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 is usually chronic and the bleeding usually ceases spontaneously (80%) 3.
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:
- adolescents and young adults
- older adults
See article: lower gastrointestinal bleeding (differential diagnosis).
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 (causing an aortoenteric fistula)
Colonoscopy is the first-line investigation for 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 is 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-labelled RBC scintigraphy have equal rates of detection of LGIB (at ~40% in one series), but CTA appears to have higher localisation rates 7.
CTA provides a relatively non-invasive and effective way of localising the source of bleeding, especially in patients with continuous bleeding 5.
Studies that have evaluated the use of CTA in the localisation of gastrointestinal haemorrhage report a sensitivity of ~90% when there is active bleeding, with detection rates steeply falling to ~45% when the bleeding is intermittent 1.
Again, contraindications apply to patients with renal failure who are at risk of developing contrast-induced nephropathy 1.
Erythrocytes are labelled with technetium-99m, then serial scintigraphy is performed (a.k.a. 99mTc-labeled RBC scintigraphy or 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 gastrointestinal tract 1.
In patients with lower gastrointestinal bleeding who are haemodynamically stable and do not have ongoing fresh 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 minutes or less. If TTP is over 9 minutes, the likelihood of detecting the site of bleeding on an 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.
- 1. Ghassemi KA, Jensen DM. Lower GI bleeding: epidemiology and management. Curr Gastroenterol Rep. 2013;15 (7): 333. doi:10.1007/s11894-013-0333-5 - Free text at pubmed - Pubmed citation
- 2. Raphaeli T, Menon R. Current treatment of lower gastrointestinal hemorrhage. Clin Colon Rectal Surg. 2012;25 (04): 219-27. doi:10.1055/s-0032-1329393 - Free text at pubmed - Pubmed citation
- 3. Jang BI. Lower Gastrointestinal Bleeding: Is Urgent Colonoscopy Necessary for All Hematochezia?. Clin Endosc. 2013;46 (5): 476-479. doi:10.5946/ce.2013.46.5.476 - Free text at pubmed - Pubmed citation
- 4. Mariani G, Pauwels EK, AlSharif A et-al. Radionuclide evaluation of the lower gastrointestinal tract. J. Nucl. Med. 2008;49 (5): 776-87. doi:10.2967/jnumed.107.040113 - Pubmed citation
- 5. Geffroy Y, Rodallec MH, Boulay-Coletta I et-al. Multidetector CT angiography in acute gastrointestinal bleeding: why, when, and how. Radiographics. 2011;31 (3): E35-46. doi:10.1148/rg.313105206 - Pubmed citation
- 6. Brant WE, Helms C. Fundamentals of Diagnostic Radiology. Lippincott Williams & Wilkins. ISBN:1608319121. Read it at Google Books - Find it at Amazon
- 7. Feuerstein JD, Ketwaroo G, Tewani SK et-al. Localizing Acute Lower Gastrointestinal Hemorrhage: CT Angiography Versus Tagged RBC Scintigraphy. AJR Am J Roentgenol. 2016; 1-7. doi:10.2214/AJR.15.15714 - Pubmed citation