Ogilvie's syndrome (acute colonic pseudo-obstruction) is characterized by massive colonic dilation without mechanical obstruction. The key feature is that there is NO mechanical blockage - it's a functional motility disorder. It commonly occurs after surgery, trauma, or with narcotic use. The involvement can be of the entire colon or segments. The statement that it is caused by mechanical obstruction is therefore FALSE, making option A the correct answer to this 'NOT true' question.