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Lower Gastrointestinal Bleeding: Advances in Diagnosis and Management

M3 India Newsdesk Dec 29, 2023

This article delves into Lower Gastrointestinal Bleeding (LGIB), detailing its causes, clinical manifestations, initial evaluation, and diagnostic studies. It emphasises the importance of timely identification and localisation of bleeding sources for appropriate intervention.

Lower Gastrointestinal Bleeding (LGIB)

Lower gastrointestinal bleeding (LGIB) theoretically encompasses all bleeds that originate from the GI tract beyond the ligament of Trietz i.e., from the beginning of the jejunum to the anus. However, practically most of them originate from the colon.

  1. LGIB is approximately one-fifth as common as upper GI bleed (UGIB). The incidence and risk of lower GI bleeding increases with age, with a 200-fold rise in incidence from the third decade to the ninth decade of life.
  2. Multiple hypotheses have been put forward for this increase, presumably due to the increasing incidence of diverticulosis, malignancies, ischemic diseases involving the bowel, and drug use in the later part of life.
  3. Acute LGIB is arbitrarily defined as bleeding of fewer than 3 days in duration that may result in instability of vital sign anaemia, and/or need for blood transfusion.
  4. Chronic LGIB involves any bleeds from the LGI tract over several days, weeks or months. Patients with chronic bleeding can also have occult faecal blood loss presenting as anaemia and is diagnosed as LGIB only when investigated.

Clinical manifestations

A typical manifestation of LGIB is hematochezia (passage of maroon or bright red blood or blood clots per rectum). Blood originating from the left colon tends to be bright red, whereas bleeding from the right side of the colon usually appears dark or maroon coloured and may be mixed with stool.

Rectal passage of minimal bright red blood most commonly occurs in a chronic intermittent pattern and has also been referred to as "intermittent scant hematochezia".

The term minimal bright red blood per rectum (BRBPR) indicates a few drops of blood in the toilet bowl after defecation. Small amounts of blood on the surface of the stool are also considered minimal BRBPR.

A history of minimal BRBPR suggests a lesion near the anal canal. Benign etiologies of BRBPR are common and appear to account for 90 per cent or more of all episodes of minimal BRBPR. However, scant rectal bleeding is also a common presenting symptom of serious diagnoses, such as colorectal cancer.

Rarely, slow-rate bleeding from the right side of the colon as well as the small bowel will present with melena.

Initial evaluation and management

The goals of evaluation are to determine if the bleeding is coming from the lower GI tract, determine the severity of bleeding, triage patients to the appropriate setting, provide general supportive measures, and initiate resuscitation.

Supportive measures and resuscitation in the setting of LGIB are more or less similar to any other GI bleed and have been covered in the first part of this series.

Initial evaluation

1. History

  1. Patients should be asked about prior episodes of GI bleeding, and the use of medications such as NSAIDs, anti-coagulants and antiplatelet agents.
  2. Patients should also be asked about symptoms that may suggest a particular aetiology for the bleeding (eg, painless hematochezia with diverticular bleeding, change in bowel habits with malignancy, abdominal pain with colitis).
  3. A history of abdominal pain suggests the presence of an inflammatory bleeding source such as ischemic or infectious colitis.

2. Physical examination

The physical examination should include an assessment of hemodynamic stability as well as an examination of the patient's stool to confirm the presence of hematochezia or melena.

3. Laboratory tests 

Laboratory tests that should be obtained in patients with acute GI bleeding include a complete blood count, liver and renal function tests, and coagulation profiles. The initial haemoglobin level should be monitored every twelve hours, depending on the severity of the bleed.

4. Consider an upper GI bleeding source

  1. The primary consideration in the differential diagnosis of hematochezia is upper GI bleeding since 10 to 15 per cent of patients with severe hematochezia will have an upper GI source.
  2. Findings that are suggestive of an upper GI source include hemodynamic instability, orthostatic hypotension, and an elevated blood urea nitrogen (BUN)-to-creatinine or urea-to-creatinine ratio (>20 to 30:1 or >100:1, respectively).
  3. The presence of blood clots in the stool decreases the likelihood of an upper GI source. If the index of suspicion for an upper GI source is high, an upper endoscopy should be performed once the patient is appropriately resuscitated.

5. Triage

Several studies have identified clinical features that predict the risk of complications in patients with presumed acute lower GI bleeding. These features can be used to help categorise patients as either low or high-risk.

High-risk features include:

  • Hemodynamic instability (hypotension, tachycardia, orthostasis, syncope)
  • Persistent bleeding
  • Significant comorbid illnesses
  • Advanced age
  • Bleeding that occurs in a patient who is hospitalised for another reason
  • A prior history of bleeding from diverticulosis or angiodysplasia
  • Current aspirin use
  • Prolonged prothrombin time
  • Hypoalbuminemia
  • A non-tender abdomen
  • No diarrhoea
  • Anaemia
  • An elevated blood urea nitrogen level
  • An abnormal white blood cell count

The number of high-risk features present correlates with the likelihood of a poor outcome.

The shock index (heart rate/systolic blood pressure) is a tool to identify unstable patients with GI bleeding. Patients with an index of >1 may be considered for initial evaluation with a computed tomography (CT) angiography.

Outpatient management may be appropriate for some low-risk patients (eg, a young, otherwise healthy patient with minor, self-limited rectal bleeding and no hemodynamic compromise).

Risk stratification tools can be used to supplement clinical judgment to help identify low-risk patients. The extent of evaluation (flexible sigmoidoscopy versus colonoscopy) in these patients depends, at least in part, upon the patient's age.

