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DOI: 10.1148/rg.264055120
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Intraoperative US of the Liver: Techniques and Clinical Applications1

Jonathan B. Kruskal, MD, PhD and Robert A. Kane, MD, FACR

1 From the Abdominal Imaging Section, Department of Radiology, Clinical Center 302B, Beth Israel Deaconess Medical Center, 1 Deaconess Rd, Boston MA 02215. Presented as an education exhibit at the 2004 RSNA Annual Meeting. Received May 13, 2005; revision requested June 20; revision received and accepted August 9. Authors have no financial relationships to disclose.

Figure 1
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  		Figure 1.  Photograph shows the position in which the specially designed intraoperative transducer should be held, cradled between the fingers and resting against the palm of the hand. In this way, not only can easily exposed segments of the liver be imaged but the transducer also can access more challenging locations such as the high dome and the right lateral margin.

 

Figure 2
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  		Figure 2a.  Intraoperative anatomy and scanning technique. (a) Diagram shows the Couinaud classification system for liver segmentation. This is the system most commonly used by hepatic surgeons and other physicians to describe the hepatic anatomy. (b) Photograph and superimposed white line show a useful method for scanning of the entire liver during an intraoperative US survey for metastases, with multiple overlapping sagittal sweeps performed while the transducer is held in a transverse position.

 

Figure 2
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  		Figure 2b.  Intraoperative anatomy and scanning technique. (a) Diagram shows the Couinaud classification system for liver segmentation. This is the system most commonly used by hepatic surgeons and other physicians to describe the hepatic anatomy. (b) Photograph and superimposed white line show a useful method for scanning of the entire liver during an intraoperative US survey for metastases, with multiple overlapping sagittal sweeps performed while the transducer is held in a transverse position.

 

Figure 3
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  		Figure 3a.  Water standoff used for better characterization of superficial lesions in the near field of the liver. (a) US image shows a small hypoechoic lesion (arrow) just below the liver capsule. (b) US image obtained after bathing the liver in saline solution for improved acoustic coupling demonstrates a small, superficial, simple cyst (arrow).

 

Figure 3
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  		Figure 3b.  Water standoff used for better characterization of superficial lesions in the near field of the liver. (a) US image shows a small hypoechoic lesion (arrow) just below the liver capsule. (b) US image obtained after bathing the liver in saline solution for improved acoustic coupling demonstrates a small, superficial, simple cyst (arrow).

 

Figure 4
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  		Figure 4.  Replaced right hepatic artery. Intraoperative color Doppler US image shows a replaced artery (arrow) that arises from the superior mesenteric artery (arrowhead) and courses between the portal vein (PV), which is anterior to it, and the more posteriorly located vena cava (IVC).

 

Figure 5
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  		Figure 5a.  Replaced left hepatic artery. (a) Intraoperative gray-scale US image shows a replaced artery that courses through the ligamentum venosum (arrow), which is located anterior to the caudate lobe and vena cava (IVC). (b) Intraoperative color Doppler US image demonstrates the presence of flow through the replaced vessel, which arises from the left hepatic artery. (c) Intraoperative color Doppler US image shows not only the replaced artery (small arrow) that courses through the echogenic ligamentum venosum but also a potentially significant collateral vessel (large arrow) that connects the portal vein with the vena cava in the caudate lobe. The depiction of such vessels is important for the planning of any surgical resection in this anatomic region.

 

Figure 5
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  		Figure 5b.  Replaced left hepatic artery. (a) Intraoperative gray-scale US image shows a replaced artery that courses through the ligamentum venosum (arrow), which is located anterior to the caudate lobe and vena cava (IVC). (b) Intraoperative color Doppler US image demonstrates the presence of flow through the replaced vessel, which arises from the left hepatic artery. (c) Intraoperative color Doppler US image shows not only the replaced artery (small arrow) that courses through the echogenic ligamentum venosum but also a potentially significant collateral vessel (large arrow) that connects the portal vein with the vena cava in the caudate lobe. The depiction of such vessels is important for the planning of any surgical resection in this anatomic region.

