Lower gastrointestinal bleeding

Jack Ren et al.

Lower gastrointestinal bleeding (LGIB) is defined as that occurring distal to the ligament of Treitz (i.e. from the jejunum, ileum, colon, rectum or anus) and presenting as either haematochezia (bright red blood/clots or burgundy stools) or melaena.

The incidence of LGIB is only one-fifth that of the upper gastrointestinal tract and is estimated to be ~24 per 100,000 adults per year. Male and older patients tend to suffer from more severe LGIB 3

Acute bleeding is defined as bleeding of <3 days duration resulting in instability of vital signs, anaemia and/or the need for blood transfusion 3

Chronic bleeding is defined as slow blood loss over a period of several days or longer, presenting with symptoms of occult faecal blood, intermittent melaena or scant hematochezia 3.

LGIB usually is chronic and the bleeding ceases spontaneously (80%) 3.

Aetiology

Although LGIB can occur at any age, specific disease processes are distinctive for different age groups and familiarity with this can help tailor the diagnostic workup 2,6:

See article: lower gastrointestinal bleeding (differential diagnosis).

Risk factors

Risk factors include 1

  • medications (e.g. NSAID, warfarin)
  • recent colonoscopy with polypectomy (post polypectomy bleeding)
  • prior abdominal/pelvic radiation (radiation proctitis/colitis)
  • prior surgery
  • history of alcoholism or chronic liver disease
  • history of abdominal aortic aneurysm with or without surgical repair (i.e. causing an aortoenteric fistula)

Colonoscopy is the first-line investigation of both diagnostic and therapeutic management. CT angiography (CTA), nuclear medicine studies, and angiography can all be used to assess LGIB but have limited sensitivity when bleeding rates are intermittent or slow. Below are the estimated detectable rates of bleeding by modality 5,6:

  • nuclear medicine: ≤0.1 mL/min
  • CT angiography: ≥0.35 mL/min
  • angiography: ≥0.5 mL/min

CTA and 99mTc-labeled RBC scintigraphy have equal rates of detection of LGIB (at ~40% in one series), but CTA appears to have higher localisation rates 7.

CT

CTA provides a relatively non-invasive and effective way of localising the source of bleeding, especially in the patient with continued bleeding 5.

Studies have looked at the use of CTA in the localisation of GI haemorrhage report sensitivity of ~90% when there is active bleeding but are considerably lower when the bleeding is intermittent in nature with rates reported at ~45% 1.

Again, contraindications apply to patients with renal failure who are at risk of developing contrast-induced nephropathy 1.

Nuclear medicine

Erythrocytes are labelled with technetium-99m and then serial scintigraphy is performed (a.k.a. 99mTc-labeled RBC scintigraphy / tagged red blood cell scan) to detect focal collections of radiolabelled material. It can be performed relatively quickly and may help localise the general area of active bleeding to guide subsequent endoscopy, angiography or surgery 1

A false-positive result can be produced by a rapid transit of luminal blood so that labeled blood is detected in the colon even though it originated from a more proximal site in the GIT 1

Angiography

In patients with lower GI bleeding who are haemodynamically stable and do not have ongoing fresh per rectal bleeding, an RBC-labeled Tc99m scan is recommended as a first line of investigation. Catheter angiography is recommended in patients with time to positive (TTP) of 9 min or less. If TTP is more than 9 min, the likelihood of detecting the bleeding site on angiogram will be markedly low.

Angiography can provide the opportunity for therapeutic intervention at the time of diagnosis 1-2. However, the bleeding rate must be ≥ 0.5 mL/min to detect extravasation into the gut, which is significantly higher than in nuclear medicine. Additionally, certain patient factors (e.g. contrast allergy, acute/chronic kidney disease) are potential contraindications to angiography 1

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Article Information

rID: 29000
Section: Pathology
Synonyms or Alternate Spellings:
  • Lower GI bleeding
  • Acute colonic bleeding
  • LGBI
  • Lower GI hemorrhage
  • Lower gastrointestinal haemorrhage
  • Lower GI haemorrhage
  • Lower gastrointestinal hemorrhage

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Cases and Figures

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    Case 2: angio-embolisation
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    Case 3
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    Case 4: diverticular haemorrhage
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    Case 5: jejunal bleed and embolisation
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    Case 6: proximal colon active bleeding
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    Case 7: small bowel vascular angioectasia
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    Case 8: colonic bleed treated with embolisation
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    Case 9: colonic diverticular haemorrhage
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