6. Oakland score

A composite score based on age, sex, prior history of lower GI bleeding, presence of blood on rectal exam, heart rate, systolic blood pressure, and haemoglobin concentration is used to determine safe discharge. A score of ≤8 predicted a 95 per cent probability of safe discharge.

Diagnostic studies


Colonoscopy is the diagnostic test of choice for hemodynamically stable patients with a lower GI bleed.

Advantages of colonoscopy compared with other tests for lower GI bleeding include:

  1. It has the potential to precisely localise the site of the bleeding regardless of the aetiology or rate of bleeding.
  2. The ability to collect pathologic specimens.
  3. The potential for therapeutic intervention.

Disadvantages of colonoscopy include:

  1. The need for bowel preparation, and poor visualisation in an unprepared or poorly prepared colon.
  2. The risks of sedation in an acutely bleeding patient.
  3. Complications are reported in fewer than 2 per cent of colonoscopies performed for lower GI bleeding.

Aggressive lavage may be needed to localise the bleeding site. The terminal ileum should be inspected to rule out bleeding from a proximal lesion in the small bowel.

The use of a clear cap on the tip of the colonoscope can assist in the detection and treatment of bleeding. A definitive or potential bleeding source is visualised in 45 to 90 per cent of patients undergoing colonoscopy for lower GI bleeding.

The identification of more than one potential bleeding site is common (eg, diverticulosis and haemorrhoids). Furthermore, a bleeding site is not always identified.

Colonoscopy should be performed on a next available day basis during their hospitalisation after adequate colon preparation in patients presenting with lower GI bleeding.

An unprepared evaluation should be reserved for lower GI bleeding when the source is highly suspected or known to be in the anorectal area or distal colon.

An approach using water-jet pumps and mechanical suction devices ("hydro flush colonoscopy") has been described as an alternative to administering a bowel preparation.

Radiographic imaging

  1. An advantage of all radiographic tests for GI bleeding is the ability to diagnose bleeding throughout the GI tract, including small bowel sources. However, these studies all require active bleeding at the time of the study to detect a bleeding site.
  2. In patients with severe bleeding who cannot be stabilised for colonoscopy or with severe ongoing bleeding despite colonoscopy, CT angiography may be used to select patients with active bleeding for subsequent angiography or, less commonly, to localise the source before surgery.
  3. Angiography must be performed promptly after a positive CT angiography (ideally within 90 minutes).

CT angiography 

  1. In patients with ongoing hemodynamically significant hematochezia, CT angiography is the initial diagnostic test of choice.
  2. CT angiography is widely available, fast, and minimally invasive.
  3. In addition, it provides anatomic detail that may be helpful for subsequent interventions such as angiography. Bleeding at a rate of 0.3 to 0.5 mL/minute can be detected with CT angiography.
  4. CT angiography is typically performed using multidetector row helical CT.


  1. The advantages of angiography over other tests for lower GI bleeding are that it does not require bowel preparation and anatomic localisation is accurate. It also permits therapeutic intervention.
  2. Transcatheter embolisation is a means of controlling haemorrhage and has largely replaced other temporising interventions such as vasopressin infusion. Superselective embolisation of distal vessels using coaxial catheters decreases the risk of bowel infarction.

Radionuclide imaging

  1. It has limited accuracy in identifying the location of the bleeding site and logistical constraints. Radionuclide scanning detects bleeding that is occurring at a rate of 0.1 to 0.5 mL/minute, and it is the most sensitive radiographic test for GI bleeding. However, a major disadvantage of radionuclide imaging is that it can only localise bleeding to a general area of the abdomen.
  2. Accuracy rates have varied substantially across reports, ranging from 24 to 91 per cent.
  3. Poor localisation occurs because blood can move in either a peristaltic or antiperistaltic direction. In addition, localisation to an area of the abdomen is not equivalent to identifying a specific site.

Additional testing if the bleeding site is not identified

  1. A bleeding site may not be evident in some patients despite lower GI evaluation.
  2. If not already done, upper endoscopy or push enteroscopy should be considered in those with severe, ongoing bleeding since up to 15 per cent of such patients have a bleeding site in the upper digestive tract.
  3. Push enteroscopy (endoscopy using a pediatric colonoscope or a dedicated enteroscope) allows visualisation of approximately the proximal 60 cm of the jejunum. Other methods to evaluate the small intestine, include capsule endoscopy and deep small bowel enteroscopy.
  4. In some patients, bleeding may have stopped, making efforts to identify the site more difficult. Such patients should be observed for 24 to 48 hours. An urgent CT angiogram/tagged red blood cell scan can be obtained to localise the region of bleeding if bleeding resumes.

Treatment of the bleeding site

The treatment of lower gastrointestinal (GI) bleeding depends on the source of the bleeding. In many cases, the bleeding can be controlled with therapies applied at the time of colonoscopy or angiography.

Rarely, patients with massive LGIB will need immediate surgery. The morbidity and mortality associated with colectomy in the absence of preoperative localisation of a bleeding site are higher than in patients who have a bleeding site identified before surgery. Thus, all efforts should be made to identify the bleeding source before surgery.

In patients with significant, early (during the initial hospitalisation) recurrent lower gastrointestinal bleeding, a repeat colonoscopy should be performed with endoscopic hemostasis if indicated.

Factors associated with rebleeding include:

  • The presence of underlying comorbidities
  • Antiplatelet/anticoagulant/NSAID use
  • Source of bleeding
  • The initial modality of hemostasis


Click here to read Upper Gastrointestinal Bleeding: Advances in Diagnosis and Management


Disclaimer- The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or position of M3 India.

About the author of this article: Dr Parag Dashatwar is a DNB gastroenterologist, who leads the department of medical gastroenterology at Olive Hospital, Hyderabad.

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