronal volume-rendered image of the abdomen enhanced with intravenous contrast material shows an early branch of the portal vein (long arrow) to the posterior segment of the right lobe of the liver. Branches to the left lobe (short arrow) and anterior segment of the right lobe are also visible.

Single right and left hepatic bile ducts join to form the common hepatic duct. In some patients, segmental ducts from the right or left lobes can join the common hepatic duct separately (29). Evaluation of the biliary tree is routinely performed in potential donors to delineate the anatomy. Since nondilated ducts are difficult to appreciate at CT without biliary enhancement, endoscopic retrograde cholangiopancreatography, magnetic resonance imaging, or CT cholangiography is necessary. CT cholangiography can be performed with oral administration of iopanoic acid and imaging after a 6- to 10-hour delay (33). In a pilot study of healthy volunteers and patients, biliary anatomy was better shown in the volunteers (33).

Liver Volumes
The volumes of potential donor livers determined with CT are matched with the volume needed by the recipient as calculated according to body surface area. The region of interest in the liver is outlined by hand on a workstation, and automated software is used to compute the liver volume. The volumes of the segment or lobe to be donated and of the remnant liver are calculated. A minimum of 40% of the normal liver volume is needed by the recipient (31). If the donor liver is too large, closure of the abdomen can be difficult and respiratory status may be compromised (Fig 19) (1). The donor volume is also used to ensure that a minimum of 35% of the liver is left in the donor (31).

View larger version (144K): [in this window] [in a new window] [Download PPT slide]   Figure 19.   Large left lobe of the liver in a 43-year-old woman who underwent evaluation as a possible donor for living-related liver transplantation to a child. Coronal volume-rendered image of the abdomen enhanced with intravenous contrast material shows that the left lateral segment of the liver (long arrow) is almost the same size as the right lobe of the liver. Enlargement of the liver was secondary to previously undetected liver disease, and the patient was not considered to be a donor candidate. The stomach (short arrow) is partially seen.

	Summary

Top Abstract Introduction Surgical Technique: An Overview CT Protocol Evaluation in Recipients Evaluation in Living Donors Summary References

 
Liver transplantation is a successful therapeutic option for patients with chronic liver disease and liver failure. Evaluation of recipients and donors is successfully performed with CT. In recipients, assessment of the liver parenchyma for malignancy, patency of the portal vein and celiac artery, and location of venous shunts is performed. In living donors, the liver parenchyma is evaluated for fatty change and liver volume is calculated. Arterial and venous anatomy is also mapped for surgical planning.

	References

Top Abstract Introduction Surgical Technique: An Overview CT Protocol Evaluation in Recipients Evaluation in Living Donors Summary References

 

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