Once the diagnosis of colorectal cancer is confirmed, staging of the disease is done before the treatment plan is decided upon. The purpose of staging tests is to assess the local extent of tumour penetration and to detect the presence of spread of the tumour to other organs (i.e. liver and lungs). Staging is important for the doctors to decide on the treatment plan. Staging tests include:

• CT (Computer tomography) scan
  A CT (computerised tomography) scanner is a special kind of X-ray machine. Instead of sending out a single X-ray with
  ordinary X-rays, several beams are sent simultaneously from different angles through the part of interest. The
  computer then processes the results, displaying them as a two-dimensional picture shown on a monitor.

• MRI (Magnetic resonance imaging) scan
  An MRI machine appears similar to the CT scanner, except it uses a magnetic field with radio frequencies introduced 
  into it. MRI is superior to CT scan in examining certain parts of the body.

• PET scan (Positron emission tomography)
  PET scan is a useful tool to evaluate the extent of cancer in a patient. Unlike CT scan and MRI scan where anatomical 
  abnormality is detected, PET scan detects functional abnormalities, hence detecting primary cancer and metastases.
  However, the specificity of PET scan is not perfect. Currently PET scan is only used in some selected patients.

• Endorectal ultrasound
  Endorectal ultrasound is a specialized ultrasound application used in preoperative
  staging of rectal cancer. It can determine the depth of tumour penetration into the rectal wall and also determine the 
  extent of regional lymph node involvement. These information is important for the doctor to decide on the treatment
  plan for rectal cancer.

Updated:: 13/03/2019 []