Differential Diagnoses for Gastrointestinal Bleeding
Gastrointestinal bleeding divides into upper GI (proximal to ligament of Treitz) and lower GI sources, with peptic ulcer disease being the most common cause of upper GI bleeding, while diverticulosis and angiodysplasia dominate lower GI bleeding.
Upper Gastrointestinal Bleeding (UGIB) Differentials
Most Common Causes
- Peptic ulcer disease - the leading cause of UGIB, driven by H. pylori infection and NSAID use 1
- Esophageal varices - in patients with portal hypertension/cirrhosis
- Mallory-Weiss tears - following forceful vomiting
- Erosive esophagitis/gastritis - often medication-related
Less Common but Critical Causes
- Dieulafoy lesion - aberrant submucosal artery that erodes through mucosa 1
- Gastric antral vascular ectasia (GAVE) - "watermelon stomach"
- Upper GI malignancies - gastric or esophageal cancer 1
- Aortoenteric fistula - particularly in patients with prior aortic graft surgery 1
- Hemobilia - bleeding from biliary tree 1
- Post-esophagectomy gastric conduit hemorrhage 2
- Pancreatic cancer with vascular erosion 2
Lower Gastrointestinal Bleeding (LGIB) Differentials
Key Diagnostic Consideration
10-15% of patients presenting with apparent LGIB (brisk rectal bleeding with hemodynamic compromise) actually have an upper GI source 3. Risk factors suggesting UGIB masquerading as LGIB include:
- Brisk rectal bleeding with shock
- History of peptic ulcer disease or portal hypertension
- Elevated BUN/creatinine ratio
- Antiplatelet drug use 3
Common Lower GI Sources
- Diverticular bleeding - most common cause in adults
- Angiodysplasia/vascular ectasia - especially in elderly
- Ischemic colitis
- Inflammatory bowel disease (Crohn's, ulcerative colitis)
- Colorectal polyps and cancer
- Hemorrhoids and anal fissures - typically minor bleeding
- Post-polypectomy bleeding - iatrogenic but important cause 3
Obscure Gastrointestinal Bleeding
When upper endoscopy and colonoscopy are negative, consider small bowel sources 4:
- Small bowel angiodysplasia
- Small bowel tumors (carcinoid, GIST, adenocarcinoma)
- Meckel's diverticulum
- Small bowel Crohn's disease
- NSAID-induced enteropathy
Diagnostic Approach for Obscure Bleeding
Video capsule endoscopy should be the next diagnostic modality after negative high-quality upper and lower endoscopy 3. Diagnostic yield is highest (87-92%) when performed within 48 hours of bleeding but drops below 50% after 3 days 3.
Critical Clinical Pitfalls
Don't assume rectal bleeding is lower GI - always consider upper GI source in unstable patients with brisk bleeding 3
Nasogastric tube placement is NOT recommended - it doesn't reliably aid diagnosis, doesn't affect outcomes, and causes complications in one-third of patients 3
Timing matters for capsule endoscopy - delay beyond 48-72 hours significantly reduces diagnostic yield 3
Post-polypectomy bleeding requires colonoscopy first, not CTA, even in unstable patients since the source is already known 3