Abstract 1029: Small Hypoattenuating Lesions in the Liver on Helical CT in Preoperative Patients with Gastric and Colorectal Cancer: Incidence, Significance, and Differentiating Features
AUTHORS:
H. Jang, MD, H.K. Lim, MD, W. Lee, MD, S.H. Kim, MD, J. Yun, D. Choi, MD.
ABSTRACT:
PURPOSE: To determine the incidence and significance of small hypoattenuating lesions in the liver seen at helical CT in preoperative patients with gastric and colorectal cancers and to evaluate the efficacy of CT in differentiating metastases from benign lesions.
MATERIALS AND METHODS: Among 1415 patients with proved gastric and colorectal cancers during a 2-year period, preoperative contrast-enhanced helical CT (7 mm/7 mm, 7-mm reconstruction intervals; 70-sec delay after administration of 120-mL contrast material) was performed in 1133 patients. One radiologist reviewed their images and selected 289 patients (25.5%) with small (< 15 mm) hypoattenuating lesions in the liver. Twenty-one patients without final diagnosis were excluded. Diagnosis was established by follow-up CT examination over 6 months, biopsy, or other confirmatory studies (e.g. US for cysts and MR for hemangiomas). Size, margin (discrete, intermediate, poor), shape (round, other shapes), attenuation (markedly low, intermediate, slightly low), and enhancement features of the lesions were evaluated by the consensus of two radiologists.
RESULTS: Among 885 lesions in 268 patients, 693 lesions (78.3%) in 248 patients (92.5%) were benign and 188 lesions (21.2%) in 30 patients (11.2%) were metastases; 10 patients (3.7%) had both benign and malignant lesions. When excluding cases accompanied by other hepatic metastasis larger than 15 mm, only 14 lesions (1.6%) in six patients (2.2%) were metastases. The size of the benign lesions and metastases was 6.4 ± 3.1 and 9.3 ± 2.7, respectively (P < .001). Benign lesions more frequently had discrete margin (P < .001).
CONCLUSIONS: The incidence (25.5%) of small hypoattenuating lesions in the liver seen at helical CT in preoperative patients with gastric and colorectal cancers was higher than that of other reports with conventional CT; however, the proportion of metastases only presented as small lesions was very low (1.6%). Careful analysis of helical CT findings - discrete margin, markedly low attenuation, lack of rim-enhancement, and no accompanying large metastasis - can be helpful to differentiate benign lesions from metastases.
