**4. Preoperative radiologic evaluation: the target parameters**

To plan the surgical treatment, the number, the size and the location of metastases must be detected [1]. The number of affected segments, the relations between metastases and arteries, veins and bile ducts as well as the size of remnant liver must be ascertained as well [18]. The anatomical variations of bile ducts as well as arterial and portal blood vessels must be established. CT or MRI can be used for these purposes. Although similar efficacy of both methods has been shown regarding vascular anatomic evaluation, CT can yield better contrast [1].

Diagnostic problems can be associated with identification of small lesions, imaging of meta‐ stases on the background of liver fibrosis, steatosis or sinusoidal congestion due to preceding chemotherapy (or other reasons) and detailed characteristics of deep metastasis that necessi‐ tates careful planning of surgical approach and exact data on the involvement of anatomical structures. Occasionally, differential diagnosis with benign lesions can be complicated. The presence and extent of extrahepatic disease must be estimated [18].

Software-based three-dimensional CT volumetrics is used to calculate the volume of the remnant and total liver volumes excluding nonfunctional spaces as tumours, cysts and ablation cavities. The remnant liver volume is expressed as a proportion of the preoperative total liver volume. The minimal volume of remnant liver has not been established by exact experimental studies therefore the described desirable values differ slightly. The remnant liver volume after the operation is expected to be 25–30% in young patients with normal liver parenchyma and 40% in cirrhotic patients [4, 18]. In a consensus statement, remnant liver volume is recom‐ mended to be at least 20% for patients with normal extratumoural liver tissue, 30% for patients having chemotherapy-induced liver injury and 40% in cirrhotic patients [17, 38–40]. As metastatic tumour is spreading systemically and recurs in most patients, higher preserved proportion of liver parenchyma provides more options for repeated future surgery if neces‐ sary. The risk factors for postoperative liver dysfunction due to insufficient remnant include older age, liver fibrosis, cirrhosis and preoperative chemotherapy. Except liver cirrhosis, these factors are frequent as many patients with CRC liver metastasis are elderly and have received chemotherapy [4]. To estimate the compromised liver function more exactly, functional tests are helpful. The liver function is reflected by albumin level, hemostasis, bilirubin level, lidocaine conversion test or clearance of indocyanine green [18].

In the early studies, liver US was considered effective in the follow-up after surgical treatment of colorectal cancer metastases as it disclosed all the resectable cancer metastases as it disclosed all the resectable with thoracic X-ray [36]. However, more recent data evidence that transab‐ dominal US has limited sensitivity in the diagnostics of CRC liver metastases: 50–75% [17]. Despite the serious shortcoming, US still can be used for screening purposes by experienced specialist who is aware of these limitations and will combine US by more sensitive methods of radiologic diagnostics. Intravenous contrast-enhanced US imaging using microbubbles to contrast blood increases the sensitivity of US by 20% [17, 19] and exceeds the sensitivity of CT, especially for small lesions [17]. Contrast-enhanced US affords diagnostic benefit in 13.7% patients with liver mass lesions [19]. The increased sensitivity of contrast-enhanced US in detection of tumours is explained by the vascularisation pattern and the phagocytosis of contrasting microbubbles by Kupffer cells that are present in liver parenchyma but absent in liver tumours. Thus, CRC metastases would be an adequate object for contrast US. The tumours are hypoechoic. The sensitivity and specificity of US and contrast-enhanced US in diagnosing malignant liver tumours is around 58.8% and 50.7% for US versus 68.7–90% and 67–88% for the contrast-enhanced modality. Deep lesions, small metastases and liver steatosis are known limiting factors. Colorectal cancer metastases may occasionally be hyperechogenic and lack hypoechoic structure on contrast-enhanced US embarrassing differential diagnosis with

Hepatic lesions can be missed even by combined radiologic investigation, including US, CT and MRI. The proportion of such lesions can be as high as 30% [19]. Intraoperatively, US can be applied. The sensitivity of intraoperative imaging is again enhanced by contrast US [37].

To plan the surgical treatment, the number, the size and the location of metastases must be detected [1]. The number of affected segments, the relations between metastases and arteries, veins and bile ducts as well as the size of remnant liver must be ascertained as well [18]. The anatomical variations of bile ducts as well as arterial and portal blood vessels must be established. CT or MRI can be used for these purposes. Although similar efficacy of both methods has been shown regarding vascular anatomic evaluation, CT can yield better contrast

Diagnostic problems can be associated with identification of small lesions, imaging of meta‐ stases on the background of liver fibrosis, steatosis or sinusoidal congestion due to preceding chemotherapy (or other reasons) and detailed characteristics of deep metastasis that necessi‐ tates careful planning of surgical approach and exact data on the involvement of anatomical structures. Occasionally, differential diagnosis with benign lesions can be complicated. The

Software-based three-dimensional CT volumetrics is used to calculate the volume of the remnant and total liver volumes excluding nonfunctional spaces as tumours, cysts and ablation cavities. The remnant liver volume is expressed as a proportion of the preoperative total liver volume. The minimal volume of remnant liver has not been established by exact experimental

**4. Preoperative radiologic evaluation: the target parameters**

presence and extent of extrahepatic disease must be estimated [18].

benign lesions, e.g., haemangioma [19].

174 Recent Advances in Liver Diseases and Surgery

[1].
