Lower gastrointestinal bleeding causes

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

Causes

Common causes

• Colonic diverticulosis
  • Colonic diverticulosisis the most common cause of acute LGIB in the western world, accounting for 15% to 55% of all LGIB
  • Diverticula can occur anywhere in the gastrointestinal tract, but are most common in the sigmoid colon. However, approximately 60% of diverticular bleeds arise from diverticula in the right colon, highlighting a tendency for right-sided diverticula to bleed
  • Hemorrhage results from rupture of the intramural branches (vasa recta) of the marginal artery at the dome of a diverticulum and can give rise to a massive, life-threatening LGIB
  • This is by far the most common cause of bleeding in the elderly, as the prevalence of diverticular disease increases with age, being as high as 85% by the age of 85 years

• Obesity has recently been recognized as a risk factor in the development of diverticular disease, and the risk of diverticular bleeding in this group of patients is higher than that in patients who are not obese
• Vascular ectasias (angiodysplasias/angioectasias):
  • Tortuous dilated submucosal vessels that account for approximately 10% of LGIB.
  • They appear endoscopically as small, flat lesions (5-10 mm) with ectatic capillaries radiating from a central vessel (Fig. 1)
  • The prevalence of angiodysplasia in the gastrointestinal tract is not well known, but a pooled analysis of three colonoscopic cancer screening studies detected angiodysplasia in 0.8% of the patients The prevalence of angiodysplasia is higher in older populations and, in the past, has been linked to certain conditions such as end-stage renal disease, Von Willebrand disease , and aortic stenosis In one series, 37% of colonic dysplasias were found in the cecum, 17% in the ascending colon, 7% in the transverse colon, 7% in the descending colon, and 32% in rectosigmoid area
  • Angiodysplasia can also be found throughout the small bowel and is responsible for up to 40% of small intestinal bleeding in patients older than 40 years.
  • Angiodysplasia of the stomach and duodenum is responsible for up to 7% of UGIB I
• Iatrogenic:
  • Bleeding is recognized as the most common complication of colonoscopy and polypectomy, occurring in 0.3% to 6.1% of polypectomies
  • Risk factors for bleeding include polyp size greater than 1 cm, patient age older than 65 years, presence of comorbid disease, and polypectomy using the cutting mode of current
  • The risk is also greater in patients taking anticoagulant or antiplatelet agents
• Ischemic colitis:
  • Ischemic colitis accounts for approximately 20% of LGIB
  • Ischemia results from a sudden reduction in blood flow to the mesenteric vessels as a result of hypotension, occlusion, or spasm of the mesenteric vessels
  • Nonocclusive disease typically affects the watershed areas of the bowels, such as the splenic flexure and adjacent transverse colon due to the poor blood supply from the marginal artery.
  • Occlusive disease is rarer but can occur as a result of thrombus formation or embolus.
  • It is a recognized complication of aortic surgery
  • Elderly patients with comorbid disease are at higher risk of developing ischemic colitis.
  • There may be a history of ischemic heart disease
  • The majority of patients with ischemic colitis improve following conservative management; however, approximately 20% will progress to develop colonic gangrene
  • Other complications include chronic colitis and stricture formation
  • Diagnosis requires a high index of suspicion
• Colorectal malignancy:
  • Colorectal cancer accounts for approximately 10% of bleeds, either as occult bleeding presenting with anemia or as frank blood loss per rectum
  • A family history of colorectal cancer is important to establish
• Anorectal abnormalities:
  • Hemorrhoids, fissures, fistulae, and polyps can all present with bright red rectal bleeding, which may be intermittent in nature
  • Hemorrhoids are the most common cause of rectal bleeding in adults younger than 50 years
  • The finding of hemorrhoids in older patients with LGIB should not preclude further investigation, as hemorrhoids are an extremely common finding and may not be the cause of bleeding
• Inflammatory bowel disease (IBD):
  • IBD refers to both Crohn disease and ulcerative colitis Accounts for 5% to 10% of bleeds.
  • It is by far the most common cause of LGIB in Asian populations in whom the prevalence of diverticular disease is much lower
  • A previous history of IBD in patients with LGIB is important, as these patients have a higher risk of developing colorectal malignancy than do the general population
• Infectious colitis:
  • The most common organisms in the U.S. are species ofSalmonella,Campylobacter,Shigella, andYersinia