Rectal Bleeding in Adults

Differential Diagnosis

Common Diagnoses

Occasional Diagnoses

Rare Diagnoses

  • Blood Clotting Disorders (Including Anticoagulants)
  • Bowel Ischaemia
  • Angiodysplasia
  • Intussusception

Ready Reckoner

Key distinguishing features of the most common diagnoses

PilesFissureGastroenteritisCancer of RectumDiverticulosis
Blood and Stool MixedNoNoYesNoPossible
Abdominal PainNoNoYesNoPossible
Mass Felt PRPossibleNoNoYesPossible
Sentinel anal Skin TagNoYesNoNoNo

Possible Investigations


Possible:FBC, ESR/CRP, LFTs, bone biochemistry, U&E, stool for microbiology and faecal calprotectin, FIT, hospital-based lower GI investigations.

Small Print:Clotting screen.

  • FBC: Check for anaemia from acute or chronic bleeding; low platelets may cause or aggravate bleeding
  • ESR/CRP raised in active inflammatory bowel disease and malignancy
  • If malignancy is suspected, LFT, U&E and bone biochemistry are useful early on as a baseline
  • Clotting screen: If clotting disorder a possibility; INR if on warfarin.
  • Stool specimen: Helpful in the presence of diarrhoea. May show evidence of infective cause (especially Campylobacter) or white cells in inflammatory bowel disease. Faecal calprotectin may be useful in diagnosing IBD. FIT: A useful colorectal cancer ‘rule out’ test in patients at low risk, also commonly required when arranging a two-week referral to help secondary care stratify urgency of investigation.
  • Proctoscopy: Helpful in primary care in visualising haemorrhoids and proctitis to confirm a clinical diagnosis.
  • Hospital-based lower GI investigations: Necessary if significant pathology is suspected.

Top Tips

  • Eighty percent of rectal tumours are within fingertip range. Always do a PR examination unless the diagnosis is manifestly obvious from the history.
  • If blood is on the toilet paper and surface of the motions, the cause is likely to be palpable PR or visible on proctoscopy; if mixed in with the motions, referral for further investigation will be required to make a definite diagnosis.
  • In young adults, the diagnosis is usually clear from the history and is likely to be haemorrhoids or a fissure. In such cases, if and when you refer, to allay anxiety, emphasise that this is for treatment rather than investigation.
  • The presence of diarrhoea with rectal bleeding in young adults suggests gastroenteritis (especially Campylobacter) or colitis.

Red Flags

  • Change of bowel habit and weight loss with rectal bleeding are ominous symptoms which should prompt urgent referral.
  • Any patient aged 50 or over with unexplained rectal bleeding merits urgent referral to rule out cancer.
  • The presence of haemorrhoids does not necessarily clinch the diagnosis – another lesion may be present, especially in the elderly.
  • A brisk, painless haemorrhage in an elderly patient is likely to be caused by diverticular disease. Significant amounts of blood can be lost, so assess urgently with a view to admission
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