Gastrointestinal and hepatology · Easy
This case is fictional and exists for study. It describes no real patient.
62 years · male
A 62-year-old man presents to his general practitioner complaining of a 10-week history of persistent change in bowel habit toward looser stools, opening his bowels 4 to 5 times daily compared to his usual once daily. He has also noticed dark red blood mixed with the stool intermittently over the last month. He denies significant weight loss, fever, or night sweats. On physical examination, his abdomen is soft and non-tender with no organomegaly or palpable abdominal masses. Digital rectal examination demonstrates normal anal sphincter tone and no palpable rectal masses or gross blood on the glove.
Vital signs
- HR
- 78 bpm
- BP
- 128/82 mmHg
- RR
- 14/min
- Temp
- 36.8 °C
- SpO₂
- 98%
Examination findings
- Abdomen soft, non-tender, no palpable abdominal mass
- Digital rectal examination: normal sphincter tone, no rectal mass felt
Investigations
| Haemoglobin | 10.2 g/dL | reference: 13.5-17.5 |
| Mean Corpuscular Volume (MCV) | 74 fL | reference: 80-100 |
| Serum Ferritin | 12 ug/L | reference: 30-300 |
Question 1 of 3
Which of the following is the single most appropriate management step for this patient?
In accordance with NICE NG12 guidelines, patients aged 50 and over presenting with unexplained rectal bleeding accompanied by a change in bowel habit, or patients aged 60 and over with unexplained iron deficiency anaemia or change in bowel habit, meet the criteria for an urgent referral on a 2-week wait suspected colorectal cancer pathway. Commencing iron alone delays diagnosis. Faecal calprotectin is used to investigate suspected inflammatory bowel disease in younger patients without red flag symptoms. Routine non-urgent referral is inappropriate due to the high index of suspicion for colorectal malignancy.
Teaching point: THREE replacements in plab1--colorectal-cancer-referral-crite--cc709b7266.json. (1) questions[0].teaching_point (line 65) — replace with: "Unexplained rectal bleeding in a patient aged 50 or over meets suspected colorectal cancer referral criteria in its own right; no second symptom is required. Only in adults under 50 must rectal bleeding be accompanied by a further unexplained feature, such as abdominal pain or weight loss, before referral is considered." (2) questions[0].explanation (line 64) — replace the first sentence only, leaving the rest of the paragraph intact: "In accordance with NICE NG12, unexplained rectal bleeding in a patient aged 50 or over is by itself sufficient to trigger the suspected colorectal cancer pathway, and a second symptom is required only in adults under 50. This man meets the threshold several times over: unexplained rectal bleeding at 50 or over, and, at 60 or over, both an unexplained change in bowel habit and iron-deficiency anaemia." (Retain unchanged the existing sentences beginning "Commencing iron alone delays diagnosis." through "...high index of suspicion for colorectal malignancy.") (3) key_learning_points[0] (line 95) — replace with: "NICE NG12 recommends urgent referral on the suspected colorectal cancer pathway for unexplained rectal bleeding in a patient aged 50 or over on that finding alone; pairing rectal bleeding with a second unexplained feature is the criterion for considering referral in adults under 50." Register note: British English throughout, "iron-deficiency anaemia" hyphenated per NICE house style (the file currently writes "iron deficiency anaemia" unhyphenated at line 64 and "iron deficiency anaemia" at line 90 — cosmetic, not part of this finding).
Question 2 of 3
Which of the following is the most appropriate definitive diagnostic investigation for this patient?
Colonoscopy is the gold standard diagnostic investigation for suspected colorectal cancer as it allows direct visualization of mucosal lesions and enables tissue biopsy for histological confirmation. CT abdomen/pelvis is typically reserved for staging or as CT colonography if colonoscopy is contraindicated or incomplete. FIT is used to triage symptomatic patients who do not meet clear high-risk referral criteria or in screening, but not as the definitive diagnostic tool when red flag criteria are already met. Barium enema is largely obsolete in modern standard practice.
Teaching point: Colonoscopy is the gold standard investigation for confirming or ruling out suspected colorectal cancer.
Question 3 of 3
How should the laboratory findings be interpreted in the context of this patient's clinical presentation?
The laboratory results display a low haemoglobin, low MCV, and low ferritin, which is classic for iron deficiency anaemia. In an older male with rectally visible blood and altered bowel habits, iron deficiency anaemia must be assumed to stem from chronic GI blood loss until proven otherwise. Normocytic anaemia of chronic disease typically presents with normal or high ferritin levels. Macrocytic anaemia presents with elevated MCV. Dietary deficiency is a rare primary cause of severe iron deficiency in older men in Western countries without underlying chronic blood loss.
Teaching point: Unexplained microcytic iron deficiency anaemia in men or postmenopausal women must be investigated for gastrointestinal blood loss and underlying malignancy.
Key learning points
- NICE guidelines recommend an urgent 2-week wait referral for colorectal cancer in patients aged >= 50 with unexplained rectal bleeding AND change in bowel habit.
- Colonoscopy is the definitive diagnostic modality for evaluating suspected lower gastrointestinal malignancy as it permits direct biopsy.
- Iron deficiency anaemia in older adults is considered gastrointestinal blood loss secondary to malignancy until investigated and proven otherwise.
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