Diagnosis and imaging of gastrointestinal tract cancers

Recent trends in the diagnosis and imaging of cancers of the gastrointestinal tract include developments in screening for colorectal cancer and innovations in ultrasonography and magnetic resonance imaging of primary and metastatic hepatic tumors. Mathematical models suggest that screening for colorectal cancer will be as cost-effective as several other widely accepted screening programs, including the Papanicolaou smear for cervical cancer and screening mammography. There is considerable discussion regarding the relative roles of procedures such as fecal occult blood testing, sigmoidoscopy, colonoscopy, and radiology in screening strategies. The issue remains unsettled. In ultrasonography, the use of intraoperative ultrasound allows for the detection of more metastatic lesions in the liver than do preoperative computed tomography and ultrasound. Esophageal endoscopic ultrasonography has been used for the preoperative assessment of depth of invasion by esophageal cancer. The technique is limited in cases of stenotic cancer in which the endoscope cannot be passed through the lesion. Similarly, endorectal ultrasound can be used for staging of rectal cancer. Color Doppler ultrasound has been used for the evaluation of blood flow in relationship to hepatic neoplasms. Magnetic resonance imaging has been used not only for detecting liver tumors but also for differentiating between neoplasm and hemangioma.