**4. IOUS of the liver: malignant tumor**

IOUS finds its usefulness in liver surgery for both primary and secondary malignant lesions facilitating the detection, characterization of lesions and guiding the surgical procedure [26, 27]. Most studies have evaluated the role of IOUS for treatment of hepatocarcinomas and hepatic metastases due to colorectal cancer, these pathologies being considered the most common liver malignant lesions. Intraoperative detection and local treatment of these lesions may have a major impact in choosing surgical strategy [28, 29].

#### **4.1. Hepatocarcinoma (HCC)**

from homogeneous to heterogeneous, with their edges becoming irregular. These features make them more difficult to differentiate from malignant tumor formations. When surgery is indicated, IOUS has the role to localize and visualize the relationships of the hemangioma with the intrahepatic structures. The surgeon can trace the hepatic resection line outside the hemangioma, minimizing hemorrhagic risk, and preserving the healthy hepatic parenchyma to its full potential. The CE-IOUS can be useful, capturing the contrast agent by the hemangioma being most of the time characteristic. Differentiation from malignant tumor formation becomes difficult for arterial hem-

For *focal nodular hyperplasia*, the central location of a fibrous scar is characteristic. This tumor appears as a well-defined lesions with variable size, usually unique, of solid consistency and inhomogeneous structure. Rarely, the central scar can be distinguished when using simple ultrasound, without contrast agent. When using CE-IOUS, in the arterial phase, there is a central filling followed by a complete capture in the venous phase. At this stage, the center of the tumor becomes hypoechoic. In the late phase, the tumor remains isogenic together with

*Hepatic adenoma* appears ecographically as a well-defined solid tumor lesion; it may have an inhomogeneous structure in the presence of intratumoral hemorrhage. Doppler ultrasound does not detect a vascular signal. When using CE-IOUS, in the arterial phase, there is a centripetal and inconsistent capture; in the venous phase, a moderate washout may be noted. In

Differentiation between focal nodular hyperplasia and hepatic adenoma is important for establishing the therapeutic indication, surgery being indicated for large adenomas, due to

Because sometimes it is difficult to make a benign-malignant US differentiation, intraoperatory, when the situation imposes, might by necessary to make a bioptic puncture for establishing a correct diagnosis [20]. IOUS has an important guiding role, especially in the case of

*Simple hepatic cysts (biliary cysts)* are benign tumors with no malignant potential, usually asymptomatic, that can be easily diagnosed with ultrasound imaging. They are described by ultrasound as well-defined lesions with very thin walls, no Doppler signal, anechoic, with transonic content due to the liquid composition. Simple hepatic cysts have therapeutic indications only when they become symptomatic, often due to symptoms related to the mass effect

Percutaneous ultrasound guided treatment with cyst evacuation is often possible, but is followed by an increased risk of relapse, with the rebound of collection. In this idea, the laparoscopic surgical resection of the cystic dome is indicated. This technique is easy if the lesions are located superficially, in segments II, III, IVB, V, VI (after Couinaud) [23]. The lesions local-

Depending on the evolutionary stage, *hydatid cysts* may appear as single or multiple lesions, anechoic, with membranes and sediment inside, with thin or calcified walls. They may be multilocular or may contain multiple fluid compartments (daughter vesicles). IOUS helps the surgeon in finding the cysts and in some situations it can detect bile duct communication. These lesions

ized intraparenchymatous can be approached safely only when using IOUS [24].

the hepatic parenchyma, which strengthens the diagnosis of benign lesion [21].

the risk of rupture and hemorrhage as well as due to its malignant potential.

lesions located in the depth of the liver parenchyma, hard to reach when palpating.

the late phase, the appearance is isoechoic or hyperechoic [21].

they have on neighboring structures.

angiomas or for those with arterio-venous shunts [21].

76 Liver Research and Clinical Management

HCC is the most common primary malignancy in the liver, and is frequently associated with cirrhosis [30, 31].

Ecographically, this tumor has the appearance of a solid tumor with irregular contours, heterogeneous, uni-, or multilocular ("encephaloid form"). Typically, it invades the liver vessels, primarily the portal branches, but also the suprahepatic veins. Doppler screening usually highlights a high-speed arterial flow. Vessel distribution is irregular, disordered. CE-US shows hypercaptation in the arterial phase with a specific "washout" of contrast substance in the venous phase. In the late phase, the tumor appears as hypoechoic. This behavior is usually described in tumor nodules larger than 2 cm [21].

