What are the causes of massive lower gastrointestinal bleeding (LGIB)?

Causes of Massive Lower Gastrointestinal Bleeding

The most common causes of massive lower gastrointestinal bleeding (LGIB) include diverticulosis (accounting for approximately 30% of cases), angiodysplasia, neoplasms, inflammatory bowel disease, ischemic colitis, and anorectal disorders. 1, 2

Definition of Massive LGIB

Massive LGIB is characterized by:

• Bleeding of recent duration originating beyond the ligament of Treitz 3
• Passage of large volume of red or maroon blood through the rectum 3
• Hemodynamic instability and shock 3
• Initial decrease in hemoglobin level of 6 g/dL or more 3
• Requirement for transfusion of at least 2 units of packed red blood cells 3
• Bleeding that continues for 3 days or significant rebleeding within 1 week 3

Common Etiologies

Diverticulosis

• Most frequent cause, accounting for approximately 30% of cases 1
• Approximately 75% of episodes of acute lower GIB due to diverticulosis stop spontaneously 1
• More common in elderly patients 4

Angiodysplasia

• Vascular malformations that can cause intermittent or massive bleeding 2
• More common in elderly patients and those with chronic renal failure 4

Neoplasms

• Colorectal cancer and polyps can present with massive LGIB 2
• Empirical embolization for tumor bleeding has shown clinical success rates of 68%, increasing to 98% in the context of acute bleeding 1

Inflammatory Bowel Disease (IBD)

• Massive, life-threatening LGIB is uncommon in IBD patients, occurring in less than 6% of cases 1
• In ulcerative colitis, bleeding typically occurs in patients with pancolitis from diffuse areas of mucosal ulceration 1
• In Crohn's disease, bleeding most often results from focal erosion into an intestinal vessel, potentially including the small bowel 1, 5

Ischemic Colitis

• Can present with sudden onset of abdominal pain followed by bloody diarrhea 4
• More common in elderly patients with underlying vascular disease 4

Anorectal Disorders

• Hemorrhoids account for approximately 14% of LGIB cases 6
• Anorectal causes account for approximately 16.7% of LGIB diagnoses 7

Rare Causes

• Dieulafoy's lesion of the colon - a rare but potentially life-threatening cause of massive LGIB 3
• Aortoenteric fistula - an uncommon but serious cause that may justify proceeding directly to surgery 1

Risk Factors for Severe Outcomes

• Presence of hypotension on arrival at the emergency department is a significant prognostic factor for requiring urgent surgery 8
• Associated comorbidities increase the risk of morbidity and mortality 8
• Advanced age is associated with increased mortality 4
• Intestinal ischemia as a cause of bleeding carries higher mortality 4
• Hemodynamic instability is associated with worse outcomes 4

Diagnostic Approach for Massive LGIB

• For hemodynamically unstable patients, CT angiography (CTA) should be the first-line investigation to rapidly localize the bleeding site 6
• CTA is preferred over colonoscopy in unstable patients as it requires no bowel preparation and can identify bleeding sources in the upper GI tract or small bowel 6
• For stable patients, direct anorectal inspection with anoscopy should be performed first, especially with bright red rectal bleeding 6
• Approximately 10-15% of apparent LGIB may have an upper GI source, so upper GI endoscopy should be considered if CTA is negative 6

Management Considerations

• Patients should receive intravenous fluid/blood product resuscitation with the goal of normalizing blood pressure and heart rate prior to endoscopic evaluation/intervention 1
• Packed red blood cells should be transfused to maintain hemoglobin above 7g/dL, with a threshold of 9g/dL in patients with massive bleeding, significant comorbidities, or possible delay in therapeutic interventions 1
• Restrictive RBC transfusion thresholds (Hb trigger 70 g/L and target 70-90 g/L) should be used in clinically stable patients, unless they have cardiovascular disease (trigger 80 g/L, target 100 g/L) 1
• No patient should proceed to emergency laparotomy unless every effort has been made to localize bleeding by radiological and/or endoscopic modalities 1

By understanding the common causes and risk factors for massive LGIB, clinicians can better prioritize diagnostic approaches and implement timely interventions to reduce morbidity and mortality.