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1721. Magnetic Resonance Imaging for Determination of Rectal Anatomic Dimensions and the Anterior Peritoneal Resection
Authors * Denotes Presenting Author
  1. Yusra Waheed *; Aga Khan Hospital
  2. Muhammad Awais; Aga Khan Hospital
Objective:
Colorectal cancer accounts for the third most common cause of death by cancer. Previous studies have used invasive methods such as rigid endoscopy or intraoperative proctoscopy to measure the distance from the anal verge to the anterior peritoneal reflection (APR). Comparatively MRI is not only non-invasive but its measurements are easily reproducible and verifiable. Moreover, no data exists regarding the rectal anatomic features and landmarks in our population to guide the surgeons. The aim of this study is to estimate the rectal canal length and the level of anterior peritoneal reflection (APR) using MRI.

Materials and Methods:
Data of 100 individuals who underwent pre-treatment MRI pelvis for the evaluation of rectal carcinoma from Jan 2016 to Dec 2018 was retrospectively analyzed. After excluding patients with prior history of surgery or chemo/radiotherapy related to rectosigmoid region, biopsy proven cancer patients were 30. Rest of the 70 patients who were negative for rectal malignancy was included as healthy group. The relevant demographic, radiological and histopathological findings were recorded on a pre-structured proforma. Rectal canal length, distance of the peritoneal reflection from the anal verge and length of the anal canal was measured on sagittal T2 MR Sequence.

Results:
The mean rectal canal length, distance of peritoneal reflection from Anorectal Junction (ARJ) and distance of anorectal junction from anal verge values were 14.3 cm, 11.2 cm and 3.4 cm respectively in disease population whereas 10 cm, 8.2 cm and 4.7 cm in healthy population. These results show that anatomical dimensions appear relatively less in local population in comparison to western population. This is likely explained due to the differences in body habitus and built.A statistical significant change in anatomical dimension in presence of rectal malignancy is also noted ( p = 0.0003, 0.001 and 0.004) for rectal length, APR and anal canal respectively.

Conclusion:
This study, which is first in our population, shows that rectal canal length and the level of peritoneal reflection are different in our population as compared to the western population. The rectal anatomical dimension and level of peritoneal reflection vary among different population of the world due to difference in body habitus and build.Therefore, treatment decisions made on the basis of the western data might not be applicable to our population and indigenous local guidelines should be developed.