BACKGROUND: Some patients with colorectal carcinoma have liver metastases(LMs) which cannot be detected by conventional imaging. This study aimed to assess whether hepatic perfusion changes induced by micrometastases can be detected by perfusion computed tomography(CT).METHODS: LMs were produced in rats by injecting carcinoma cells into the portal vein. Perfusion CT was performed at microscopic(day 10), interval(day 17), and macroscopic stage(day 34). Perfusion parameters were computed using a dualinput one-compartmental model.RESULTS: Micro and macro LMs presented a mean diameter of 0.5 and 2.6 mm, respectively. Compared to controls, LMs at interval(1.1 mm) and macroscopic stage induced significant perfusion changes: a decrease of 42%(P=0.004) and 41%(P=0.029) in hepatic transit time and an increase of 292%(P=0.073) and 240%(P=0.001) in portal delay, respectively.CONCLUSIONS: LMs with a mean diameter between 1.1 and2.6 mm induced significant hepatic perfusion changes, detected by CT. Such detection may help to select patients and propose chemotherapy at the time of primary tumor resection. BACKGROUND: Some patients with colorectal carcinoma with liver metastases (LMs) which can not be detected by conventional imaging. This study aimed to assess whether hepatic perfusion changes induced by micrometastases can be detected by perfusion computed tomography (CT). METHODS: LMs were produced in rats were injected with carcinoma cells into the portal vein. Perfusion CT was performed at microscopic (day 10), interval (day 17), and macroscopic stage (day 34). Perfusion parameters were computed using a dualinput one-compartmental model. Compared to controls, LMs at interval (1.1 mm) and macroscopic stage induced significant perfusion changes: a decrease of 42% (P = 0.004) and 41% (P = 0.029) in hepatic transit time and an increase of 292% (P = 0.073) and 240% (P = 0.001) in portal delay, respectively. CONCLUSIONS: LMs with a mean diameter between 1.1 and 2.6 mm significant significant hepatic perfusion changes, detected by CT. Such detection may help to select patients and propose chemotherapy at the time of primary tumor resection.