Role of Gadoxetic Acid-Enhanced Magnetic Resonance Imaging in the Preoperative Evaluation of Small Hepatic Lesions in Patients with Colorectal Cancer

The initial abdominal computed tomography (CT) scans of patients with colorectal cancer (CRC) sometimes reveal equivocal hepatic lesions. In this study, we evaluated the outcomes of equivocal hepatic lesions found by abdominal CT and the diagnostic accuracy of subsequent liver magnetic resonance imaging (MRI). We evaluated data of patients who underwent CRC resection between January 1, 2009 and December 31, 2009. Equivocal hepatic lesions of < 1 cm in size on preoperative staging CT scans were included in this study. Gadoxetic acid-enhanced liver MRI was subsequently performed in all patients. Hepatic lesions that grew during the follow-up period (a parts per thousand yen3 years) were considered potential metastases. Overall, 121 equivocal hepatic lesions were detected on preoperative staging CT in 65 out of 494 patients (13.2 %) who underwent colorectal surgery. Based on subsequent MRI, 11 lesions were classified as definitive metastatic lesions and 100 were classified as definitive benign lesions, including simple cysts or hemangiomas. Findings in the other 10 lesions were still inconclusive even after examining CT and MRI. Of the 11 lesions that were classified as metastatic by MRI and were resected, 10 were pathologically confirmed as metastases and one lesion was a pathologically benign nodule. All 100 benign lesions were stable on follow-up imaging and were classified as benign. Of the 10 equivocal lesions, 6 increased in size during the follow up, suggesting they were early metastases, while 4 were stable. The sensitivity and specificity for detecting liver metastases by gadoxetic acid-enhanced MRI of small equivocal hepatic lesions found by CT were 100 % (16/16) and 95.2 % (100/105), respectively, if MRI was equivocal or indicated definite metastasis. The negative predictive value was 100 % (100/100). Gadoxetic acid-enhanced MRI is a useful diagnostic tool for assessing equivocal hepatic lesions on preoperative CT of CRC patients that allows increased diagnostic accuracy and detection of additional colorectal liver metastasis lesions.