Colonoscopy

• A colonoscopy should be performed after complete colon cleansing and when the patient is hemodynamically stable.
  • Administer 4 to 6 liters of a polyethylene glycol-based solution or the equivalent over 3 to 4 hours until the rectal output is clear of blood and stool.

• An unprepped colonoscopy/sigmoidoscopy is not recommended.
• A nasogastric tube may be inserted in high-risk patients who have ongoing bleeding, who are unable to tolerate oral intake, and who are at a high risk for aspiration.
• Administer a prokinetic/antiemetic agent immediately before the colon preparation to reduce nausea and facilitate gastric emptying.
• Complications of colon preparation with polyethylene glycol include aspiration pneumonia and fluid and electrolyte abnormalities. Aspiration precautions should be taken, especially in older and/or debilitated patients. 

• In high-risk patients or if there are signs of ongoing bleeding, perform a rapid bowel preparation after fluid resuscitation. A colonoscopy should be performed within 24 hours of patient presentation and after adequate colon preparation.
• In patients without high-risk clinical features or serious comorbidities, or in those with high-risk clinical features but without signs or symptoms of ongoing bleeding, a colonoscopy may be performed less urgently after adequate blood transfusion and colon preparation.

• Endoscopic therapy is performed during colonoscopy on patients with active bleeding (spurting and oozing), a nonbleeding visible vessel, or an adherent clot.
• Diverticular bleeding 
  • May present as painless hematochezia, usually originating from a diverticulum
  • Treated with endoscopic clips which may be safer in the colon than contact thermal therapy (cauterization) and easier to perform than band ligation
• Angioectasia (vascular malformation) bleeding 
  • Common in the right colon and in the elderly
  • Presents with occult bleeding or overt hematochezia, especially in patients on anticoagulant/antiplatelet therapy
  • Treated with noncontact thermal therapy
• Postpolypectomy bleeding 
  • This can occur immediately, days, or weeks following polyp removal.
  • Risk factors include:
    • Large polyp size (greater than 2 cm)
    • Thick stalk
    • Right colon location
    • Resumption of antithrombotic therapy
  • Treated with mechanical clip or contact thermal therapy with or without the combined use of dilute epinephrine injection
• Epinephrine injection may be used to improve visualization and control actively bleeding lesions.
  • Should only be used with another hemostasis therapy such as mechanical or contact therapy to stop bleeding
• Ischemic colitis, colitis due to inflammatory bowel disease, and colorectal neoplasms do not respond to endoscopic hemostasis and are usually treated with supportive medical and/or surgical care.

• Repeat colonoscopy with endoscopic hemostasis may be needed for patients with evidence of recurrent bleeding.
• Late rebleeding may be caused by:
  • Underlying comorbid conditions
  • Concurrent medication use (i.e., NSAIDs, antiplatelet agents, anticoagulants)
  • Reactivation of the source of the bleeding
  • Failure of the initial method of hemostasis

Non-Colonoscopy Interventions

• Consider radiographic interventions in patients with the following:
  • High-risk clinical features
  • Ongoing bleeding with a negative upper endoscopy
  • Inadequate response to hemodynamic resuscitation efforts (these patients are unlikely to tolerate bowel preparation and an urgent colonoscopy)
• Computed tomographic (CT) angiography should be considered if a diagnostic test is needed for localization of the bleeding site before angiography. CT angiography is useful in patients with ongoing bleeding who are not hemodynamically stable enough to withstand a bowel preparation prior to colonoscopy.
• Radionuclide imaging (also known as a tagged red blood cell scan) can detect focal collections of radiolabeled material. It can be performed relatively quickly and may help localize the general area of bleeding to guide subsequent endoscopy, angiography, or surgery. Radionuclide imaging can only detect active bleeding and is limited by the lack of therapeutic capabilities. Therefore, this modality has a complementary role in the evaluation of colonic or small bowel bleeding. 
• Mesenteric angiography allows for interventions to stop localized intestinal bleeding such as injection of vasoconstrictors or super-selective embolization of distal arterial branches. It may be best suited for massive LGIB such that the patient cannot be stabilized to permit adequate bowel preparation and performance of colonoscopy. Angiography may be preceded by CT angiography, a tagged red blood cell scan, or capsule endoscopy to assist in localization of the bleeding site.
• Request a surgical consultation for high-risk patients with ongoing bleeding.
  • Consider surgery for acute LGIB after other therapeutic options have failed.
  • Localize the source of bleeding before surgical resection to avoid continued or recurrent bleeding from an unresected lesion.

Prevention of Recurrent Lower GI Bleeding and Cardiac Risk Factors

• Avoid NSAID use in patients with a history of acute LGIB.
• Do not discontinue aspirin for secondary prevention in patients with high-risk cardiovascular disease and a history of LGIB. Using aspirin for primary prevention of cardiovascular events should be avoided in most patients with LGIB.
• For patients on dual antiplatelet therapy or monotherapy with non-aspirin antiplatelet agents (thienopyridine), non-aspirin antiplatelet therapy should be resumed within 7 days. Dual antiplatelet therapy should not be discontinued in patients with an acute coronary syndrome within the past 90 days or coronary stenting within the past 30 days.