Chapter 08 — Rectal Bleeding and Colorectal Cancer Triage

Purpose: visible rectal bleeding is a symptom, not a diagnosis — decide in minutes whether it is dangerous now, then decide whether the colon must be examined before anyone treats haemorrhoids.

🎨 INFOGRAPHIC / VISUAL BLUEPRINT — CHAPTER 08

• Chapter colour palette: Steel Blue (#0369A1) header bar, Ice (#F0F9FF) panels, Deep Navy (#0C4A6E) text.
• Hero graphic: Two-stage triage board. Stage 1, “Is it dangerous now?”: a monitor showing heart rate ÷ systolic BP = shock index, with a red zone above 1. Stage 2, “Is there a cancer behind it?”: an alarm-feature checklist beside a FIT tube with a gauge marked at 10 µg Hb/g, leading to a colonoscope.
• Icon set: Blood drop with clock, heart-rate monitor, FIT sample tube, colonoscope, family tree, weighing scale, iron tablet with question mark.
• Bedside aphorism banner: ““It looks like piles” is an observation, not a diagnosis — the colon decides.”

1. Differential Diagnosis by Age and Context

Table 8.1 — Common causes and must-not-miss diagnoses

2. What the Blood Tells You — and What It Cannot

Table 8.2 — Characterising the bleeding

The colour and timing of blood are useful clues, but no pattern reliably excludes cancer [C]. Decisions rest on alarm features, examination, and — where available — FIT.

3. Alarm Features — Examine the Colon Before Blaming Haemorrhoids

Table 8.3 — Alarm features

⚠️ EARLY-ONSET COLORECTAL CANCER

Young age does not exclude colorectal cancer. Persistent bleeding, a change in bowel habit, or anaemia in a 30- or 40-year-old still needs investigation.

Algorithm 8.1 — Visible rectal bleeding in the ER or clinic

[VISIBLE RECTAL BLEEDING]
|
STEP 1 - IS IT DANGEROUS NOW?
|  HR, BP, shock index (HR / systolic BP), postural drop,
|  syncope, ongoing heavy bleeding, Hb, antithrombotics
|
+-- Shock index > 1 after resuscitation, or ongoing heavy
|   bleeding -> RED: resuscitate; senior + surgery/GI;
|   group and crossmatch; CT angiography to localise
|   (BSG 2019); melaena or raised urea -> think UPPER GI
|
+-- Stable -> STEP 2
|
STEP 2 - WHERE IS IT COMING FROM?
|  Inspect, DRE, anoscopy: fissure? haemorrhoids? mass?
|
+-- Rectal or anal MASS or ulcer
|     -> YELLOW: urgent suspected-cancer referral now
|        (no FIT needed; Chapter 07 for anal lesions)
|
STEP 3 - MUST THE COLON BE EXAMINED FIRST?
|  Any alarm feature? (age/screening, IDA, weight loss,
|  bowel-habit change, family history, IBD, positive FIT,
|  persistent bleeding)
|
+-- YES -> YELLOW: colonoscopy (or CT colonography if
|     colonoscopy unsuitable) BEFORE haemorrhoid procedures
|
+-- NO, and a clear anal source is seen
      -> GREEN: treat fissure/haemorrhoids (Chapters 03-04)
      -> REVIEW at 4-6 weeks: still bleeding?
         -> treat as an alarm feature: colon evaluation

4. When Haemorrhoid Treatment May Proceed — and When the Colon Comes First

Table 8.4 — Treat now or investigate first

5. Investigations and Referral Pathways

Table 8.5 — Choosing the test

6. Acute Severe Bleeding — Key ER Numbers (BSG 2019)

• Shock index (heart rate ÷ systolic BP) > 1 after initial resuscitation = unstable: CT angiography to localise, then interventional radiology or endoscopy; consider an upper GI source if no lower source is found [S/C].

• Stable patients: the Oakland score helps decide disposal — a score of 8 or less identifies patients who can usually be discharged for outpatient investigation [C]. The score was derived in the UK; apply with clinical judgement.

