Haematochezia and lower GI bleeding

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Lower gastrointestinal bleeding usually arises distal to the ileocaecal valve but clinical presentation overlaps upper and small-bowel sources. Haematochezia is fresh or maroon blood passed per rectum; severe upper bleeding can transit rapidly, while slow right-colon bleeding can produce dark stool. Ask about quantity and recurrence, abdominal or anal pain, diarrhoea, change in bowel habit, weight, previous diverticular disease, IBD, radiotherapy, endoscopy and vascular disease. Medicine history must specify warfarin, direct oral anticoagulant, antiplatelets, NSAIDs and exact last dose. Examine perfusion, abdomen, groins and anus, and perform a consented rectal examination when it will assess blood, mass or anorectal source.

Risk stratification controls the route. The BSG defines instability using shock index above one as a practical marker and recommends CT angiography when an unstable patient is suspected of active bleeding. Positive arterial extravasation leads urgently to catheter angiography and embolisation where available; surgery is reserved for uncontrolled haemorrhage after localisation and multidisciplinary discussion. If CTA is negative and haemodynamics remain concerning, an upper source needs investigation. In stable disease, the Oakland score helps separate a minor self-terminating bleed from a major bleed, but comorbidity, social reliability, anticoagulation and clinician concern modify disposition.

Causes have characteristic but overlapping patterns. Diverticular haemorrhage is often painless; angioectasia is recurrent and may be occult; cancer causes change, iron deficiency or intermittent blood; IBD and infection cause diarrhoea and urgency; ischaemic colitis causes acute pain followed by blood, often after hypotension or with vascular risk. Colonoscopy diagnoses mucosa and provides some haemostasis but requires preparation and may miss intermittent small-bowel bleeding. Follow-up must address histology, cancer exclusion, iron deficiency and medicine restart even when bleeding stops spontaneously. A visible haemorrhoid is not a universal causal diagnosis.

Key points

Classify unstable versus stable first; a shock index above one is a useful BSG warning, but beta-blockade, pacing and older age can conceal tachycardia.
Describe bright red, dark red or maroon blood, clots, mixing with stool, dripping, pain and melaena, but colour alone does not reliably locate a brisk bleed.
In unstable ongoing bleeding, CT angiography is the fastest widely available test to localise active haemorrhage and direct interventional radiology or surgery.
If CT angiography does not identify a lower source in an unstable patient, assess for upper gastrointestinal bleeding promptly because rapid upper bleeding may pass fresh.
Stable patients are stratified as major or minor with a validated tool such as the Oakland score plus clinical judgement; low score is not a discharge command.
A major stable bleed is admitted for colonoscopy on the next available list after preparation, while a minor self-terminating bleed may undergo urgent outpatient investigation when safe.
Diverticular bleeding is often painless and brisk, ischaemic colitis usually combines pain and blood, and anorectal disease commonly leaves blood on paper or surface; none is proven without adequate assessment.
Review anticoagulants, antiplatelets and NSAIDs immediately. Reversal, interruption and restart depend on bleeding severity and thrombotic indication and require named specialist ownership.
Rectal examination and proctoscopy can identify distal disease, but finding haemorrhoids does not explain anaemia, weight loss or a separate proximal cancer risk.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Diverticular and vascular bleeding

Diverticular arterial rupture and colonic angioectasia commonly cause painless overt bleeding, particularly in older adults taking antithrombotic medicines.

Anorectal sources

Haemorrhoids and fissures produce bright-red blood, but visible anorectal disease should not automatically explain anaemia or persistent change.

Inflammatory, ischaemic and neoplastic

Colitis, colorectal cancer, post-polypectomy injury and other lesions bleed through mucosal inflammation, ulceration or tumour friability.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Colonic vessel or mucosal injury
Arterial rupture, inflammatory ulceration or tumour erosion releases blood into the colon or rectum before distal passage.
2
Visible distal transit
Rapid passage preserves a bright or maroon appearance, while site and transit determine whether blood coats, mixes with or precedes stool.
3
Volume-dependent systemic effects
Ongoing loss reduces circulating volume and oxygen delivery, with initial haemoglobin sometimes remaining deceptively normal before redistribution.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Unstable active haemorrhageRed flag

Ongoing large-volume blood with shock index above one, syncope, hypotension, cool peripheries, oliguria or raised lactate indicates major active bleeding and supports immediate resuscitation and CT angiography.

Diverticular bleeding

Sudden painless substantial haematochezia in an older adult with diverticulosis supports a diverticular arterial source. Bleeding often stops spontaneously but can recur, and other causes still need exclusion.

Ischaemic colitisRed flag

Abrupt cramping abdominal pain followed by bloody diarrhoea, often left sided and after hypotension or with vascular disease, raises colonic ischaemia. Peritonism, acidosis or right-sided disease increases concern for transmural injury.

