Well the primary test is a colonoscopy and that takes about
4 hours, from arrival until you are fully alert
and ready to resume normal activities. The prep the day before is mostly done in the evening at home. So you should be able to work with your doctor to get that scheduled. If he wants to do a small bowel follow through that can also be done in a half day, with only a fast the evening before. These are not inpatient hospital tests and should be able to be accommdated with most any schedule. Just discuss it with the doc and see what they can work out.