Diagnosis

The pre-operative evaluation of patients with hepatic metastases from rectal cancer must include an accurate staging of the primitive rectal cancer, of the liver metastases (number, site and size of hepatic metastases) and of extra-hepatic disease. The imaging techniques utilised for pre-operative evaluation are: ultrasound, CT, MRI and PET.

Ultrasound examination plays an important role in detecting liver metastases and is able to identify very small lesions within the liver. Sensitivity is good and varies from 86 to 90%, with a specificity higher than 90%. Obesity, presence of intestinal meteorism and liver steatosis can limit the efficacy of the technique. Moreover, subglissonian and posterior metastases, especially smaller than 1 cm, are difficult to detect. Colorectal metastases with ultrasound may be either hyperechoic or hypoechoic, even if in 80% of the cases they are hyperechoic surrounded by a hypoechoic halo. Differentiation from primary tumours or benign lesions is most difficult when lesions are smaller than 1.5 cm. In these cases, for a better characterisation of the lesion and its vascularisation, the use of contrast-enhanced ultrasound may be helpful.

Computed tomography is the most accurate and widely available technique for detecting and characterising liver metastases. Moreover, CT has a primary role in staging rectal cancer. Sensitivity in identifica tion of liver metastases reaches 70-85%, with a specificity of 90%, especially for lesions bigger than 1.5-2 cm. CT sensitivity is lower for small liver subglisson-ian metastases even though recent multi-slice CT allows identification of hepatic lesions of 0.5 cm in size.

Hepatic metastases from rectal cancer are hypo-dense without contrast medium; after the contrast medium they are hypodense during the arterial phase; and they are remarkably hypodense in the portal phase in comparison with the surrounding healthy parenchyma (Fig. 1).

Magnetic resonance imaging (MRI) has gained approval in recent years and shows good sensitivity and specificity in the diagnosis of hepatic lesions. Sensitivity varies from 85 to 90%; specificity is higher than CT, up to 95%. MRI in liver metastases is useful in the characterisation of the lesion (differential diagnosis between primary and secondary liver tumours) and in definition of the precise relationship between lesions and vascular structures. The use of paramagnetic contrast agent (gadolinium-DTPA) or iron oxide-based superparamagnetic contrast media (SPIO) allows an increase in the sensitivity and specificity of the methodology, even though it is still in an assessment phase.

Positron emission tomography (PET) in liver metastases has high sensitivity and high specificity, 92-100% and 85-100% respectively. Sensitivity in small lesions (<1 cm) is limited and it does not show relevant improvements of its diagnostic ability in comparison with CT and MRI.

The diagnostic role of monoclonal antibodies conjugated with radioactive compounds is still not conclusive. An advantage of their application has still not been demonstrated, and moreover, nowadays high costs are not justified.

Fig. 1. CT and surgical field of a liver metastases of rectal carcinoma. The lesions are located on the left lobe

Table 2. Predictor of recurrence after hepatic resection for metastatic colorectal cancer

Study Patient Primary Metastases age stage

Synchronous Size Number Bilobar Satellite

Study Patient Primary Metastases age stage

Synchronous Size Number Bilobar Satellite

Chemo Surgical CEA margin

Foster [6]

-

N

N

Y

Y

-

-

-

-

-

Adson et al. [7]

-

N

N

N

N

N

-

-

-

-

Fortner et al. [8]

N

Y

-

N

N

-

-

N

-

N

Butler et al. [9]

N

Y

N

N

N

-

-

N

N

-

Nordlinger et al. [10]

-

-

-

N

N

-

-

-

-

-

Cobourn et al. [11]

-

N

N

-

Y

-

N

-

-

-

Hughes et al. [4]

-

Y

Y

Y

Y

Y

-

Y

Y

Y

Schlag et al. [12]

-

-

Y

-

-

-

-

-

-

-

Doci et al. [13]

N

Y

N

N

N

N

-

-

-

N

Younes et al. [14]

-

N

N

Y

Y

-

-

-

-

Y

Scheele et al. [15]

N

Y

Y

N

N

N

Y

-

Y

-

Rosen et al. [16]

-

N

N

N

N

-

Y

-

N

-

Cady et al. [17]

N

N

N

N

Y

-

-

-

Y

Y

Fong et al. [18]

N

Y

Y

Y

Y

Y

-

Y

Y

Y

Gayowsky et al. [19]

Y

Y

N

N

Y

Y

-

-

Y

-

Nordlinger et al. [20]

Y

Y

Y

Y

Y

N

-

-

Y

Y

Scheele et al. [21]

N

Y

Y

Y

N

N

Y

-

Y

Y

Fong et al. [22]

N

Y

Y

Y

Y

Y

-

-

Y

Y

Minagawa et al. [23]

N

Y

N

N

Y

N

-

-

N

Y

Scheele et al. [24]

Y

Y

Y

Y

Y

N

N

Y

N

Y

Chemo Surgical CEA margin

Intraoperative diagnosis is based on intraoperative ultrasound and on diagnostic laparoscopy. The sensitivity of intraoperative ultrasound is very high, reaching 98-100%. It allows identification of small metastases of 0.5 cm in size and defines the relationship between lesion, vessels and biliary structures. For these reasons it must be considered as a routine investigation to be performed in all patients with hepatic metastases, which is able to modify planned surgical intervention in more than 30% of patients.

Laparoscopy, which is not routinely used in the pre-operative evaluation of the advanced disease, allows a reliable study of the peritoneal and pelvic diffusion of the primitive rectal cancer. The combined use of laparoscopic ultrasound (LIOUS) also allows identification of the presence of small metastases, modifying the initial surgical project in 20-30% of cases.

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