Reliability of the reported size of removed colorectal polyps

The size of colorectal polyps is important in the clinical management of these lesions.

To audit the accuracy in calculating the size of "polyps" by various specialists.

Eighteen pathologists and four surgeons measured, with a conventional millimetre ruler, the largest diameter of 12 polyp phantoms. The results of two independent measurements (two weeks apart) were compared with the gold standard-size assessed at The Royal Institute of Technology, Sweden.

Thirty-one percent (83/264-trial 1) and 33% (88/264-trial 2) of the measurements underestimated or overestimated the gold standard size by >1 mm. Of the 22 experienced participants, 95% (21/22-trial 1) and 91% (20/22-trial 2) misjudged by >1 mm the size of one or more polyps. Values given by 13 participants (4.9%) in trial 1 and by 15 participants (5.7%) in trial 2, differed by > or = +/-4 mm from the gold standard size. In addition, a big difference between the highest and the lowest values was recorded in some polyps (up to 11.4 mm). Those disparate values were regarded as a human error in reading the scale on the ruler.

Using a conventional ruler (the tool of pathologists worldwide) unacceptably high intra-observer and inter-observer variations in assessing the size of polyp-phantoms was found. The volume and the shape of devices, as well as human error in reading the scale of the ruler were confounding factors in size assessment. In praxis, the size is crucial in the management of colorectal polyps. Considering the clinical implications of the results obtained, the possibility of developing a method that will allow assessment of the true size of removed clinical polyps is being explored.