What should you know about colonoscopy for prostate cancer?

Prostate cancer assessment instead relies on prostate-specific tests, which may include a prostate examination, a prostate-specific antigen blood test, imaging and a prostate biopsy.

During colonoscopy, a flexible camera passes through the rectum to inspect the lining of the large bowel. The prostate sits close to the rectum, but it is outside the bowel and cannot be fully assessed through this procedure.

Your care team may suggest colonoscopy because of rectal bleeding, a persistent change in bowel habits or a separate need for colorectal screening. It may also help distinguish an existing bowel problem from treatment-related symptoms or document bowel health before pelvic radiotherapy. The reason should be stated clearly because the procedure answers a bowel question, not the prostate cancer diagnosis itself.

Confirm who requested the colonoscopy and what question it is meant to answer. Tell the endoscopy team about your prostate cancer treatment, previous pelvic radiotherapy or surgery, medicines that affect bleeding, allergies, kidney or heart conditions and any problems with sedation. Do not stop prescribed medicine unless the treating team gives specific instructions.

Follow the bowel-preparation and fasting directions exactly, and arrange transport if sedation is planned. Ask when results will be available and whether they could change the timing of radiotherapy, brachytherapy or prostate surgery. If bowel symptoms began during cancer treatment, record when they started and whether they include pain, bleeding, diarrhoea or constipation.

Contact the endoscopy service promptly after colonoscopy if you develop worsening abdominal pain, fever, repeated vomiting, increasing abdominal swelling, persistent rectal bleeding or black stools. Seek emergency care for heavy bleeding, fainting, severe breathing difficulty or intense abdominal pain. Mild bloating or a small amount of blood can occur after some procedures, but symptoms that worsen or do not settle need assessment.

Separately, inability to pass urine, new leg weakness, loss of bladder or bowel control, or severe back pain requires urgent medical assessment. These concerns should not wait for a scheduled colonoscopy appointment.

Ask: What specific bowel concern is this colonoscopy checking? Is it routine screening or related to my symptoms or treatment plan? Could a biopsy or removal of a bowel polyp affect the timing of prostate cancer treatment? Which medicines should I take on the preparation day? Who will explain the findings, and will both my endoscopy and oncology teams receive the report?