Inflammatory or infectious colitis

Blood mixed with diarrhoea, urgency, fever and abdominal pain supports colitis. Travel, antibiotic, immunosuppression and chronicity distinguish infection, C difficile and IBD and determine sampling before immunosuppression.

Colorectal malignancy

Persistent or intermittent blood with altered bowel habit, weight loss, iron-deficiency anaemia or a mass requires the current FIT-supported suspected-cancer pathway even if bleeding seems minor.

Anorectal source

Bright blood on paper or coating stool with anal pain, prolapse or itching suggests fissure or haemorrhoid. Anaemia, weight loss, blood mixed through stool or a bowel-pattern change prevents premature closure.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Serial physiology and shock indexFirst step
Why
Identify unstable bleeding and measure response to resuscitation before definitive localisation.
Interpretation and limitations
Shock index above one supports instability, but medication and age may blunt it. Trend perfusion, urine output, lactate and bleeding rather than using one calculated value alone.
02
Full blood count, coagulation and crossmatch
Why
Assess blood loss and platelet status, identify medicine-related coagulopathy and prepare blood components.
Interpretation and limitations
Early haemoglobin can be normal; serial change is affected by fluid. Record anticoagulant type and last dose because routine INR does not quantify direct oral anticoagulant activity.
03
CT angiography
Why
Rapidly localise active bleeding in an unstable or ongoing major bleed and guide embolisation or operative planning.
Interpretation and limitations
Contrast extravasation directs urgent interventional radiology. A negative scan during intermittent bleeding does not prove absence; persistent instability prompts upper-source assessment and multidisciplinary re-evaluation.
04
Colonoscopy
Why
Identify diverticular, vascular, inflammatory, neoplastic and anorectal pathology and provide selected endoscopic haemostasis.
Interpretation and limitations
Major stable bleeding is investigated on the next available list after appropriate preparation. Poor preparation reduces detection and therapy, and a negative examination may redirect to upper or small-bowel investigation.
05
Upper gastrointestinal endoscopy
Why
Identify a brisk upper source when haematochezia accompanies shock or when lower-source CTA is negative.
Interpretation and limitations
Melaena, raised urea, liver disease or haematemesis strengthens the upper question, but absence does not exclude it in rapid transit.
06
Quantitative FIT
Why
Support urgent outpatient colorectal cancer triage in eligible stable symptomatic patients after immediate bleeding care is addressed.
Interpretation and limitations
FIT is not the resuscitation test for major overt haemorrhage. Apply the commissioned pathway and refer persistent high-risk symptoms or a mass despite a low result.
07
Stool and inflammatory testing
Why
Investigate infectious or inflammatory colitis when diarrhoea, fever, travel, antibiotics or chronic symptoms accompany bleeding.
Interpretation and limitations
Send exposure-specific microbiology and use calprotectin in an appropriate non-acute-severe setting. Do not start corticosteroids until important infection is considered.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Brisk upper-GI haemorrhage

Instability, melaena, haematemesis, cirrhosis or no lower source after angiography should prompt urgent upper-GI assessment and endoscopy.

Minor anorectal bleeding

Blood on paper or dripping after stool with clear fissure or haemorrhoids supports a distal source, but alarm features require further investigation.

Inflammatory or ischaemic colitis

Bloody diarrhoea with chronic inflammatory features suggests IBD, whereas abrupt cramping after hypotension or vascular stress favours ischaemic colitis.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Unstable bleedLocalise during resuscitationFirst stepHaematochezia continues with shock or a shock index above one.

1Begin ABCDE, obtain large-bore access, crossmatch, monitor urine output and activate local major-haemorrhage support according to physiology.
2Call gastroenterology, colorectal surgery and interventional radiology early and arrange CT angiography without allowing transport to interrupt resuscitation.
3DefinitiveIf CTA shows active bleeding, proceed urgently to angiography and embolisation or the locally agreed definitive intervention.
4If CTA is negative but instability persists, investigate an upper source promptly and continue multidisciplinary reassessment rather than labelling the bleed resolved.

02Stable bleedSeparate major from minorThe patient is haemodynamically stable after initial assessment.

1Calculate an Oakland score accurately and combine it with comorbidity, ongoing blood, haemoglobin, anticoagulation, examination and social reliability.
2EscalationAdmit major bleeds for bowel preparation and colonoscopy on the next available list, with earlier escalation if physiology changes.
3Consider discharge only for a self-terminating minor bleed in a suitable low-risk patient, arranging urgent outpatient investigation and explicit return advice.
4Do not attribute bleeding to haemorrhoids without addressing anaemia, mass, bowel change and cancer risk.

