1.

Colorectal cancer diagnosis

Aim	Class I recommendation	Class II recommendation	Class III recommendation
a, In principle, full colonoscopy is forbidden in patients who are known to have clinical intestinal obstruction. b, Patients with intestinal obstruction should not undergo barium enemas. c, When liver metastases are suspected by ultrasound (US)/computed tomography (CT) examinations, particularly potentially resectable liver metastases, abdominal magnetic resonance imaging (MRI) scans should be conducted. MRI includes T2 weighted imaging, diffusion-weighted imaging (DWI), multiphase contrast-enhanced MRI, and other imaging markers that can effectively determine the quantity, size, and distribution of liver metastases (1). Patients with certain indications can undergo enhanced MRI with a hepatocyte specific contrast-agent, as this method will aid in detecting more liver lesions less than 1 cm (2). d, Pelvic MRI is the most accurate test to define locoregional clinical staging of rectal cancer. ERUS may define the locoregional staging for earliest tumors (3). e, CT reconstruction images are used to determine the location, invasion depth, relative relationship with surrounding structures and organs, regional lymph node metastases, and peripheral vascular invasion of colon cancer. f, Positron emission tomography (PET)/CT should not be used routinely for initial clinical staging of colorectal cancer (4-6).
Diagnosis	Full colonoscopy + biopsya Rectal cancer: digital rectal examination	Barium enemab Virtual colonoscopy Rectal cancer: contrast-enhanced CT/MRI pelvic scan; sigmoidoscopy + biopsy; transrectal biopsy Colon cancer: contrast-enhanced abdominal/pelvic CT; exploratory surgery	—
Staging-primary tumors (subjects with a confirmed diagnosis by colonoscopy)	Rectal cancer: high resolution pelvic MRI scanc; Endoscopic rectal ultrasound (ERUS)d Colon cancer: contrast-enhanced chest/abdominal/pelvic CTe	Rectal cancer: contrast-enhanced pelvic CT Colon cancer: noncontrast chest CT scan and contrast-enhanced abdominal/pelvic MRI	—
Staging-distal metastases (subjects with a confirmed diagnosis by colonoscopy)	Contrast-enhanced chest/abdominal/ pelvic CTe	Serum carcinoembroynic antigen/CA199 Noncontrast chest CT scan and contrast-enhanced pelvic MRI	Chest X-rays Pelvic ultrasound
Staging (ultrasound or CT for patients with suspected liver metastases)	Contrast-enhanced abdominal MRI	Hepatocyte specific contrast-enhanced MRI	Liver ultrasound
Staging (suspected metastases according to aforementioned imaging tests but cannot be determined)	PET/CTf	—	—
Examination before major treatment decisions	—	PET/CTf Hepatocyte specific contrast-enhanced MRI	Liver ultrasound