Colonic diverticular bleeding

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

Colonic diverticular haemorrhage occurs when the penetrating artery associated with a diverticulum erodes and bleeds into the lumen. Presentation is usually sudden painless haematochezia or maroon stool, sometimes with clots and enough volume to cause syncope. Pain, fever or tenderness should widen the diagnosis to ischaemic colitis, diverticulitis or another inflammatory process. A known diverticular segment raises probability but does not prove the source because diverticula are common and bleeding may have stopped before investigation. A definitive diagnosis is strongest when active bleeding, a non-bleeding visible vessel or an adherent clot is seen within a diverticulum, or angiography localises extravasation at that site.

Assessment follows the acute lower-GI bleeding pathway. Record onset, episodes, stool colour, pain, haematemesis, previous endoscopy, liver disease, vascular history and every anticoagulant, antiplatelet and NSAID dose. Examine circulation, abdomen and anorectum where appropriate. Shock index, serial observations and response to initial resuscitation classify instability more reliably than apparent volume in a photograph. A major bleed can originate above the ligament of Treitz and move rapidly through the bowel; haemodynamic instability with negative lower localisation should prompt upper-GI evaluation. Minor self-terminated bleeding may be risk-stratified for outpatient investigation only when physiology, support and follow-up are secure.

Definitive management depends on whether bleeding is active and whether it can be localised. CT angiography is fast, needs no bowel preparation and directs catheter angiography with embolisation when extravasation is seen. If unstable bleeding continues despite a negative scan, reconsider timing, upper sources and repeat or alternative investigation through the specialist team. Stable major bleeding is investigated with adequately prepared colonoscopy, which can identify and treat a stigmata-bearing diverticulum and diagnose cancer or angiodysplasia. Surgery is a last-resort haemostatic intervention after endoscopic and radiological options or when another operative pathology exists; blind segmental resection without localisation risks failure. After haemostasis, review NSAIDs and antithrombotic indication, correct iron deficiency and communicate the restart plan explicitly.

Key points

Diverticular bleeding is often abrupt, painless and substantial because a vasa recta adjacent to a diverticulum ruptures; many episodes stop spontaneously but recurrence is important.
Do not call bleeding diverticular simply because diverticula were seen previously. Cancer, angiodysplasia, ischaemic colitis, inflammatory disease, haemorrhoids and an upper-GI source need proportionate exclusion.
Judge physiology before estimating colour or volume: calculate shock index, repeat observations, assess perfusion and establish venous access while history is taken.
Haemoglobin can initially appear normal in acute blood loss, so serial values and clinical trajectory are more useful than a single reassuring result.
For haemodynamic instability or suspected active major bleeding, BSG guidance prioritises CT angiography because it rapidly localises arterial extravasation and directs embolisation.
A stable major lower-GI bleed generally requires admission and inpatient colonoscopy on the next available list after preparation; urgent unprepared colonoscopy is rarely effective.
Transfuse red cells using the current restrictive NICE and local major-haemorrhage strategy, individualised for active exsanguination and cardiovascular ischaemia.
Anticoagulant and antiplatelet interruption, reversal and restart must balance active haemostasis against the indication and thrombosis risk with the relevant specialist owner.

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

Diverticular vessel exposure

A vasa recta draped over a colonic diverticulum becomes separated from the lumen by thin mucosa and is vulnerable to focal arterial injury.

Age-related diverticulosis

Bleeding occurs in a minority of people with diverticula, which become more prevalent with age and altered colonic wall structure.

Medicine-associated risk

NSAIDs, antiplatelets and anticoagulants can increase bleeding likelihood or severity, but treatment changes require balancing thrombotic risk.

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

1
Vessel wall injury
Chronic mechanical stress and local mucosal injury weaken the eccentric artery where it crosses the diverticular dome.
2
Arterial luminal bleeding
Rupture releases blood directly into the colon, often causing abrupt painless haematochezia or maroon stool without diverticulitis.
3
Spontaneous haemostasis or recurrence
Many episodes stop as the vessel contracts or thromboses, but the same or another diverticulum can bleed again unpredictably.

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

Typical diverticular haemorrhageRed flag

Abrupt painless passage of red or maroon blood, often with clots, in an older adult with diverticulosis is characteristic, but source attribution remains provisional until localisation or exclusion is adequate.

Haemodynamic major bleedRed flag

Syncope, tachycardia, hypotension, cool peripheries, oliguria, altered mentation or a shock index above the local instability threshold identifies high risk regardless of the initial haemoglobin.

Ischaemic or inflammatory bleedRed flag

Pain before blood, focal tenderness, fever or diarrhoea is atypical for uncomplicated diverticular haemorrhage and raises ischaemic colitis, infection, IBD or diverticulitis.