 

Figure 5
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  		Figure 5c.  Replaced left hepatic artery. (a) Intraoperative gray-scale US image shows a replaced artery that courses through the ligamentum venosum (arrow), which is located anterior to the caudate lobe and vena cava (IVC). (b) Intraoperative color Doppler US image demonstrates the presence of flow through the replaced vessel, which arises from the left hepatic artery. (c) Intraoperative color Doppler US image shows not only the replaced artery (small arrow) that courses through the echogenic ligamentum venosum but also a potentially significant collateral vessel (large arrow) that connects the portal vein with the vena cava in the caudate lobe. The depiction of such vessels is important for the planning of any surgical resection in this anatomic region.

 

Figure 6
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  		Figure 6.  Colorectal cancer metastases in the liver. Intraoperative US image of segments I and II of the liver shows an ill-defined infiltrative metastasis located primarily in the caudate lobe. The tumor has obliterated the normally echogenic ligamentum venosum (arrow).

 

Figure 7
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  		Figure 7.  Colorectal cancer metastases in the liver. Intraoperative gray-scale US image shows an ill-defined colorectal cancer metastasis (large arrow) that has grown into and occludes the right hepatic vein (RHV), as well as a small superior accessory right hepatic vein (small arrows) that drains into the vena cava. The identification of the accessory vein was important for surgical planning of metastasectomy in this patient.

 

Figure 8
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  		Figure 8.  Focal fatty replacement. Intraoperative US image demonstrates a well-circumscribed area of increased echogenicity at the bifurcation of the main portal vein (large arrows). Note the small vessel that courses through the center of the fatty region (small arrow). In the intraoperative setting, areas of focal fatty replacement are often compressible.

 

Figure 9
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  		Figure 9a.  Focal fatty sparing. (a) Intraoperative US image depicts an ill-defined hypoechoic region (arrows) that abuts the right portal vein in a patient with diffuse fatty replacement of the liver. (b) Intraoperative US image demonstrates peripheral subcapsular hypoechoic regions (arrows) consistent with focal fatty sparing. Peripheral regions of fatty sparing or replacement should not produce any bulging in the liver contours.

 

Figure 9
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  		Figure 9b.  Focal fatty sparing. (a) Intraoperative US image depicts an ill-defined hypoechoic region (arrows) that abuts the right portal vein in a patient with diffuse fatty replacement of the liver. (b) Intraoperative US image demonstrates peripheral subcapsular hypoechoic regions (arrows) consistent with focal fatty sparing. Peripheral regions of fatty sparing or replacement should not produce any bulging in the liver contours.

 

Figure 10
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  		Figure 10.  Hepatocellular carcinoma and focal fatty sparing. Intraoperative image obtained during a US-guided metastasectomy demonstrates a hypoechoic hepatocellular carcinoma (arrow) adjacent to a peripheral region of focal fatty sparing (arrowhead). Note the adjacent echogenic region consistent with steatosis.

 

Figure 11
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  		Figure 11.  Colorectal cancer metastasis in the liver. Intraoperative US image demonstrates a lobular, hypoechoic, solitary metastasis (small arrows) that produces bulging of the liver contours (large arrows).

 

Figure 12
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  		Figure 12.  Angiomyolipoma. Intraoperative US image shows an isolated lesion in segment VI of the liver (arrows). The fat component is echogenic and easily visible, but other components of the lesion are less easily seen in the intraoperative setting.

 

Figure 13
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  		Figure 13a.  Artifacts from sonication of the liver surface. (a) Intraoperative image demonstrates small echogenic bubbles (arrow) that entered the liver parenchyma at the cut surface during segmentectomy with high-frequency sonication. (b, c) Intraoperative images show intrahepatic gas bubbles in hepatic segments remote from the site of sonication (b) and gas bubbles localized to the perisinusoidal space around a tumor (arrow in c).

