How to extract the liver from initial segmentation?

I want to extract the whole liver from CT image.

Initial probability map is given below in an image.

I want to extract the red part. Discard other parts. I am using morphological operations but the result is as follows.

because the probability map in the upper part of a liver having a tumor. This part is the black probability which is nearly equal to the background. Please guide me the best solution. Thanks.