Abdominal & Pelvic CT sensitivity

  Dear Doctor;
  Male, 40 year old.  Can you satisfy my curiosity?
  How sensitive would an abdominal/pelvic CT with oral contrast be in
  in visualizing a napkin ring growth in the distal sigmoid colon?
  (Axial images, 8mm intervals).
  Realizing CEA is not typically used as a screening blood test
  would it be unreasonable to perform a CEA in the following situation?
  Random red blood on ribbon thin stools. Random morning vomiting now.
  Continuous LLQ & RUQ pressure and pain.
  Elevated venous ammonia,increased from 108 to 122 uMoL/L.
  Increasing ESR from 8 to 15 to 23mm/HR.
  CBC normal, Monocytes High, .8 cumm.
  Random increases in other liver function test. GGT and Bilirubin.
  Alk. Phos. normal.
  Thanks.
  Robert Muller
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Dear Bob Muller,
You have posed very interesting questions regarding the diagnosis of colon cancer.  When CT scans are performed in patients with colon cancer, there are some who will have a thickening of the colon wall and evidence of stranding into the fat.  These findings, however, are not specific to colon cancer.  Conditions such as diverticulosis and Crohn