LAUSR

PURPOSE The purpose of this study was to evaluate imaging and clinical features of colorectal liver metastases complicated with macroscopic intrabiliary growth, and correlate the unusual pattern of spread with treatment and follow-up. METHODS A retrospective analysis of the clinical, imaging and follow-up files of all patients with surgically resected colorectal liver metastases from January 2016 to October 2020 was reviewed to identify those with macroscopic intrabiliary growth. Two radiologists evaluated the radiological features of colorectal liver metastasis with macroscopic intrabiliary growth. The histopathological findings and follow-up results were also investigated. RESULTS A total of 555 patients were included. Colorectal liver metastasis with macroscopic intrabiliary growth was present in 5 patients (0.9 %). Four patients experienced tumor recurrence or progression after surgical treatment (80 %), and recurrent tumors retained propensity for intraductal growth. CT (n = 6) and MR (n = 6) examinations were performed before 8 operations with the pathological examination confirmed macroscopic intrabiliary colorectal metastases. According to the location, intrabiliary colorectal metastases were classified into two categories: peripheral (n = 3) and central involvement (n = 5). The lengths of tumoral extension into the downstream bile duct were more than those of extension into the upstream bile duct (P = 0.029). On CT images, all cases showed dilated bile ducts filled with soft tissue attenuation presenting moderate (n = 4) or obvious (n = 2) enhancement. On MR images, all intra-hepatic and intrabiliary components of the metastases showed restricted diffusion on diffusion-weighted imaging, and peritumoral wedge-shaped T1-weighted hyperintensity appeared in the cases with obstruction of intrahepatic bile ducts. CONCLUSIONS The propensity for colorectal liver metastasis with intrabiliary growth to grow longitudinally and extend beyond the intrahepatic tumor edge elevates the risk of high recurrence after operation. Intrabiliary growth of liver metastasis exhibits characteristic MR and CT imaging features, which help to make an accurate diagnosis and improve treatment plans.