 

Figure 13
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  		Figure 13b.  Artifacts from sonication of the liver surface. (a) Intraoperative image demonstrates small echogenic bubbles (arrow) that entered the liver parenchyma at the cut surface during segmentectomy with high-frequency sonication. (b, c) Intraoperative images show intrahepatic gas bubbles in hepatic segments remote from the site of sonication (b) and gas bubbles localized to the perisinusoidal space around a tumor (arrow in c).

 

Figure 13
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  		Figure 13c.  Artifacts from sonication of the liver surface. (a) Intraoperative image demonstrates small echogenic bubbles (arrow) that entered the liver parenchyma at the cut surface during segmentectomy with high-frequency sonication. (b, c) Intraoperative images show intrahepatic gas bubbles in hepatic segments remote from the site of sonication (b) and gas bubbles localized to the perisinusoidal space around a tumor (arrow in c).

 

Figure 14
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  		Figure 14a.  Focal nodular hyperplasia. (a) Intraoperative image demonstrates a large nodular lesion between the right (RHV) and middle hepatic veins (MHV). Note the homogeneous nature of this benign tumor, which effaces the vessels but has not occluded them. (b) Intraoperative image from repeat US of the liver after attempted resection of the mass shows the echogenic cut surface of the liver (arrows) and an adjacent isoechoic area of residual tumor between the right (RHV) and middle (MHV) hepatic veins.

 

Figure 14
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  		Figure 14b.  Focal nodular hyperplasia. (a) Intraoperative image demonstrates a large nodular lesion between the right (RHV) and middle hepatic veins (MHV). Note the homogeneous nature of this benign tumor, which effaces the vessels but has not occluded them. (b) Intraoperative image from repeat US of the liver after attempted resection of the mass shows the echogenic cut surface of the liver (arrows) and an adjacent isoechoic area of residual tumor between the right (RHV) and middle (MHV) hepatic veins.

 

Figure 15
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  		Figure 15a.  Cautery artifact. (a) Intraoperative image in a patient with hepatocellular carcinoma and a thrombus in the left portal vein (arrow) shows curvilinear echogenic bands in the far field, artifacts of cautery performed during image acquisition. (b) Intraoperative image in another patient with infiltrative hepatocellular carcinoma shows more linear bandlike echogenic artifacts that radiate from the transducer location.

 

Figure 15
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  		Figure 15b.  Cautery artifact. (a) Intraoperative image in a patient with hepatocellular carcinoma and a thrombus in the left portal vein (arrow) shows curvilinear echogenic bands in the far field, artifacts of cautery performed during image acquisition. (b) Intraoperative image in another patient with infiltrative hepatocellular carcinoma shows more linear bandlike echogenic artifacts that radiate from the transducer location.

 

Figure 16
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  		Figure 16.  Intraoperative image shows an accumulation of air anterior to the inferior vena cava (arrow), a finding that mimics air within the vena cava.

 

Figure 17
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  		Figure 17.  Intraoperative image obtained immediately after cholecystectomy and prior to a hepatic lobar resection shows a linear echogenic band with posterior acoustic shadowing, an artifact caused by air in the gallbladder fossa.

 

Figure 18
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  		Figure 18.  Intraoperative image shows acoustic shadowing that obscures structures adjacent to the liver. The artifact was caused by surgical packing material placed around the liver surface or in the surgical bed.

 

Figure 19
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  		Figure 19.  Acoustic shadowing produced by palpation of the posterior liver surface. Intraoperative image of the right lobe of the liver demonstrates acoustic shadowing caused by two echogenic foci in the far field, artifacts that resemble colorectal cancer metastases.

 

Figure 20
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  		Figure 20a.  Mucinous colorectal cancer metastases. (a) Intraoperative image demonstrates acoustic shadowing produced by a small, superficial colorectal cancer metastasis. Note the thin rim of normal liver tissue superficial to this metastasis. (b) Intraoperative image obtained during US-guided hepatic metastasectomy shows acoustic shadowing produced by cautery of the liver capsule (large arrow). Cautery was performed lateral to a large, solitary metastasis (small arrows) to mark the planned surgical margin of approximately 1 cm.

