INTRODUCTION: It is generally accepted that clinicians performing colonosco
py should reach the cecum in at least 90 percent of examinations. However,
little attention has been paid to whether the endoscopist correctly estimat
es the amount of colon actually seen. METHODS. During colonoscopy, endoscop
ists were asked to state how far they had reached. This was compared with t
he amount of colon actually seen, as assessed by a novel electromagnetic im
aging device that recorded a three-dimensional position of the score within
a magnetic field pervading the patient's abdomen. If electromagnetic imagi
ng showed that the cecum had not been reached, the endoscopist was asked to
use the electromagnetic imaging system to determine whether it helped adva
nce the colonoscope further. RESULTS: In 119 patients undergoing colonoscop
y, clinical assessment of position reached was correct in only 92 (77.3 per
cent). When the endoscopists stated that cecal landmarks had been seen (n =
85), the scope was distal to the cecum in seven cases (8.2 percent). When
cecal landmarks had not been seen (n = 34), the endoscopist's assessment of
the position of the scope was accurate in only 14 (41.2 percent). The use
of electromagnetic imaging in this latter group assisted passage to the cec
um in 26 cases (76.5 percent). CONCLUSION: Despite assumed visualization of
the cecum, inadequate colonoscopy highlights the potential for missing sig
nificant pathology in the right colon.