BACKGROUNDAlthough the computer tomography (CT) or magnetic resonance imaging (MRI) findings of alveolar echinococcosis (AE) have been well documented, the consecutive imaging changes of this disease in each PNM stage (parasite lesion, neighboring organ invasion, metastases) were not described accurately. The aim of this study was to analyze the correlation between imaging type and PNM stage and diameter of AE lesions, and to explore the development features of this disease.

METHODSA total of 87 patients with AE were examined using CT and MRI before medical management. Imaging features including the maximum diameter, calcification pattern, and imaging type of lesion were retrospectively assessed. The correlation of imaging type with PNM stage, diameter and calcification pattern was analyzed.

RESULTSLesions (n=111) in 87 patients were divided into three types based on imaging characteristics; solid type (33.3%, 37/111, a solid lesion without liquid necrosis or only small patches of necrosis), mixed type (41.4%, 46/111, solid component surrounding large and/or irregular liquid necrosis area), and pseudo-cystic type (25.2%, 28/111, large cyst without visible solid component). Lesion calcification in the alveolar echinococcosis was categorized into three patterns; mild calcification (45.1%, 50/111, i.e. inconspicuous calcification or punctuate scattered calcification), moderate calcification (46.8%, 52/111, coastline calcification located at the periphery of the lesion, with or without the central dot-calcification) and abundant calcification (8.1%, 9/111, large calcified deposits). Significant differences were found between pseudo-cystic type and other two types in PNM stage, maximum diameter and calcification (P <0.05), but there was no significant difference between solid type and mixed type in those mentioned aspects (P >0.05). No correlation was observed between calcification patterns and maximum diameter (P >0.05).

CONCLUSIONSSolid and mixed type lesions showed some similarities during the course of the disease and accounted for the major form of advanced AE. Pseudo-cystic type represented neither earlier nor advanced stage of AE, but a special presentation during AE development.