In the case of HCC, IOUS is superior in detecting lesions measuring less than 1 cm, preoperative MRI having a lower sensitivity and specificity for these lesions [11, 32]. It has also been shown in several studies that CE-IOUS can modify in 19–29% of the cases the initial treatment plan [33, 34]. CE-IOUS finds its usefulness especially in cirrhotic patients when it comes to differential diagnosis between malignant lesions and regenerative nodules [29, 35]. It has been demonstrated that neoangiogenesis of tumor nodules is a specific criteria for distinguishing hepatocarcinomas from dysplastic or regenerative nodules [35].

CE-IOUS has a sensitivity of 100%, a specificity between 69 and 100% and can modify the surgical strategy in up to 79% of patients [36–38], most frequently by detecting new lesions. The literature emphasizes that the filling pattern of the contrast agent in nodules found by IOUS can guide surgical resection [36]. It has also been shown that the vascular pattern of HCC visualized by using CE-IOUS has been associated with the expression of some genetic profiles, suggesting that CE-IOUS images can be used as an indicator for predicting prognosis of patients [39].

During hepatic resection, which is the standard treatment for HCC, particular attention should be paid in preserving as much hepatic parenchyma as we can, the remaining hepatic volume being an important prognostic factor for the short outcome [37, 39, 40]. Thus, local resection of the tumor formation or its ablation under IOUS guidance may be chosen to minimize the

Several studies in the literature have shown that after the surgical treatment of the primary tumor, the ultrasound of metastasis after colorectal cancer can be correlated with prognosis. Thus, Gruenberger et al. [52] demonstrated that in patients with hyperechoic ultrasound liver metastases, survival is longer than in those with the hypoechoic aspect of the lesions. This suggests that the role of IOUS is more than a diagnostic one and can be useful in establishing prognosis [53].

Intraoperative Ultrasound of the Liver: Actual Status and Indications

http://dx.doi.org/10.5772/intechopen.73856

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The CE-IOUS applied for colorectal liver metastases has an 96% accuracy, in contrast to 74 and 79%, percentages associated with pre-operative CT and MRI [34, 54]. The fact that undetected preoperative liver metastases represent the main cause of recurrent neoplasia [55] highlights the important role that IOUS has in the management of patients diagnosed with colorectal

Chemotherapy is an important, standardized element in regard with the adjuvant and neoadjuvant therapy in colorectal cancer patients. [57, 58] Regarding hepatic metastases, good results of cytostatic treatment mean either stagnation or regression of these lesions [59, 60]. A particular situation is when liver metastases are no longer visible in CT and/or MRI performed after chemotherapy. Literature indicates that the complete, real response is found in up to 66% of cases [61, 62]. For the rest of the cases (34%), chemotherapy can affect the echogenity of the metastases making them difficult to be identified with preoperative imaging (CT, MRI, even IOUS) [13, 33]. In these situations, CE-IOUS allows the surgeon to check areas where hepatic lesions have been described before chemotherapy [11]. The role of this technique is highlighted in many studies that have shown that only be confirmation given by the CE-IOUS in regard with the lack of lesions can be associated with a complete therapeutic response [59, 62].

Resection or ablation of all lesions is the gold standard in the treatment of colorectal liver metastases [63]. Even in patients with unresectable metastases, local ablation or combination between ablation and surgical resection of the lesions has been shown to be able to locally control the disease [64]. It is obvious that IOUS plays a major role in liver surgery for the

The laparoscopic approach and minimally invasive surgery have more and more indications and thus the role of IOUS in laparoscopic surgery has become increasingly important. Of course, laparoscopic surgery has some disadvantages in assessing the liver because the surgeon loses the advantage of palpating the structures and lesions. IOUS manages to compensate for most of these laparoscopic minuses by providing intraoperative high utility imaging with greater sensitivity in detecting liver lesions than most preoperative imaging techniques [65–69]. Intraoperative laparoscopic ultrasound (LIOUS) has a sensitivity and specificity similar to that in open surgery [69]. Several authors have suggested routine use of LIOUS in laparoscopic colorectal surgery [70] and prior to planned laparotomies for liver resections [71]. In cases where hepatic disease is known, with the help of LIOUS data, around 64% of cases could be exempted from laparotomy [71, 72]. The success of the laparoscopic approach depends primarily on the location of the lesions [73, 74]. Guiding surgical maneuvers by the use of LIOUS is possible especially in superficial tumors on the left lobe or on the anterior segments of the right lobe (hepatic segments II, III,

cancer. This is why routine IOUS is recommended in these patients [56].

detection and localization of metastatic lesions [28].

