Table 1.

Main similarities and differences between the most recent guidelines published by the European Society of Gastrointestinal and Abdominal Radiology (ESGAR) and the North American Society of Abdominal Radiology (SAR).

Similarities
• MRI should be used for rectal cancer primary staging and restaging.
• Endorectal ultrasound is recommended to differentiate between T1 and T2 tumors.
• Minimal field strength requirement for the MRI system is 1.5 T.
• 3 orthogonal planes T2W (sagittal, plus axial and coronal angulated to the tumor axis).
• Coronal T2W parallel to anal canal in distal tumors.
• Optimal slice thickness for T2W is 3 mm (ESGAR) and up to 3–4 mm (SAR)
• DWI is recommended for restaging.
• T1 and contrast images are not recommended.
• MRF involved when distance between the tumor and MRF is < 1 mm
• CR can be diagnosed when two-layered rectal wall is normalized on restaging.
• Using only size threshold for LN staging is not universally accepted
Differences
SAR	ESGAR
• Measurement (mm) of the extent of tumor invasion beyond the bowel wall should be reported. • No consensus on the use of size criteria in primary staging of lymph nodes. • After CRT, nodal downsizing is considered a sign of sterilization.	• Only the discrimination between T3ab (<5 mm) and T3cd (> 5mm) is required regarding the extramural extension depth. • Nodal size criteria, depending on the morphological features. • After CRT, nodes with a short axis < 5 mm are considered sterilized.