Nursing care
Colorectal Cancer nursing care: what to assess and what to do first
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Colorectal cancer nursing care centres on recognising a change in bowel habit with rectal bleeding as the trigger for referral, since screening alone starts at 45 for average-risk adults and will not catch symptomatic disease earlier. Priorities are assessing bleeding and bowel pattern, preparing for colonoscopy and biopsy, and monitoring for obstruction, anaemia and perforation.
Recognising it at the bedside
The finding that should move colorectal cancer up your differential is a sustained change in bowel habit accompanied by blood, whether bright red or occult. Constipation alternating with diarrhoea, narrowed stool calibre, or a new urge to defecate that does not resolve with a bowel movement all warrant the same question: has this been assessed with a scope. Patients often describe the change as gradual, which is exactly why it gets dismissed as diet or stress.
Ask about the duration and pattern of the change, not just its presence. A two-week change after a course of antibiotics reads differently to a six-month change with unexplained weight loss and fatigue. Palpate the abdomen for a mass or distension, and ask directly about blood in stool rather than waiting for the patient to volunteer it, since embarrassment keeps many patients quiet until bleeding is heavy or pain has started.
Why the classic presentation misleads
Right-sided colon cancers bleed slowly and rarely cause visible blood in stool, so patients present with fatigue, pallor and a positive faecal occult blood test rather than haematochezia. Left-sided and rectal tumours are more likely to cause the textbook picture of bright red bleeding and altered bowel habit, but by the time obstruction develops the disease is often locally advanced.
This split matters for triage. An older adult with unexplained iron-deficiency anaemia and no gastrointestinal complaints at all still needs colonoscopy referral, because normal-looking bowel habit does not rule out a right-sided lesion. Do not let the absence of visible blood or the absence of bowel change reassure you; screening starts at 45 for average risk precisely because early right-sided disease is otherwise silent.
Priority nursing actions
Establish baseline vital signs and a full blood count on any patient presenting with rectal bleeding or a bowel habit change with blood, since haemoglobin and haematocrit tell you whether bleeding has been acute or chronic. A change in bowel habit with blood is the referral trigger — document it clearly and escalate for colonoscopy rather than treating symptomatically and waiting to see if it settles.
Perform a focused abdominal assessment for distension, tenderness or a palpable mass, and monitor bowel sounds if obstruction is suspected. Keep the patient NPO if surgery or urgent endoscopy is likely. Provide privacy and a non-judgemental tone when discussing bowel and rectal symptoms; patients delay reporting these more than almost any other symptom, and a rushed or visibly uncomfortable interaction reinforces that delay.
Labs and diagnostics to expect
Faecal immunochemical testing or guaiac faecal occult blood testing may be the first clue, but colonoscopy with biopsy is the diagnostic gold standard and cannot be substituted by stool testing alone. Full blood count identifies anaemia; iron studies distinguish iron-deficiency anaemia from other causes and support the case for a gastrointestinal source.
Carcinoembryonic antigen (CEA) is drawn as a baseline tumour marker, useful for monitoring treatment response and recurrence rather than for diagnosis. CT of the chest, abdomen and pelvis stages the disease once biopsy confirms malignancy. Prepare patients for bowel prep before colonoscopy and explain that biopsy results, not the scope itself, confirm the diagnosis, since anxious patients often expect an answer on the day.
Complications and their early signs
Bowel obstruction presents with worsening abdominal distension, absent or high-pitched bowel sounds, vomiting and inability to pass stool or flatus; report this promptly, as it can progress to perforation. Perforation itself is a surgical emergency, signalled by sudden severe abdominal pain, rigidity and fever with signs of peritonitis.
Chronic blood loss produces iron-deficiency anaemia with fatigue, pallor, tachycardia and exertional dyspnoea, sometimes the only presenting sign in right-sided disease. Postoperatively, watch for anastomotic leak (fever, tachycardia, increasing abdominal pain around day five to seven) and for stoma complications if a colostomy or ileostomy has been formed, including ischaemia, retraction or peristomal skin breakdown.
Teaching that changes outcomes
Teach every patient the referral threshold plainly: any change in bowel habit lasting more than a couple of weeks, especially with blood, needs assessment rather than watchful waiting. Reinforce that average-risk screening colonoscopy starts at 45, and that a family history of colorectal cancer or polyps, or a personal history of inflammatory bowel disease, moves that starting age earlier.
For patients newly diagnosed or postoperative, teaching shifts to practical self-management: stoma care and skin protection if applicable, recognising the signs of obstruction or infection at home, and the importance of attending scheduled CEA and imaging follow-up rather than only returning if symptoms recur. Address diet cautiously — there is no single proven preventive diet, so avoid promising outcomes that fibre or supplements alone cannot deliver.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our gastrointestinal practice questions are the closest set to what this page covers.
Common questions
At what age does colorectal cancer screening start?
Screening starts at 45 for average-risk adults. Patients with a family history of colorectal cancer or polyps, or with inflammatory bowel disease, are screened earlier, and the exact starting age varies by that risk history and by guideline, so confirm the individual plan rather than assuming a single fixed age applies.
What is the single symptom that should trigger urgent referral?
A change in bowel habit accompanied by blood, whether visible or occult, is the trigger for referral regardless of the patient's age or screening status. Do not wait for weight loss or pain to appear before escalating.
Why can colorectal cancer present with anaemia alone?
Right-sided colon tumours bleed slowly into the bowel lumen without producing visible blood in stool, so chronic occult blood loss shows up as iron-deficiency anaemia rather than haematochezia. Unexplained anaemia in an older adult warrants colonoscopy even without gastrointestinal symptoms.
What postoperative complication should a nurse watch for around day five to seven?
Anastomotic leak typically presents in this window with fever, tachycardia and increasing abdominal pain. Report these findings promptly, as delayed recognition allows peritonitis to develop.
Is CEA used to diagnose colorectal cancer?
No. CEA is a tumour marker used as a baseline and for monitoring treatment response and recurrence after diagnosis. Diagnosis requires colonoscopy with biopsy.