Problem in Gall bladder. Exact problem?

My father has pain due to problem in Gall bladder, We have performed surgery 15 year back for Gall stone and his bladder was removed. Now Sonography suggest, there is no gall bladder with mention of Cystic area in Gall bladder fossa with echogenic sludge measuring -3.5 x 2.4 x 2.3cm. However CT scan suggest there is Gall bladder present which mentions Enhancing thickening of wall of Gall bladder and cystic duct with adjacent fat standing. Eccentric enhancing wall thickening of the fundus involving adjacent liver parenchyma. Posibility of acute choleccystitis, however asymmetric thickening of the fundus underlying occult neoplasm. Mild dilatation of cystic duct and CBD with tiny non obstructing calculas in diatal CBD MRCP suggested. Doctor says may be partial bladder was removed 15 years back . I am not getting correct solution. whether my Father has to under go further surgery, since he has pain occasionally or can be cured through medicine. what is the exact problem?