2015年12月翻译大赛

Hemorrhoids

  Hemorrhoids are a plexus of dilated arteriovenous vessels that arise from the superior and inferior hemorrhoidal veins. These plexuses are located in the submucosa of the distal rectum and are classified as internal or external, based on their location relative to the dentate line.11,69 Although hemorrhoids may be present in up to 75% of patients with LGIB, the majority are considered incidental findings.9 Hemorrhoidal bleeding has been reported to account for only 2% to 10% of acute LGIB.8,45 However, two recent studies found that hemorrhoids were the underlying etiology in 24% to 64.4% of patients presenting with hematochezia.25,70 Patients typically present with painless, intermittent, scant hematochezia characterized by bright red blood on the toilet paper, coating the stool, or dripping into the toilet bowl.11 Anorectal disorders, including hemorrhoids, are discussed in another ASGE guideline.69

Colorectal neoplasia

  Clinical features of bowel habit changes and weight loss should raise suspicion for a colorectal neoplasia and prompt colonoscopy in patients with LGIB. Colorectal neoplasia accounts for up to 17% of all etiologies in pa- tients with LGIB and presents more commonly with occult bleeding.8,10,71,72 Acute LGIB associated with colorectal neoplasia usually results from surface ulcerations of an advanced tumor.11 Patients with tumors in the right side of the colon are more likely to present with occult blood loss and iron deficiency anemia, whereas those with left- sided tumors more commonly present with hematochezia.71 Endoscopic treatment for hemostasis is rarely required because bleeding from colorectal neoplasia is slow in the majority of patients.24

Postpolypectomy bleeding

  Postpolypectomy bleeding has been reported to account for 2% to 8% of acute LGIB.9,24 A recent large study of 50,000 colonoscopies that used Medicare claims data reported a bleeding rate of 8.7/1000 procedures.73 The adverse events of colonoscopy, including postpolypectomy bleeding, are discussed in another ASGE guideline.74

NSAID use

  NSAID use is associated with an increased risk of LGIB, including diverticular bleeding.31,75 A systematic review found that NSAID users had a significantly higher incidence of lower GI adverse events, including bleeding, compared with those who were not NSAID users.76 The prevalence of NSAID use is reported to be as high as 86% in patients with LGIB.77 The mechanisms involved in the induction of LGIB by NSAIDs are not well- understood and may include local mucosal trauma and platelet inhibition in susceptible individuals as well as the concomitant use of warfarin and other antiplatelet agents.78,79

Use of NSAIDs is associated with exacerbations of inflammatory bowel disease80,81 and can induce NSAID colopathy, which may be misdiagnosed as inflammatory bowel disease.82 This disorder is characterized by colon ulcerations and diaphragm-like strictures, predominantly located in the terminal ileum and right side of the colon. NSAID colopathy may be associated with adverse events of LGIB and perforation.82

Miscellaneous etiologies

  Rectal ulcers have been reported in 8% of patients who present with severe hematochezia83,84 and in 32% of patients who develop LGIB after intensive care unit admissions for other critical illnesses.85 Patients often have major medical comorbidities of end stage renal disease on hemodialysis, respiratory failure requiring mechanical ventilation, decompensated cirrhosis, or malignancy. Endoscopic findings range from clean-based ulcers (82%) to adherent clots (17%), nonbleeding visible vessels (33%), and active bleeding (50%).83 Early rebleeding after endoscopic treatment has been reported in 44% to 48% of patients, and a mortality rate of 33% to 48% has been reported in patients with high-risk stigmata who have multiple comorbidities.83,85

LGIB has been reported in 4% to 13% of patients with radiation proctopathy. This disorder is caused by radiation-induced endarteritis obliterans, which results in neovascularization and telangioectasias in the rectum.71

 

 Patients with inflammatory bowel disease commonly present with LGIB. Acute LGIB requiring hospitalization is uncommon and has been reported to account for only 1.2% to 6% of all admissions in patients with Crohn’s disease and 0.1% to 4.2% in patients with ulcerative colitis.86,87 Clinically significant bleeding in Crohn’s disease is more common in patients with colon involvement than in those with isolated small bowel disease.88 Bleeding resolves spontaneously in up to 50% of patients, but there is a recurrence rate of up to 35%.86 Medical management with biologics can be effective in the management of these patients.89,90

LGIB occurs in 2.6% of patients with HIV, usually in the setting of AIDS-related thrombocytopenia, and is associated with an inpatient mortality rate of 28%. The most common etiologies of LGIB in these patients are opportunistic infections, including cytomegalovirus, herpes simplex virus, Kaposi’s sarcoma, and idiopathic proctocolitis.91,92

 An upper GI source may be present in 11% to 15% of patients with suspected LGIB, whereas small-bowel sources constitute 2% to 15% of cases.35,93

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