Lower GI Bleed

• Most are diverticular; 75% stop spontaneously; resuscitate + CT angiography if ongoing brisk bleed.
• Positive CTA → catheter angiography with transcatheter arterial embolization; if CTA negative but bleeding persists, proceed to colonoscopy (after bowel prep) — tagged RBC scan mainly reserved for intermittent bleeding or when CTA unavailable.
• Reverse anticoagulation for life-threatening bleeding; resume anticoagulation as early as clinically appropriate after hemostasis, based on thrombotic and rebleeding risk.
• Small bowel sources: capsule or balloon enteroscopy after negative upper+lower studies.

Investigating Acute Lower Gastrointestinal Bleeding

• Bright or dark red blood in stool · maroon stool · melena
• Bloody diarrhea instead of acute LGIB?
• Send stool culture and sensitivity · stool testing for Shiga toxin-producing E. coli (STEC) by PCR and/or culture · C. difficile NAAT and/or toxin assay per institutional algorithm · consider inflammatory bowel disease · consider CMV colitis if immunosuppressed → give specific treatment as appropriate
• Hemodynamic compromise? Bloody NG aspirate? Aortoenteric fistula suspected?
• Upper endoscopy or enteroscopy — treat specifically as appropriate; urgent surgical consult when aortoenteric fistula is suspected even with negative endoscopy/enteroscopy
• Rapid ongoing bleeding? Hemodynamically unstable? Abnormal coagulation parameters? Unable to tolerate bowel preparation? Multiple comorbidities?
• CT angiography first; tagged RBC scan reserved for slower or intermittent bleeding
• CTA (or RBC scan) outcome?
• Is angiography tolerable for the patient?
• Angiography: catheter angiography with transcatheter arterial embolization when bleeding is localized (vasopressin infusion is historical — no longer recommended)
• Angiography outcome?
• Positive: watch for rebleeding · elective capsule study, CT or MR enterography when localized to small bowel · elective colonoscopy when localized to colon
• Negative → go to colonoscopy pathway
• Move to colonoscopy pathway
• Negative → move to colonoscopy pathway
• Prepare bowel with PEG · give through NG tube if appropriate
• Colonoscopy: apply endoscopic therapy as appropriate · refer for surgery as appropriate
• Colonoscopy negative with suspected small bowel source: capsule endoscopy · device-assisted enteroscopy (single- or double-balloon) when intervention is required after capsule endoscopy · CT enterography/angiography · MR enterography