• Transfusion: restrictive approach — threshold about 70 g/L with a target of 70–90 g/L; about 80 g/L with a target of 100 g/L in patients with cardiovascular disease [C].

• Antithrombotics [C][L]: do not routinely stop aspirin taken for secondary prevention; withhold warfarin or DOACs in major bleeding and reverse for life-threatening haemorrhage per local protocol; involve cardiology or haematology for recent stents or high thrombotic risk.

7. Documentation Template for Rectal Bleeding

Table 8.6 — Rectal bleeding documentation template

💬 PATIENT EXPLANATION — WHY “IT LOOKS LIKE PILES” IS NOT A DIAGNOSIS

“I can see some swollen veins (piles) that could explain your bleeding. But piles are very common, and they can sit next to something more important higher up in the bowel that I cannot see from here. Because of [your age / your blood test / the change in your bowel habit / your family history], the safe step is to look at the whole bowel first. Most people turn out to have a simple cause — but if there is something else, finding it early makes it much easier to treat.” Return straight away if: you pass a lot of blood or clots, feel faint or dizzy, or have severe tummy pain.

A printable patient handout on rectal bleeding appears in Appendix F.

8. Dangerous Mimics

Table 8.7 — Rectal bleeding mimics

9. Role-Targeted Action Boxes

🚑 ER DOCTOR ACTION BOX

• Calculate the shock index for every rectal bleed. Above 1 after resuscitation: senior review, crossmatch, CT angiography, and the surgical or GI team.
• Melaena or a raised urea in an unstable patient suggests an upper GI source — arrange upper endoscopy.
• A stable patient with a low Oakland score can usually be discharged with an outpatient investigation plan — not with a cream and no follow-up.

🩺 FAMILY MEDICINE / GP CLINIC BOX

• Examine every patient with rectal bleeding (inspection, DRE, anoscopy where available) and check Hb and ferritin.
• Screen for alarm features and use FIT where your pathway provides it; refer directly for a rectal or anal mass or anal ulcer.
• Book a 4–6-week review for patients treated for an anal source; persistent bleeding becomes an alarm feature.

🏥 ER & WARD NURSE CARE AND SBAR BOX

• SBAR escalation triggers [C][L]: shock index > 1; systolic BP < 90 mmHg; heart rate > 120/min; repeated passage of fresh blood or clots; new confusion or syncope; or a haemoglobin fall of 20 g/L or more.
• Record a stool and bleeding chart, and keep large-bore IV access patent in admitted patients.

💊 CROSS-SPECIALTY PRESCRIBING TRAP

• Iron without investigation: treating IDA with oral iron and no endoscopic work-up can hide a colorectal cancer. Investigate and replace iron together.
• Oral iron darkens stool and can be mistaken for melaena (it is not sticky or tarry); it does not cause a positive FIT.

⛔ NEVER DO THIS

• Never attribute iron-deficiency anaemia to haemorrhoids before the GI tract has been investigated.
• Never refer for banding or haemorrhoidectomy without colon evaluation when alarm features are present.
• Never discharge a patient whose shock index stays above 1.
• Never let a negative FIT override strong clinical suspicion of cancer.
• Never assume a young patient cannot have colorectal cancer.

📝 COMMON DOCUMENTATION ERROR

• “PR bleed — likely piles” without observations, examination, haemoglobin, alarm-feature screen, or follow-up plan.
• A FIT result filed without action, or a positive FIT without a referral date.

📨 REFERRAL URGENCY BOX

The Patient in Front of You — Chapter 08 Mini-Case

🧑‍⚕️ THE PATIENT IN FRONT OF YOU

A 47-year-old man is referred by his GP for “banding of bleeding piles”. He has had intermittent bright-red bleeding for 3 months and feels more tired than usual. Haemoglobin is 112 g/L, MCV 74 fL, and ferritin 9 µg/L. His father had colon cancer at 58. Anoscopy shows grade II internal haemorrhoids.

