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'''== MRI T staging'''==
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== Choice of modality ==
'''MRI (first choice)'''
* Mandatory for both primary staging and restaging of rectal cancer.
'''Endorectal ultrasound (EUS)'''
* Staging for early tumours considered for local excision
* Superior diagnostic performance for differentiating T1 from T2 tumors.
== Patient preparation ==
'''Spasmolytics (optional)'''
* Can be benefical for upper rectal tumors and when imaging is performed at 3.0T (bowel movement artifacts are most prevalent)
'''Endorectal filling (optional) (~60 ml of gel)'''
* When used, some experts suggest using a volume of only ~60 ml of gel, since higher volumes will compress perirectal tissues significantly
* Useful to reduce susceptibility artefacts related to luminal gas during diffusion-weighted MRI.
* Its use is not reccomended routinely: rectal wall distension may interfere with interpretation of the distance between the tumour and the mesorectal fascia, and high T2 signal of the gel may cause T2 shine through effects on DWI.
== T staging ==
**T4b: Directly invades or is adherent to other organs/structures
* MRI doesn't differentiate T1 from T2
*'''T1-T2: limited to intestinal wall'''
** '''T3c or T3d: >5 mm extramural growth'''
* '''T4'''
=== Information relevant to surgical approach ===
For low tumours with sphincter invasion, describe:
Depth of invasion
* invades only the internal sphincter muscle
* also involves the intersphincteric plane
* also involves the external sphincter
Height of invasion
* involves only the proximal 1/3 of the complex/anal canal
* also involves the middle 1/3 of the complex/anal canal
* also involves the lower 1/3 of the complex/anal canal
* involves pelvic floor (levator)
== N staging ==