**5. The role of laparoscopic approach**

**Figure 3.** Anatomical resection: ischemic delimitation of sixth and seventh liver segments (intraoperative aspect, from the personal archive of the authors).

volume of resected liver parenchyma, respecting the oncological resection margin. Also, in order to minimize the risk of postoperative complications (hemorrhage, necrosis of the liver parenchyma) and remote relapse (by satellite micrometastases, specific for HCC), the use of IOUS is vital in guiding anatomical resections. These involve the ultrasound identification of vascular pedicles corresponding to the affected hepatic segments and through various associated maneuvers (digital compression, injection of contrast agents) an exact delimitation of the targeted resection area can be obtained (**Figure 3**). More details will be given in the following rows, in the sub-section dedicated to the role of IOUS in guiding hepatic resections.

#### **4.2. Hepatic metastases**

Despite significant advances in preoperative staging diagnostic procedures (conventional CE-US, multi-sliced CT, CE-MRI, and PET-CT), studies have shown that 10–30% of the patients with colo-rectal cancer remain with undiagnosed hepatic metastases during primary tumor surgery [41–46].

In this respect, IOUS and CE-IOUS have a special role in completing the diagnosis, in addition to the liver's palpation technique. IOUS is considered the "gold standard" in open surgery for colorectal cancer since 1980, being able to detect liver metastases that cannot be palpated intraoperatively and that have not been visualized with preoperative imaging techniques [8, 47–50].

Liver metastases have a non-characteristic echographic appearance, being circumscribed lesions with imprecise or halo delineation, with a homogeneous or heterogeneous pattern. They may be solitary (usually liver metastases from colonic neoplasms) or multiple. Their echogenicity is variable. When they are large, they can compress the bile ducts (which may appear to be dilated) and the liver vessels. As for their vascularization, they may be hypovascular (in gastric, colon, pancreatic, or ovarian cancers) with hypoechoic pattern in arterial phase and similar in the venous and late phases or hypervascular (neuroendocrine tumors, malignant melanomas, sarcomas, renal tumors, breast, or thyroids), with a hyperechoic appearance during the arterial phase, with wash out during the venous phase and hypoechoic pattern at about 30 s after the injection of the contrast substance [51].

Several studies in the literature have shown that after the surgical treatment of the primary tumor, the ultrasound of metastasis after colorectal cancer can be correlated with prognosis. Thus, Gruenberger et al. [52] demonstrated that in patients with hyperechoic ultrasound liver metastases, survival is longer than in those with the hypoechoic aspect of the lesions. This suggests that the role of IOUS is more than a diagnostic one and can be useful in establishing prognosis [53].

The CE-IOUS applied for colorectal liver metastases has an 96% accuracy, in contrast to 74 and 79%, percentages associated with pre-operative CT and MRI [34, 54]. The fact that undetected preoperative liver metastases represent the main cause of recurrent neoplasia [55] highlights the important role that IOUS has in the management of patients diagnosed with colorectal cancer. This is why routine IOUS is recommended in these patients [56].

Chemotherapy is an important, standardized element in regard with the adjuvant and neoadjuvant therapy in colorectal cancer patients. [57, 58] Regarding hepatic metastases, good results of cytostatic treatment mean either stagnation or regression of these lesions [59, 60]. A particular situation is when liver metastases are no longer visible in CT and/or MRI performed after chemotherapy. Literature indicates that the complete, real response is found in up to 66% of cases [61, 62]. For the rest of the cases (34%), chemotherapy can affect the echogenity of the metastases making them difficult to be identified with preoperative imaging (CT, MRI, even IOUS) [13, 33]. In these situations, CE-IOUS allows the surgeon to check areas where hepatic lesions have been described before chemotherapy [11]. The role of this technique is highlighted in many studies that have shown that only be confirmation given by the CE-IOUS in regard with the lack of lesions can be associated with a complete therapeutic response [59, 62].

Resection or ablation of all lesions is the gold standard in the treatment of colorectal liver metastases [63]. Even in patients with unresectable metastases, local ablation or combination between ablation and surgical resection of the lesions has been shown to be able to locally control the disease [64]. It is obvious that IOUS plays a major role in liver surgery for the detection and localization of metastatic lesions [28].
