Assessing the size of polyp phantoms in tandem colonoscopies

The size of colorectal neoplastic polyps is important for their clinical management.

The size of 12 polyp phantoms was assessed in tandem colonoscopies carried out by 7 endoscopists differing in years of clinical endoscopical experience. The endoscopists measured, with (n=5) or without (n=2) the aid of open forceps, the largest diameter of 12 polyp phantoms. Measurements in two independent trials were compared with the gold standard-size assessed at The Department of Production Engineering, The Royal Institute of Technology.

In tandem trials, 99.4% (167/168) of the measurements underscored the gold standard size. In the 1st trial, the size in all 84 measurements was underestimated by -40% (range -34% to -45%) and in the 2nd trial the size in 83 of the 84 measurements was underestimated by -34% (range -24% to -42%). Neither the age of the participant, nor the years of experience with clinical endoscopy improved the results obtained. The participants significantly underestimated larger devices (>or=20 mm) whereas the smallest "polyps" were also underestimated, but with a lower degree of inaccuracy. The absolute difference between the golden standard size and the mean of all measurements performed on each polyp in 167 out of 168 measurements followed a regular downward trend. The volume of the devices was one of the confounding factors in size assessment. When compared to the gold standard size, the larger the "polyp" size, the higher the degree of underestimation. This may be crucial considering that the risk for colorectal adenomas to shelter an invasive growth is 46%, for adenomas measuring >or=2 cm, a limit accepted as a guideline worldwide for the management of patients with large colorectal polyps.

Considering the clinical implications of the results obtained, the possibility of developing a method that would allow the assessment of the true size of polyps in clinical colonoscopy, is being explored.