Upper gastrointestinal sourceRed flag

Melaena, haematemesis, raised urea relative to creatinine, liver disease, ulcer risk or haemodynamic instability with brisk haematochezia warrants parallel consideration of an upper source.

Colorectal neoplasia

Persistent altered bowel habit, iron deficiency, weight loss, a mass or recurrent low-volume bleeding requires cancer-pathway assessment even if an acute episode stopped spontaneously.

Benign anorectal bleeding

Small-volume bright blood on paper with local symptoms may be anorectal, but haemorrhoids should not be used to explain anaemia, clots, dark blood or physiological change without further assessment.

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 observations and shock indexFirst step
Why
Classify haemodynamic instability and response to resuscitation before selecting the diagnostic route.
Interpretation and limitations
Persistent tachycardia or hypotension, worsening perfusion or rising shock index supports major haemorrhage activation and urgent CT angiography; transient improvement does not establish haemostasis.
02
Full blood count, coagulation and group-and-save
Why
Measure anaemia and platelets, identify coagulopathy and prepare matched blood when bleeding is significant.
Interpretation and limitations
Early haemoglobin may not reflect total loss. Serial decline, ongoing bleeding and physiology guide transfusion; INR does not quantify direct oral anticoagulant effect reliably.
03
CT angiography
Why
Rapidly localise active luminal arterial bleeding in an unstable or ongoing major haemorrhage and direct embolisation.
Interpretation and limitations
Contrast extravasation identifies a target for prompt catheter angiography. A negative scan may mean intermittent cessation and does not exclude a major upper or lower source.
04
Prepared colonoscopy
Why
Identify diverticular stigmata and alternative lesions and provide endoscopic haemostasis in a stable admitted patient.
Interpretation and limitations
Active bleeding, a visible vessel or adherent clot within a diverticulum supports attribution. Diverticula without stigmata are circumstantial, so document competing lesions and preparation quality.
05
Upper gastrointestinal endoscopy
Why
Exclude and treat an upper source when clinical clues or ongoing instability remain despite absent lower localisation.
Interpretation and limitations
Ulcer, varix or other upper lesion redirects haemostatic care. A negative examination returns attention to intermittent lower bleeding but should be interpreted with timing and quality.
06
Catheter mesenteric angiography
Why
Confirm a CT-localised bleeding artery and permit selective embolisation by interventional radiology.
Interpretation and limitations
Successful targeted embolisation controls haemorrhage while limiting bowel ischaemia risk. Continued bleeding or post-procedure pain and lactate change require urgent reassessment.

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

Colorectal cancer

Persistent altered bowel habit, iron-deficiency anaemia, weight loss or a lesion on colonoscopy argues against attributing bleeding solely to incidental diverticula.

Angiodysplasia

Fragile ectatic mucosal vessels, often in the proximal colon and associated with recurrent painless bleeding, are identified by endoscopy or angiographic imaging.

Brisk upper-GI haemorrhage

Haemodynamic instability with fresh rectal blood can reflect rapid upper-source transit; haematemesis, melaena, urea pattern and upper endoscopy help discriminate.

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

01Unstable bleedingResuscitate and localise rapidlyFirst stepHaematochezia accompanies shock, ongoing major loss or failure to respond durably to initial resuscitation.

1Begin ABCDE, two suitable venous lines, urgent bloods and crossmatch, warming, continuous observations and the local major-haemorrhage protocol when activation criteria are met.
2Call senior gastroenterology and colorectal teams, alert interventional radiology and transfusion services, and document last antithrombotic doses while analgesia and resuscitation continue.
3Arrange CT angiography promptly; if active extravasation is shown, proceed rapidly to catheter angiography and selective embolisation where available.
4If CTA is negative but instability continues, reassess for an upper source, intermittent bleeding and repeat or operative strategies through the multidisciplinary emergency team.

02Stable major bleedPrepare for inpatient diagnosis and therapyBleeding is clinically major but haemodynamic stability is sustained after initial assessment.

1Admit, monitor stool and physiology, correct fluid and clinically important anaemia, and risk-assess comorbidity and antithrombotic indication.
2Undertake adequate bowel preparation with attention to aspiration, renal and fluid risks, then arrange colonoscopy on the next available appropriate list.
3DefinitiveTreat a definite diverticular bleeding stigma using local endoscopic expertise and document whether attribution is definitive or presumptive.
4EscalationEscalate recurrent instability to CTA and interventional radiology rather than repeating ineffective unprepared endoscopy.

03After haemostasisPrevent recurrence and close the loopBleeding has stopped spontaneously or after endoscopic or radiological treatment.

