Loose Stool For A Month- Now GONE!

My dad is 71 years old.  For a month he had loose stools in the evening before going to bed.  He had numerous stool samples, blood tests, and an MRI on his gallbladder area-  all coming back normal.  After a month of loose stool, his stool is now back to normal, and has been for about a week now.  His doctor wants him to go get a CT scan and a colonoscopy, even though he is no longer having symptoms.  Should he still go through with these tests?  Any ideas of what he could have?  I thought it was some sort of lactose or gluten intolerance... but I'm no doctor.  Any help, advice, anything would be great!  TIA!

[mammo]

I wouldn't proceed with the testing given your father only had a problem for a month.  IF it should return then maybe then. Since he had them only at night, I think it was diet related. This is over-kill on the doctorr's part as your father has nothing to warrant further testing.