Variation in landmarks for the rectum: an MRI study

Abstract

Current definitions of the rectum that rely on arbitrary measurements or bony landmarks will not locate the correct point of transition between the rectum and sigmoid in the majority of patients. The sigmoid take-off offers an alternative, anatomically bespoke, landmark.

The sigmoid take-off: An anatomical imaging definition of the rectum validated on specimen analysis

“…The Sigmoid Take-Off: An Anatomical Imaging Definition of the Rectum Validated on Specimen Analysis Authors Nigel D'Souza MRCS, MEd 1, 2, 3 , Amy Lord MBChB, FRCS 1,2,3 , Annabel Shaw MBBS, FRCS 1, 2, 3 , Anisha Patel MBChB, FRCR 2 , Svetlana Balyasnikova PhD, FRCR 2 , Vera Tudyka MD, FRCS 4 , Muti Abulafi MS, FRCS 1 , Brendan Moran MS, FRCS 5 , Shahnawaz Rasheed PhD, FRCS 2,3 , Paris Tekkis MD, FRCS 2,3 , Monica Terlizzo MD, FRCPath 2 , Nick West PhD, FRCPath 6 , Philip Quirke PHD, FRCPath 6 , Gina Brown MD, FRCR 2,3 1. Croydon University Hospital…”

“…endoscopic visualisation for metric measurements, barium enemas for bony landmarks). Utilisation of these arbitrary landmarks that ignore individual patient anatomy has been shown to incorrectly localise tumours [3][4][5][6] . This may also explain the rise of the term rectosigmoid; to classify tumours that on imaging do not correspond to their localisation by landmarks.…”

MRI of rectal cancer—relevant anatomy and staging key points

“…The definition of the upper limit of the rectum is an intraoperative definition, corresponding to the lower limit of the large bowel that can be mobilised away from the spinal column. On MR imaging, it may correspond to the point of inflection between the more vertical rectum and the more horizontal rectosigmoid or “sigmoid take-off” [ 7 – 9 ] (Fig. 2 a).…”

Detailed and applied anatomy for improved rectal cancer treatment

“…From the radiological aspect, the transition from the mesosigmoid to mesorectum is indicated by the “sigmoid take off”, and can be identified on cross-sectional sagittal imaging, where the sigmoid colon lies horizontally and the rectum follows the hollow of the sacrum. On this cross-sectional imaging, the superior rectal vessels enter the proximal mesorectum and bifurcate into 2 vessels, adjacent to the inferior portion of the pouch of Douglas approximately at the level of S3 [16]. At this point, the proximal part of the rectum is covered by the mesorectum only laterally and posteriorly, while the middle is encased circumferentially, approximately up to the anterior peritoneal reflection.…”

“…Most surgeons (35%) place the proximal rectal border at the level of the anterior peritoneal reflection, though other anatomical or metric landmarks are also used [1]. In contrast, the various CRC specialties place the proximal border at the “sigmoid take off” on cross-sectional MRI imaging, over all other metrics and anatomical landmarks [15,16] (Fig. 1A).…”