A colonoscopy is a test that allows doctors to look inside the large intestine for possible tumours and Bush last underwent such clinical examination in 2002. His doctors recommend he receive one every five years to check for colorectal cancer. Doctors removed polyps, which can be a precursor to cancer, from Bush before he became president.

In 2002, Bush has not had any symptoms, White House spokesman Tony Snow said. "Although no polyps were noted in the exam in 2002, age and history would suggest that there's a reasonable chance that polyps will be noted this time," Snow explained. "If so, they'll be removed and evaluated microscopically."

Because the procedure requires that the president goes under anesthesia, Bush will hand over hand over the authority to US Vice President Dick Cheney.

The procedure will be performed by a team of doctors from the National Naval Medical Center at Bethesda, Md. under the supervision of Dr. Richard Tubb, the president's doctor.