Yes, but not always. CT is excellent at showing the organs, lymph nodes and surrounding structures which can be involved with cancer. We can not always see cancer in the organs. Other times CT will show us an abnormality but we don’t know if it’s cancer or benign.
How can we increase the chances of cancer being detected on CT?
CT for cancer is best done with oral and iv contrast given prior to the scan. This allows us to see the most detail and distinguish bowel from abnormalities. Having prior studies also helps because we can see changes over time. An appropriate history also helps the radiologist with the diagnosis and to evaluate for subtle abnormalities.
CT will not show all cancers
Some cancers are diagnosed with blood tests and biopsies. Other cancers are diagnosed with special tests like colonoscopy for colon cancer. Some cancers are subtle and not seen on the CT. There will be abnormalities in the abdomen and organs which will be uncertain as far as cancer.
Fortunately, we have other tests to workup abnormalities. These can include MRI, PET CT and biopsy. Biopsy lets the pathology doctor examine the tissue under the microscope and often arrive at the diagnosis.
There is a range of suspicion on CT for identifying cancer
Sometimes, the abnormality seen on CT is highly suspicious for cancer. They have features which can not represent a benign abnormality. For example, a mass in the pancreas which is irregular, has encased blood vessels, and obstructs the bile and pancreatic ducts will almost always be pancreatic cancer.
Kidney tumors have a characteristic appearance on CT. They will enhance after giving iv contrast. They will become higher in density after giving contrast intravenously because they are vascular. Some benign tumors can do this also but we can’t tell without doing surgery.
Liver tumors can have a characteristic appearance. They will have a dense appearance when scanned early after giving intravenous contrast and then wash out or become darker later on during the scan.
Some abnormalities of the organs, lymph nodes and surrounding tissues will not be characteristic. They may be low to intermediate in suspicion for cancer and not have the classic appearance. Further imaging, follow up or biopsy may be appropriate for workup.
Therefore, CT can identify cancer in the abdomen in many cases. However, some cancers are not seen on CT and diagnosed with other tests. Other cancers may be seen but are not definitely cancer and need further workup. Some cancers may be too subtle to see with the technique used.
Therefore, it is important to remember that a negative CT does not rule out cancer nor does a positive one definitely rule it in. further testing including biopsy will often be needed to confirm the diagnosis.