Liver metastases of colorectal cancer: US, CT or MR?

Abstract

In contrast to other extrahepatic malignancies many colorectal cancers can be cured even when there is metastatic spread to the liver. The diagnosis of liver metastases relies totally on imaging to decide which patients may be surgical candidates. The diagnostic value of ultrasound with contrast agents, multidetector CT and MR imaging with non-specific gadolinium chelates and liver-specific contrast agent is discussed. Nowadays MDCT is the mainstay of staging and follow-up of these patients, because it provides good coverage of the liver and the complete abdomen and the chest in one session. MR imaging has been shown to be superior to helical CT in the preoperative assessment of colorectal liver metastases. Large studies are needed to define the role of MDCT vs. MRI staging in patients referred for resection of liver metastases.

Figure 1

Value of unenhanced CT in detection calcified metastases. (A) The unenhanced scan clearly depicts a small calcified metastasis (arrow), which turned out to be vital tumour at surgery. (B) The lesion is hardly seen in the portal-venous phase.

Figure 2

Need for bi-phasic contrast-enhanced scan for detection of mixed vascularity metastatic adenocarcinoma: the arterial-phase scan demonstrates hypovascular and hypervascular metastases (arrows). Incidental note is made of a large metastasis in the spleen.

Figure 3

Value of T2-weighted images and non-specific gadolinium chelates in lesion characterization in a patient with a history of haemangioma in segment 6. (A) The T2-weighted TSE image reveals a moderately hyperintense lesion, suggestive of a metastasis (arrow). There is a second small lesion adjacent to the metastasis, which is very hyperintense on T2-weighted images (arrowhead). (B) On the SPIO-enhanced image, there is better delineation of both lesions. (C), (D) The dynamic gadolinium-enhanced images in the arterial and the delayed phase show peripheral nodular enhancement with pooling in the smaller lesion, indicative of haemangioma (arrow). Patient had developed a colon cancer metastases close to this previously known haemangioma.

Figure 4

Small metastasis and cyst: differentiation with T2-weighted TSE and non-specific gadolinium chelates. (A) The T2-weighted TSE image shows a small cyst, which is very bright (arrowhead). There is a second lesion, which is moderately hyperintense (arrow). (B) The gadolinium-enhanced T1-weighted GRE image shows lack of enhancement of the cyst (arrowhead). The other lesion displays a ring enhancement, which is suggestive of metastasis (arrow).

Figure 5

Comparison of mangafodipir (Teslascan^®)-enhanced MRI and CT. (A) Unenhanced T1-weighted MRI shows some lesions in the liver (arrows). (B) There is much better delineation of the metastases on the mangafodipir-enhanced images. (C) On the contrast-enhanced MDCT, only one metastasis in the left lobe is seen. The other lesions were also not seen on adjacent slices.

Figure 6

Comparison of SHU 555A (Resovist^®)-enhanced MRI and MDCT. (A) On the contrast-enhanced MDCT, a metastasis is only faintly seen (arrow). (B) The SHU 555A-enhanced T2-weighted image depicts a 1.5 cm metastasis in segment 7.