 

Figure 20
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  		Figure 20b.  Mucinous colorectal cancer metastases. (a) Intraoperative image demonstrates acoustic shadowing produced by a small, superficial colorectal cancer metastasis. Note the thin rim of normal liver tissue superficial to this metastasis. (b) Intraoperative image obtained during US-guided hepatic metastasectomy shows acoustic shadowing produced by cautery of the liver capsule (large arrow). Cautery was performed lateral to a large, solitary metastasis (small arrows) to mark the planned surgical margin of approximately 1 cm.

 

Figure 21
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  		Figure 21a.  Colorectal cancer metastases. (a) Intraoperative image demonstrates a small, hypoechoic colorectal cancer metastasis (arrow) in segment VI of the liver. Note the adjacent kidney, which, in the intraoperative setting, may have an echotexture similar to that of the liver. (b) Intraoperative image shows a well-circumscribed echogenic colorectal cancer metastasis (arrow) in a superficial location in the far field.

 

Figure 21
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  		Figure 21b.  Colorectal cancer metastases. (a) Intraoperative image demonstrates a small, hypoechoic colorectal cancer metastasis (arrow) in segment VI of the liver. Note the adjacent kidney, which, in the intraoperative setting, may have an echotexture similar to that of the liver. (b) Intraoperative image shows a well-circumscribed echogenic colorectal cancer metastasis (arrow) in a superficial location in the far field.

 

Figure 22
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  		Figure 22.  Mucinous colorectal cancer metastasis adjacent to the portal vein. Intraoperative image demonstrates acoustic shadowing produced by a small colorectal cancer metastasis (large arrow). Note that the adjacent portal vein (small arrows), although it has a somewhat similar echogenic appearance due to collagen within its wall, is not accompanied by acoustic shadowing.

 

Figure 23
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  		Figure 23a.  Hepatic hemangiomas. (a) Intraoperative image shows a large, solitary hemangioma (large arrows) that was found incidentally at US during gastric surgery. In the intraoperative setting, such lesions are palpably soft, and on Doppler US images they do not demonstrate more flow than that in the adjacent liver parenchyma. The morphologic features of hepatic hemangiomas may vary at intraoperative US: The lesion in this case effaces the right hepatic vein (small arrows) but has not caused occlusion or thrombus formation. (b, c) Intraoperative images show small (arrow in b) and larger (arrows in c) fibrosed hemangiomas that differ in appearance from their more common, homogeneously echogenic counterparts.

 

Figure 23
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  		Figure 23b.  Hepatic hemangiomas. (a) Intraoperative image shows a large, solitary hemangioma (large arrows) that was found incidentally at US during gastric surgery. In the intraoperative setting, such lesions are palpably soft, and on Doppler US images they do not demonstrate more flow than that in the adjacent liver parenchyma. The morphologic features of hepatic hemangiomas may vary at intraoperative US: The lesion in this case effaces the right hepatic vein (small arrows) but has not caused occlusion or thrombus formation. (b, c) Intraoperative images show small (arrow in b) and larger (arrows in c) fibrosed hemangiomas that differ in appearance from their more common, homogeneously echogenic counterparts.

 

Figure 23
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  		Figure 23c.  Hepatic hemangiomas. (a) Intraoperative image shows a large, solitary hemangioma (large arrows) that was found incidentally at US during gastric surgery. In the intraoperative setting, such lesions are palpably soft, and on Doppler US images they do not demonstrate more flow than that in the adjacent liver parenchyma. The morphologic features of hepatic hemangiomas may vary at intraoperative US: The lesion in this case effaces the right hepatic vein (small arrows) but has not caused occlusion or thrombus formation. (b, c) Intraoperative images show small (arrow in b) and larger (arrows in c) fibrosed hemangiomas that differ in appearance from their more common, homogeneously echogenic counterparts.

 

Figure 24
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  		Figure 24.  Targetlike carcinoid metastasis. Intraoperative image shows a targetlike lesion (arrows) with a central hyperechoic region. Several types of hepatic tumors may have this appearance—most commonly, colorectal cancer metastases, in which the central region of echogenicity represents calcification, and carcinoid metastases.