Step 1 Count the alarm features: iron-deficiency anaemia, a first-degree relative with colorectal cancer, and age at or near screening age.

Step 2 Do not band yet. Haemorrhoids on anoscopy do not explain iron-deficiency anaemia.

Step 3 Investigate: urgent bidirectional endoscopy (colonoscopy and upper endoscopy) per BSG 2021, with iron replacement started alongside.

Step 4 Outcome and lesson: colonoscopy shows a 3 cm sigmoid adenocarcinoma; the haemorrhoids were bystanders. Treat the haemorrhoids only after the colon has been cleared or the cancer managed.

Board-Style Question — Chapter 08

A 74-year-old woman taking apixaban for atrial fibrillation presents with large-volume maroon rectal bleeding. After 1 litre of crystalloid her heart rate is 118/min and systolic BP 92 mmHg (shock index 1.28). Upper GI symptoms are absent and urea is normal. What is the most appropriate next step?

• A. Discharge with an outpatient colonoscopy in 2 weeks
• B. CT angiography after resuscitation, with senior, surgical/GI, and interventional radiology involvement
• C. Rubber band ligation of visible internal haemorrhoids
• D. Faecal immunochemical test and review in clinic

Answer and explanation

• ❌ A An unstable patient with ongoing bleeding cannot be discharged.
• ✅ B Correct. A shock index above 1 after resuscitation defines an unstable lower GI bleed; BSG 2019 recommends CT angiography to localise bleeding before radiological or endoscopic therapy. Withhold apixaban and use reversal per local protocol if bleeding is life-threatening; consider an upper GI source if CT angiography is negative.
• ❌ C Banding does not address a large-volume maroon bleed, which is unlikely to be haemorrhoidal.
• ❌ D FIT is a triage tool for stable symptomatic patients in primary care, not for acute haemorrhage.

Ten-Item Rapid Revision Checklist — Chapter 08

• 01 I calculate the shock index for every rectal bleed.
• 02 I consider an upper GI source in unstable patients, especially with melaena or raised urea.
• 03 I examine (inspection, DRE, anoscopy) and check Hb and ferritin.
• 04 I screen every patient for the alarm features in Table 8.3.
• 05 I investigate iron-deficiency anaemia with bidirectional endoscopy.
• 06 I use FIT where available and know the 10 µg Hb/g threshold.
• 07 I refer a rectal or anal mass directly without waiting for FIT.
• 08 I delay haemorrhoid procedures until the colon is cleared when alarm features are present.
• 09 I book a 4–6-week review for bleeding attributed to an anal source.
• 10 I use the documentation template and give written safety-net advice.

Five Most Dangerous Mistakes — Chapter 08

1. ⚠️ Banding haemorrhoids in a patient with iron-deficiency anaemia and missing a colorectal cancer.
2. ⚠️ Discharging an unstable bleeding patient because “it is only piles”.
3. ⚠️ Missing an upper GI bleed presenting as maroon rectal bleeding.
4. ⚠️ Accepting a negative FIT despite a mass, weight loss, or persistent symptoms.
5. ⚠️ Dismissing persistent bleeding in a young adult.

Suggested Figure and Table Captions for the Medical Illustrator — Chapter 08

• Figure 8.1. Two-stage triage board: “dangerous now?” (shock index) and “cancer behind it?” (alarm features and FIT).
• Figure 8.2. Where bleeding comes from: anal outlet, rectum, colon, and upper GI tract, with typical blood patterns.
• Figure 8.3. Colonoscopy view: haemorrhoids at the outlet and a sigmoid cancer proximally — “piles can coexist with cancer”.
• Table 8.1. Common causes and must-not-miss diagnoses by context.
• Table 8.2. Characterising the bleeding.
• Table 8.3. Alarm features.
• Table 8.4. Treat now or investigate first.
• Table 8.5. Choosing the test.
• Table 8.6. Rectal bleeding documentation template.
• Table 8.7. Rectal bleeding mimics.
• Algorithm 8.1. Visible rectal bleeding in the ER or clinic.