01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Rectal bleeding ranges from minor anal-canal trauma to haemorrhage that threatens circulating volume. A useful history distinguishes blood on wiping, coating the stool, mixed through stool or passed independently, but these patterns alter probability rather than proving anatomical origin. Haemodynamic observations, perfusion and repeated clinical assessment determine urgency.
Finding a fissure or haemorrhoids can explain some bleeding, yet it does not account automatically for weight loss, persistent bowel-habit change, iron deficiency or a palpable rectal lesion. The plan must therefore state which benign finding is being treated, which colorectal risks remain, and how FIT or structural investigation will reach completion.
Key points
- Resuscitate before localisation when rectal bleeding causes shock or continuing circulatory compromise.
- Describe whether blood coats or mixes with stool, its volume, pain, recurrence and associated mucus.
- Weight loss, bowel-habit change, abdominal pain, iron deficiency or a mass require colorectal cancer assessment.
- Inspect the anus and perform consented digital rectal examination, recognising that the finger cannot assess the whole colon.
- Offer quantitative FIT within current NICE symptom criteria; do not let a low result override a rectal mass or strong concern.
- Track haemoglobin, referral, endoscopic or radiological completion and histology until the source is established.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Anorectal disease
Haemorrhoids, fissure, proctitis and trauma commonly produce fresh bleeding; pain, prolapse, discharge and examination help distinguish them.
Colorectal pathology
Cancer, adenomas, diverticular disease, inflammatory bowel disease, angioectasia and colitis can bleed, sometimes intermittently and without localising pain.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Mucosal disruption
Ulceration, inflammation or neoplastic friability exposes small vessels, so bleeding may be intermittent and mixed with mucus or stool.
- 2Vascular rupture
Diverticula and angioectasia can open an arterial or ectatic vessel and cause brisk painless bleeding without preceding mucosal inflammation.
- 3Systemic consequence
Loss exceeding compensatory reserve reduces circulating volume and tissue perfusion; chronic occult loss instead depletes iron stores before haemodynamic signs appear.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Bright blood on paper or coating stool suggests a distal source, whereas blood mixed through stool or maroon output raises concern for a more proximal lesion; colour alone cannot localise reliably.
Pain with defaecation points toward fissure, painless bleeding and prolapse toward haemorrhoids, while altered bowel habit, weight loss, abdominal pain or iron deficiency heighten concern for colorectal cancer.
Ask about anticoagulants, antiplatelets, non-steroidal anti-inflammatory drugs, liver disease and previous pelvic radiotherapy because they modify severity and the differential.
A digital rectal examination can identify a low rectal mass, melaena, impacted stool or tenderness, but a normal examination does not exclude colorectal neoplasia.
Visible haemorrhoids do not automatically explain anaemia, persistent bleeding or alarm features; two conditions can coexist.
05InvestigationsWhat to request, why it matters and how to interpret it.
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
ABCDE observations and full blood countFirst step - Why
- quantify immediate physiological impact and obtain a baseline haemoglobin and platelet count
- Interpretation and limitations
- An early haemoglobin may remain normal after acute loss; interpret it with perfusion, trajectory and repeated measurement.
- 02
Digital rectal examination and proctoscopy when appropriate - Why
- identify palpable rectal or visible anal canal pathology after consent
- Interpretation and limitations
- A negative limited examination does not assess the proximal rectum or colon and cannot close an alarm-feature pathway.
- 03
Quantitative faecal immunochemical test - Why
- estimate the likelihood of colorectal bleeding in the NICE symptomatic pathway
- Interpretation and limitations
- Use the numerical result with symptoms and safety-netting; a result below threshold does not overrule a rectal mass, unexplained anal mass or persistent strong clinical concern.
- 04
Colonoscopy or CT colonography selected by the diagnostic service - Why
- evaluate the colon when referral criteria, anaemia or persistent symptoms require structural investigation
- Interpretation and limitations
- Colonoscopy permits biopsy and polypectomy; CT colonography is less invasive but a positive lesion generally still needs endoscopic tissue diagnosis.
- 05
Coagulation, renal and liver profiles with group-and-save when bleeding is important - Why
- identify correctable contributors and prepare for transfusion or intervention
- Interpretation and limitations
- Results inform risk and treatment but must not delay resuscitation in a patient with ongoing circulatory compromise.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Upper gastrointestinal bleeding
Rapid upper-tract bleeding can present as haematochezia, especially with shock; melaena, haematemesis and urea pattern provide supporting context.
Gynaecological or urinary bleeding
Blood noticed in the toilet may come from another tract, so a careful history and directed examination prevent mislocalisation.