 

Figure 25
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  		Figure 25.  Mucinous colorectal cancer metastasis. Intraoperative image shows an isolated metastasis with central mucinous calcifications that produce acoustic shadowing. Note the proximity of the tumor to the vena cava (IVC), middle hepatic vein (MHV), and right hepatic vein (RHV).

 

Figure 26
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  		Figure 26.  Mucinous colorectal cancer metastasis. Intraoperative image shows a metastasis with internal calcifications (arrows) that produce acoustic shadowing, which obscures the caudate lobe posteriorly. In this situation, the obscured segments of the liver should be imaged from other angles.

 

Figure 27
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  		Figure 27.  Hepatocellular carcinoma and hemangioma in a 51-year-old man. Intraoperative color Doppler image demonstrates a predominantly hypoechoic mass in the high dome in segment VII of the liver and an adjacent small echogenic hemangioma (arrow). Note the absence of flow in the mass.

 

Figure 28
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  		Figure 28.  Vascular invasion by a colorectal cancer metastasis. Intraoperative image demonstrates invasion of the right hepatic vein (large arrow) and the vena cava (small arrow) by a colorectal cancer metastasis (CRC). Accurate intraoperative US localization of this lesion in segment VII of the liver facilitated its surgical resection.

 

Figure 29
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  		Figure 29.  Isolated colorectal metastasis in the caudate lobe. Intraoperative image demonstrates an almost isoechoic lesion in the caudate lobe (arrows), as well as an echogenic accumulation of air in the medial portion of the ligamentum teres, a normal finding in the intraoperative setting.

 

Figure 30
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  		Figure 30.  Superficial colorectal cancer metastasis. Intraoperative image depicts a hypoechoic lesion (arrows) superficial to the right portal vein (RPV) and separated from it by a margin of normal tissue, an important finding for surgical planning. The round area of echogenicity lateral to the tumor was caused by cautery of the liver capsule to mark the surgical resection margin.

 

Figure 31
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  		Figure 31.  Periductal cholangiocarcinoma. Intraoperative color Doppler US image depicts the precise relationship between the periductal cholangiocarcinoma (large arrow) and the right hepatic duct (small arrows), information that helped spare the right ductal system during resection of the left lobe of the liver.

 

Figure 32
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  		Figure 32.  Thrombus. Intraoperative color Doppler flow image obtained during US-guided metastasectomy in a patient with hepatocellular carcinoma shows a thrombus in the left portal vein (arrows).

 

Figure 33
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  		Figure 33.  Vascular invasion by metastasis. Intraoperative US image demonstrates a colorectal cancer metastasis (arrow) that has invaded the distal portion of the right hepatic vein (RHV) at its confluence with the adjacent vena cava (IVC). In this setting, if resection is performed, segment VII (posterior to the right hepatic vein) and segment VIII (anterior to the right hepatic vein) of the liver are likely to be resected.

 

Figure 34
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  		Figure 34.  Image obtained during tumor thrombectomy shows expansion of the retrohepatic vena cava by an echogenic renal cell carcinoma (arrows) that originated in the left kidney.

 

Figure 35
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  		Figure 35.  Intraoperative image depicts a large echogenic hemangioma (large arrows) that has displaced and effaced the right hepatic vein (small arrows) but has not occluded it.

 

Figure 36
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  		Figure 36.  Image obtained for planning of a living-related split-liver transplantation shows the relatively avascular plane between the right and left lobes of the liver (between segments VII and VIII); the insertion sites of the middle (MHV) and right hepatic veins (RHV) into the vena cava (IVC); and the location and size of the veins that drain into the middle hepatic vein from segments V, VII, and VIII (arrows).

 

Figure 37
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  		Figure 37.  Intraoperative US image shows a thrombus located between the confluence of the middle and right hepatic veins (small arrows) anteriorly and the recipient vena cava (large arrow) posteriorly, a finding that is not unusual in an implanted cadaveric liver. Extension of the thrombus into adjacent veins was ruled out before thrombectomy was performed.

 




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