03AntithromboticsBalance bleeding and thrombosisThe patient takes anticoagulant or antiplatelet therapy.

1Record drug, indication, last dose, kidney function and thrombotic risk and stop or continue treatment according to bleeding severity and specialist guidance.
2Use the current agent-specific reversal pathway for life-threatening bleeding with haematology and transfusion input rather than improvising from INR alone.
3After haemostasis, agree and document restart timing with the responsible cardiology, stroke, haematology or anticoagulation team and communicate it at discharge.

04After bleedingFind cause and prevent recurrenceHaemodynamics are stable and immediate haemorrhage has stopped.

1Complete appropriate colon, upper or small-bowel investigation based on the bleeding pattern and previous tests, obtaining and tracking histology.
2Treat iron deficiency, IBD, infection, cancer, diverticular or anorectal disease according to diagnosis rather than offering generic reassurance.
3Review NSAIDs and antithrombotics, explain recurrence signs and nominate who will act on outstanding results and arrange surveillance.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

Rapidly reduces ongoing anticoagulant effect while definitive haemostasis and resuscitation are pursued.

Agent-specific anticoagulant reversal

For life-threatening or uncontrolled bleeding, use the current local and BNF reversal regimen matched to warfarin, dabigatran, factor Xa inhibitor or heparin exposure.

Reversal increases thrombosis risk and is not identical for each drug. Confirm last dose and renal function, involve haematology, and create a documented restart decision after bleeding control.

Restores circulating volume and oxygen-carrying capacity while the bleeding site is localised and controlled.

Intravenous crystalloid and blood components

Give warmed crystalloid in limited reassessed boluses and blood components through the local major-haemorrhage or restrictive transfusion strategy according to active physiology.

The first haemoglobin may be misleading. Avoid both under-resuscitation and unnecessary over-transfusion, monitor calcium and temperature during major transfusion, and individualise coronary and heart-failure risk.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Haemorrhagic shock

Large-volume bleeding causes syncope, hypotension and organ hypoperfusion, requiring localisation by CT angiography when ongoing and unstable.

Anaemia and cardiac strain

Chronic or recurrent loss causes iron deficiency, fatigue and myocardial supply-demand imbalance, especially in older people with cardiovascular disease.

Rebleeding or missed pathology

Assuming diverticula or haemorrhoids are causal can delay cancer or inflammatory diagnosis, while untreated vascular lesions often bleed again.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Trend pulse, blood pressure, shock index, perfusion, mental state, urine output and lactate during active or recently controlled bleeding.
Document stool colour and estimated frequency, but base escalation on physiology and haemoglobin trajectory rather than subjective volume alone.
Repeat haemoglobin, platelets, renal function and coagulation after resuscitation and intervention, interpreting dilution and ongoing loss.
After embolisation or endoscopic therapy, watch for recurrent bleeding and new abdominal pain that could indicate bowel ischaemia or procedural complication.
Track colonoscopy, histology, FIT and iron results to a named clinician, ensuring spontaneous cessation does not cancel cancer exclusion.
Audit antithrombotic interruption, reversal and restart communication because undocumented prolonged omission creates preventable stroke or thrombosis.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Fresh does not mean low

A high-rate upper gastrointestinal bleed can cross the bowel before blood is digested, producing maroon or fresh stool. Shock with haematochezia should always keep an upper source alive.

CTA needs active flow

Angiographic techniques detect bleeding occurring during acquisition. Intermittent haemorrhage can yield a negative study, so physiological recurrence should trigger renewed localisation rather than false certainty.

Oakland supports selection

A low score identifies patients more likely to be safe for outpatient care, but comorbidity, continued bleeding, anticoagulation and reliable access to urgent investigation remain decisive.

Haemorrhoids can coexist

Distal bleeding disease is common and visible, which makes it an attractive stopping point. It can coexist with proximal cancer, IBD or angioectasia and does not explain unexplained anaemia automatically.

Ischaemia follows hypotension

Colonic watershed areas are vulnerable after a low-flow episode. Pain followed by blood after hypotension may represent ischaemic colitis even without a large arterial occlusion.

11Common pitfallsFrequent interpretation and management errors.

01
Assuming fresh rectal blood proves a lower source in a shocked patient without considering brisk upper bleeding.
02
Sending an unstable active bleed for routine colonoscopy preparation instead of urgent CT angiography.
03
Using a low Oakland score as an automatic discharge order despite ongoing bleeding or unsafe follow-up.
04
Attributing anaemia and bowel-pattern change to haemorrhoids because they are visible on examination.
05
Reversing or withholding antithrombotic therapy without recording the indication, thrombosis risk and restart owner.
06
Proceeding to surgery for unlocalised bleeding without endoscopic and radiological multidisciplinary planning when feasible.