**5. The role of laparoscopic approach**

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

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

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

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].

rows, in the sub-section dedicated to the role of IOUS in guiding hepatic resections.

**4.2. Hepatic metastases**

the personal archive of the authors).

78 Liver Research and Clinical Management

tumor surgery [41–46].

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,

MWA uses different parts of the electromagnetic spectrum) [90]. Although the elective treatment is by percutaneous approach, there are situations when both classical or laparoscopic

Intraoperative Ultrasound of the Liver: Actual Status and Indications

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Laparoscopic approach is particularly preferred on patients who are on the waiting list for liver transplantation or for those who cannot benefit from liver resection due to comorbidities, liver cirrhosis, or hepatic dysfunction due to chemotherapy, especially when percutaneous procedures are not possible [91–93]. Indications are subcapsular lesions located in the immediate vicinity of important structures (diaphragm, stomach, and gallbladder) or difficult to approach (caudal lobe). [84, 94–96]. Moreover, these ablation techniques can be combined with hepatic resections or can be performed serially after surgical resections, improving the oncological outcome and prognosis [97–99]. In the majority of cases treated by these procedures, IOUS is used as a guidance tool and for evaluation the efficacy of the treatment and

Multiple studies have demonstrated that IOUS-guided ablations are a safe and an effective treatment option that provides excellent local control of both primary and secondary hepatic tumor lesions [64, 94, 100–102]. Recent studies have also reported that intraoperative RFA has a local recurrence rate equivalent to that obtained from low-grade HCC surgery [11, 96] and

Localization of liver lesions is related to portal branches and suprahepatic veins, which are used to define segmental boundaries. Without the use of IOUS, it would probably be impossible to define correctly, anatomically, the hepatic segments and often the limits of the tumors,

Hepatic resections are known to be the standard treatment for malignant liver tumor formations, being the only procedure that provides oncological radicality [58]. Preservation of hepatic parenchyma should be a goal of the surgical team, especially in patients with cirrhotic liver, whose liver function and prognostic could be influenced by extensive resection. In these situations, IOUS plays an essential role because it allows the evaluation of the intrahepatic tumors, facilitating a limited but oncological liver resection. Thus, in modern hepatic surgery, whether HCC or colorectal liver metastases, the use of IOUS allows the realization of the so-called "radical but conservative surgery." Thus, obtaining continuous information on the relationship between liver lesions and intrahepatic bilio-vascular structures, the surgeon can guide his resection line, respecting the Glisson pedicles, and suprahepatic veins, with the ultimate goal of preserving as much functional hepatic parenchyma

IOUS is also a real help for anatomical resections. This technique involves the compression of segmental portal branches between the transducer and the operator's fingers, resulting in a transient ischemia of the target parenchyma. This area can be marked with the electrocautery,

especially due to the existence of multiple anatomical variants [13].

and then the resection is made along the demarcation line [105–110].

method are indicated.

appearance of complications [94].

colorectal hepatic metastases [64, 100].

**7. Guiding liver resections**

as possible [11, 12, 103, 104].

**Figure 4.** Laparoscopic ultrasound guided radiofrequency ablation of HCC on cirrhotic liver (intraoperative aspect, from the personal archive of the authors).

IVb, V, and VI). Direct visualization and LIOUS should be used to compensate for the impossibility of liver palpation in laparoscopic surgery [75, 76]. In the case of laparoscopically treated malignant lesions, it is important to mark by IOUS imaging the oncological resection margins, this way ensuring their tracing by minimally invasive approach. Furthermore, the completion of the treatment is possible using ablative techniques (radiofrequency, microwave). The laparoscopic approach finds its indications especially for higher-risk cirrhotic patients (altered hepatic markers, clotting disorders) with subcapsular neoplastic lesions (**Figure 4**).

With the evolution of technology and the experience of surgical teams, laparoscopic approaches to hepatectomies have become more and more used in centers of excellence. Several studies have shown that laparoscopic hepatectomy is a safe procedure and could have advantages over open surgery, translated by reduced blood loss and a shorter hospitalization stays [77, 78]. As for LIOUS, it should guarantee the same performance as the ultrasound used in conventional liver surgery. Although, LIOUS has been introduced since 1981, few studies have addressed this subject. Although reported to be a safe and accurate method [79], it is currently not routinely used in laparoscopic surgery [80], although the reliability of LIOUS in the staging of liver disease has been demonstrated to be similar to conventional IOUS [81]. Moreover, although many articles mention LIOUS as an important technique, few scientific papers described this technique [82–85].
