C.T. Results

I have a 4 cm polyp discovered by colonoscopy.  It is at the top of my rectum and has, so far, been designated benign (this is after two biopsies).  Also, I had a rectal ultrasound of the polyp and surrounding area, and everything appeared to be okay.  I am scheduled for surgery to remove the polyp in mid-March, and, as part of the work up, I had a C.T. scan.  The scan revealed a mildly dilated biliary tree, a common cyst (.5 mm) on the liver and a common cyst (.5 mm) on the kidney.  I am scheduled for an MRCP on the 14th.  Is it possible that everything can be okay, or does there have to be something wrong with the biliary tree?  In other words, can the slight dilation be caused by something other than cancer?  (I have no gallstone symptoms.)