Food or pigment
Beetroot and other pigments can mimic blood, but a plausible dietary history must not end assessment when physiological or alarm features exist.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Worked case: applied assessment of rectal bleedingReach a specific decision and confirm it happenedFirst stepA 58-year-old has six weeks of painless blood mixed with looser stool. Examination finds small non-bleeding haemorrhoids but no rectal mass; haemoglobin is 111 g/L and quantitative FIT is 28 micrograms haemoglobin per gram.+
- 1Confirm stable observations and no current heavy bleeding, then quantify the duration, blood-stool relationship, weight change, family history, medicines and previous colorectal investigation.
- 2Record the non-bleeding haemorrhoids without treating them as the complete explanation; a normal low-rectal examination cannot assess the proximal rectum or colon.
- 3Interpret 28 micrograms per gram as above the NICE symptomatic threshold of 10 and submit a suspected colorectal-cancer pathway referral with the numerical value and anaemia.
- 4Colonoscopy identifies a 3 cm sigmoid lesion and biopsies confirm adenocarcinoma; arrange staging rather than continuing haemorrhoid treatment alone.
- 5Verify staging and colorectal multidisciplinary review, and give immediate return advice for syncope, large-volume recurrent bleeding, distension or vomiting.
02Stable anorectal patternTreat a demonstrated distal source without losing the safety-netA 31-year-old has sharp pain during defaecation and a small streak of blood on paper; inspection shows a posterior fissure, with no bowel-habit change, weight loss, anaemia or mass.+
- 1Treat constipation and fissure symptoms, review contributing medicines and explain that healing should reduce both pain and bleeding.
- 2Do not instrument the acutely painful anal canal merely to complete a routine; use follow-up and further colorectal assessment if the diagnosis becomes uncertain.
- 3Verify healing and resolution of bleeding at the agreed review; persistent blood, iron deficiency or new alarm features reopens the colorectal diagnostic pathway.
03Active haemorrhage pathwayResuscitate and localise continuing major bleedingAn anticoagulated 76-year-old passes repeated maroon stool, becomes confused and clammy, and has blood pressure 84/50 mmHg despite initial fluid.+
- 1Activate the major-haemorrhage response, provide oxygen as indicated, obtain two large-bore cannulas, full blood count, coagulation, renal profile and crossmatch, and give warmed blood components according to physiology and protocol.
- 2Assess whether brisk upper-GI bleeding could explain haematochezia and make a senior antithrombotic-reversal decision from the drug, last dose, renal function and thrombotic indication.
- 3Arrange urgent CT angiography to localise continuing bleeding; a positive result should prompt rapid interventional-radiology embolisation assessment, with surgery involved if endoscopic or radiological control fails.
- 4Verify haemostasis through repeated observations, stool output, transfusion need and haemoglobin trend, then document when and by whom antithrombotic therapy will restart.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Hypovolaemia
Ongoing brisk loss can progress from tachycardia to hypotension, organ hypoperfusion and collapse unless bleeding is controlled promptly.
Iron deficiency
Repeated small-volume loss may produce depleted ferritin, microcytosis and symptomatic anaemia with fatigue and impaired exercise tolerance.
Delayed cancer diagnosis
Premature attribution to benign anorectal disease can postpone investigation of a proximal or rectal malignancy before definitive tissue diagnosis is obtained.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Document whether bleeding has stopped, recurred or changed in volume, and repeat observations after any resuscitation rather than relying on one reassuring set.
- Track haemoglobin and iron indices according to acuity; continued decline after apparent cessation suggests ongoing or recurrent loss.
- Confirm that FIT sampling, referral and definitive colonic investigation have actually occurred and that histology is reviewed by the responsible team.
- After identifying haemorrhoids or fissure, reassess if bleeding persists, anaemia develops or bowel habit changes because the initial explanation may be incomplete.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Blood pattern is probabilistic
Blood coating stool supports an anorectal source but does not prove it; transit and bleeding rate alter colour, and proximal disease may still present with fresh blood.
Examination has a limited field
A careful digital examination adds high-value information about low lesions and stool, yet its anatomical reach is short and should be described honestly.
FIT is a triage test
Quantitative FIT changes cancer probability and referral priority; it is not a universal rule-out test and must sit within clinical assessment and safety-netting.
Medication review changes risk
Antithrombotic treatment may worsen bleeding but should not be labelled the anatomical cause, and interruption decisions require assessment of thrombosis risk.
11Common pitfallsFrequent interpretation and management errors.
- 01
Attributing recurrent bleeding to haemorrhoids without investigating coexisting alarm features can delay a colorectal cancer diagnosis.
- 02
Using a single normal haemoglobin to dismiss substantial recent blood loss ignores haemodilution and the time course of laboratory change.
- 03
Performing intimate examination without clear consent, adequate privacy or an offered chaperone undermines both safety and diagnostic quality.
- 04
Treating a low FIT result as permission to ignore a rectal mass or persistent unexplained symptoms misapplies the symptomatic pathway.