1. A computer-implemented method for automatically extracting image date for a colon from computed tomographic image data, the method comprising: automatically identifying a lumenic structure in the image data, such that the lumenic structure includes an automatically established landmark portion of the colon; automatically testing at least one lumenic structure that does not include an automatically established landmark portion of the colon for appropriateness to be appended to the identified lumenic structure; and if the tested lumenic structure is appropriate, appending the tested lumenic structure to the identified structure.