Location of Lesions 40cm from the Anal Verge

Introduction to Measuring Distance from the Anal Verge

The American Gastroenterological Association recommends measuring the distance from the anal verge to determine the exact location of lesions during colonoscopy, with the rectum spanning from 0-15cm 2
The rectum is divided into three parts: low rectum (0-5cm) 3, mid rectum (5-10cm) 2, and high rectum (10-15cm) 2
The sigmoid colon is located 15-40cm from the anal verge 1, 4
The descending colon is located 40-60cm from the anal verge 1

Lesions at 40cm are typically located at the junction between the sigmoid colon and descending colon, which is part of the left colon 1, 4
The sigmoid colon is the most common site for colorectal cancer (52.6% of malignant polyps), followed by the rectum (35.3%) 4
This location has the highest risk of obstruction due to the narrowness of the colon with formed stool 4

Accurate recording of the location is crucial, using measurements from the anal verge and fixed anatomical landmarks (such as the splenic flexure) 3, 5, 6, 7
The American Society for Gastrointestinal Endoscopy recommends tattooing the location of lesions if future intervention is needed, with ink placed 2-3cm away from the lesion 3, 5, 6, 7
A complete colonoscopy should be performed to rule out synchronous lesions, as 35% of tumors are located farther than the sigmoid colon and 2.5% have synchronous lesions 4
Detailed documentation of the size, shape, and exact location of lesions relative to anatomical landmarks is essential 5, 8, 9