Contrast can be administered multiple ways, most commonly intravenously (IV) or orally (PO). Less common methods include per rectum, in joints, into the spinal canal.
CT in general is not the best way to evaluate colon or rectal cancer, which is why screening/diagnosis is done with colonoscopy. CT can be useful for other gastrointestinal pathologies, like diverticulosis/itis or obstruction.
The CT protocol that has the best chance to evaluate colon or rectal cancer is one WITH intravenous AND oral contrast. However, cancer can still be occult on CT even with IV and PO contrast.
This is general information and does not constitute medical advice. Please discuss your options with your doctor.
Stage IIA rectosigmoid CC (T3N0M0)
Dx 6/5/17 @age 41, mom to 5 & 2yo girls
Workup: c-scope, EUS, rectal MRI, CT C/A/P
AdenoCA 5.5cm, WHO Grade 2, 0/22 LN, no distant mets
CEA 1.9 (6/5/17), 0.8 (2/28/18)
No lymphovasc/perineural invasion, clear margins
MSI intact, OncotypeDx RS 7
Lap sig colectomy 6/23/17, no ileo/colostomy
Genetics counseling negative for mutations, 4 VUS
Xeloda monotherapy 8/13/17-1/22/18
PET/CT 3/21/18 NED