Graduated injection needles and snares for polypectomy are useful for measuring colorectal polyp size

Accurate measurement of polyp size during colonoscopy is important; however, visual estimation of polyp size is inaccurate, and it is cumbersome to use additional accessories to measure polyp size whenever polyps are detected.

To evaluate the accuracy and usefulness of graduated devices that can also be used for polypectomy.

The ends of the outer sheath of the injection needles and snares were marked at intervals of 5mm (total 30mm). Four endoscopists measured 53 polyps of 36 patients in the following manner: visual estimation, estimation with biopsy forceps, and measurement with graduated devices. Actual size of all polyps measured through a calliper was used as reference standard.

The difference between actual size and size measured by visual estimation was statistically significant (1.27mm, P<0.001), whilst the differences between actual size and size measured by biopsy forceps (0.06mm, P=1.00) or graduated devices (0.15mm, P=0.620) were not. The linear correlation between the estimates and the actual sizes showed that the graduated device gave the largest positive linear correlation (0.986, P<0.001) of the three measurement methods tested.

The graduated devices are efficient methods when measuring polyp size and performing polypectomy in a single step.