eP501 - Re-defining the Rectal Anatomy into Clinically Relevant Halves

Sunday, June 2, 2024

3:48 PM – 3:53 PM ET, USA

Location: Baltimore Convention Center, Room 318-320

ePoster Presenter(s)

Ashley Althoff, DO

Colorectal Surgery Fellow
AdventHealth
orlando, FL, United States

All of the relevant financial relationships listed below have been mitigated.
This individual has no financial relationships with ineligible companies.

Author(s)

LB

Lindsey Bridges, DO

Colorectal Surgery Fellow
Advent Health
AdventHealth
Orlando, FL, United States

All of the relevant financial relationships listed below have been mitigated.
This individual has no financial relationships with ineligible companies.
Andrew-Paul Deeb, MD, MSc

Colon & Rectal Surgery Fellow
AdventHealth Colorectal Surgery
Orlando, FL, United States

All of the relevant financial relationships listed below have been mitigated.
This individual has no financial relationships with ineligible companies.
KS

Katherine Specht, DO, MS

Colorectal Surgery Fellow
AdventHealth
Orlando, FL, United States

All of the relevant financial relationships listed below have been mitigated.
This individual has no financial relationships with ineligible companies.
AD

Andrew Dakkak, PGY IV M.D., M.B.A

Diagnostic Radiology Resident, PGY IV
AdventHealth Orlando
Orlando, Florida, United States

Disclosure information not submitted.
NJ

Nicholas Jaeger, DO

Diagnostic Radiology Resident
AdventHealth
Orlando, Florida, United States

Disclosure information not submitted.
MD

Man B. Dai, M.D.

Diagnostic Radiology Resident
AdventHealth Orlando
Lawrenceville, Georgia, United States

Disclosure information not submitted.
NF

Nicholas Feranec, Md

Radiologist, Body Section Chief
Advent Health Central Florida
Winter Park, Florida, United States

Disclosure information not submitted.

Senior Author(s)

John RT Monson, MD

Professor of Surgery
Northwell Health
Northwell Health
Ridgefield, CT, United States

Disclosure information not submitted.

Purpose/Background: Historically, the rectum has been divided into anatomic upper, middle and lower thirds based on measurements from the anus. The upper and lower extent have a lack of consensus with the some defining this as the sacral promontory and anal verge respectively and others as S3 and the dentate line. The development of rectal magnetic resonance imaging (MRI) has allowed the peritoneal reflection to delineate the transition from the intraperitoneal to extra-peritoneal rectum. This is therefore often used to define the transition from the upper and middle rectum. Defining anatomic landmarks that are identifiable on imaging is imperative as the treatment for rectal cancer is increasingly dependent on the location of the cancer in relation to the peritoneal location. We sought to define the rectal anatomy based on clinical and therapeutic relevance.Methods/Interventions: Using our prospectively maintained database of the National Accreditation Program for Rectal Cancer, we reviewed pre-treatment rectal cancer protocol MRIs performed within our institution of patients with locally advanced rectal cancer. We sought to evaluate the tumor location in relationship to anatomical landmarks. The following landmarks were accessed for identification and distance from tumor: peritoneal refection (PR), sacral promontory, anal verge, and anal sphincter. All MRIs were reviewed by specialist radiologists. Mostly above or below PR was defined as >50%.Results/Outcomes: 116 MRIs were reviewed. The PR was identified in 93.1% of images. 13.9% of rectal cancers were identified as above the PR, 42.6% below, and 43.5% at the PR (31.9% mostly above PR and 19.1% mostly below). The sacral promontory was only identified in 65.5% of patients and was more likely to be identified for tumors at (70%) or above (80%) the PR. The distance from the tumor and the sacral promontory was 57.1mm, anal sphincter complex 44.2mm, and anal verge 75.5mm. 19.0% of rectal cancers had contact with the anal sphincter. This comprised of 47.8% of tumors below the PR.Conclusion/

Discussion: The majority of rectal cancers are located at or below the level of the PR and can therefore be practically divided into halves rather than the traditional three thirds. Tumor location defined by distance from the sacral promontory or anus seems of little clinical relevance, especially in the era of total neo-adjuvant therapy and potential organ preservation.