There are several alternatives available to a flexible sigmoidoscopy. These will vary slightly depending on your situation and you may have already had some of them done.
The tests usually start from the simplest, such as
a rectal exam done with the doctor's finger
testing stool for blood
barium enema x-ray
and proceed to more complicated tests, like
Cat Scan, CT or MRI
If you have questions about your particular situation, you should discuss the different alternatives with your doctor and decide which one, if any, is appropriate for you.