1Agree anticoagulant and antiplatelet restart with the indication owner, specifying date, contingency and whether reversal or interruption changes thrombosis protection.
2Stop avoidable NSAIDs, correct iron deficiency and explain that a further painless bleed can recur and requires early reassessment if substantial.
3Ensure cancer and polyp evaluation is complete, particularly when the source was presumptive, preparation poor or warning symptoms coexist.
4DefinitiveArrange follow-up of haemoglobin, intervention complications and histology, and communicate the definitive bleeding-source confidence to primary and secondary care.

Key medicines and prescribing safety3 treatments · regimens, roles and cautions

Restores oxygen-carrying capacity when acute blood loss, symptoms and comorbidity make anaemia dangerous; it does not stop the bleeding vessel.

Red-cell transfusion

Use the current NICE restrictive threshold and target for clinically significant bleeding, individualised during exsanguination or active myocardial ischaemia under the major-haemorrhage protocol.

Avoid automatic liberal transfusion after bleeding stops. Monitor identity, reaction, volume overload, electrolytes and temperature, and pursue localisation and haemostasis simultaneously.

Reduces anticoagulant effect during critical haemorrhage while definitive radiological, endoscopic or surgical haemostasis is arranged.

Anticoagulant reversal

Use the agent-specific current hospital protocol only for life-threatening or uncontrolled bleeding after identifying the anticoagulant, last dose, renal function and indication.

Reversal carries thrombosis risk and is not a substitute for source control. INR is inadequate for DOAC effect; involve haematology and the indication owner and document restart planning.

Replenishes iron and supports haemoglobin recovery after the acute event once continuing blood loss is controlled or being investigated.

Iron replacement

After haemostasis, replace confirmed iron deficiency using the current oral regimen or an intravenous preparation when loss, intolerance or urgency makes that preferable.

Do not let iron normalise the count while the source remains unexplained. Oral therapy can darken stool or cause constipation; IV preparations need supervised administration and reaction monitoring.

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

Haemorrhagic shock

Substantial arterial loss can cause syncope, myocardial demand ischaemia, acute kidney injury and multiorgan hypoperfusion before haemoglobin equilibrates.

Anaemia and transfusion burden

Ongoing or recurrent bleeding causes symptomatic anaemia and may require transfusion, with particular risk in cardiovascular disease.

Recurrent bleeding

Recurrence can prompt repeat admission, angiographic embolisation or surgery when endoscopic localisation and haemostasis are unsuccessful.

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

During active bleeding, trend pulse, blood pressure, respiratory rate, consciousness, peripheral perfusion, urine output and visible loss at a frequency matched to instability.
Repeat haemoglobin, platelets, renal function, coagulation and electrolytes according to trajectory, remembering that fluid redistribution changes haemoglobin after presentation.
After embolisation, monitor abdominal pain, tenderness, fever, lactate and organ function for bowel ischaemia or recurrent haemorrhage.
Record every anticoagulant or antiplatelet hold, reversal and restart decision with the indication, responsible specialist and exact review point.
Follow haemoglobin and ferritin to recovery and confirm completion of colonoscopic, histological or cancer-pathway actions when source attribution was uncertain.

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

Painless can be dangerous

Diverticular arterial bleeding often lacks inflammation and pain. Absence of tenderness must not down-grade syncope, tachycardia or ongoing large-volume loss.

Haemoglobin lags haemorrhage

Whole blood is lost initially, so concentration may remain deceptively normal before redistribution or fluids. Physiological change and serial measurement lead early decisions.

CTA is a directional test

In active unstable bleeding it both identifies the bowel segment and provides a road map for selective angiographic embolisation, shortening the route to haemostasis.

Diverticula are not proof

Because diverticulosis is common, a colon containing diverticula but no bleeding stigma yields only a presumptive diagnosis. The confidence level should be stated explicitly.

Restart is part of haemostasis

Stopping antithrombotic treatment may aid immediate control but exposes the original thrombotic indication. A named restart plan prevents indefinite omission after discharge.

11Common pitfallsFrequent interpretation and management errors.

01
Waiting for haemoglobin to fall before treating a shocked patient as major haemorrhage.
02
Calling any painless rectal blood diverticular solely because a previous scan showed diverticulosis.
03
Sending an unstable patient for routine colonoscopy instead of rapid CT angiography and IR planning.
04
Ignoring a brisk upper gastrointestinal source when haematochezia accompanies haemodynamic compromise.
05
Reversing or withholding antithrombotic therapy without documenting indication ownership and restart.
06
Performing blind segmental colectomy without convincing localisation when other haemostatic routes remain.