What are the causes of gastrointestinal (GI) bleed?

Etiology of Gastrointestinal Bleeding

Gastrointestinal bleeding etiologies vary dramatically by anatomic location (upper vs. lower GI tract) and patient age, with peptic ulcer disease being the leading cause of upper GI bleeding and diverticulosis/angiodysplasia dominating lower GI bleeding, particularly in patients over 70 years.

Upper GI Bleeding Causes (Proximal to Ligament of Treitz)

Most Common Etiologies

• Peptic ulcer disease (duodenal and gastric ulcers) represents the leading cause of nonvariceal upper GI bleeding, typically related to Helicobacter pylori infection or NSAID use 1, 2
• Gastric erosions and stress-related mucosal disease are particularly prevalent in critically ill patients with mechanical ventilation, coagulopathy, or renal failure 1
• Esophageal varices occur in patients with cirrhosis and represent the primary variceal bleeding source 1, 2
• Mallory-Weiss tears result from forceful vomiting or retching 1, 2

Frequently Overlooked Upper GI Lesions

• Cameron's erosions in large hiatal hernias 3
• Fundic varices 3
• Angioectasias (vascular malformations) 3, 1
• Dieulafoy's lesion - a tortuous submucosal artery penetrating the mucosa, commonly at the posterior gastric wall, accounting for 1-2% of acute bleeding 3, 1
• Gastric antral vascular ectasia (GAVE) 3
• Esophagitis and duodenitis 1

Neoplastic and Rare Causes

• Gastric cancer and hepatocellular carcinoma eroding into duodenum 1
• Hemosuccus pancreaticus - bleeding from pancreatic duct into duodenum, responsible for approximately 1 in 500 cases of upper GI bleeding 1, 4
• Hemobilia - bleeding into the biliary tree 1
• Aortoenteric fistula - rare but catastrophic 1

Iatrogenic Causes (ICU/Hospitalized Patients)

• Endoscopic complications including EUS-guided biopsies, ERCP-related injury, and delayed hemorrhage from biliary stenting 1
• Surgical complications such as extrahepatic arterial injury after pancreatic surgery and stomal marginal ulcers 1
• Esophageal or upper GI stent placement 1

Lower GI Bleeding Causes (Distal to Ligament of Treitz)

Age-Dependent Patterns

• Patients over 70 years: Colonic diverticula and angiodysplasia are the predominant causes 3, 5
• Younger patients: More likely to have inflammatory bowel disease (Crohn's disease) 3

Major Lower GI Etiologies

• Diverticulosis - represents a major cause of lower GI bleeding 5
• Vascular malformations/angiodysplasia 5
• Colorectal cancer 5
• Angioectasias - frequently missed during initial colonoscopy 3
• Radiation proctitis - occurs 9 months to 4 years after pelvic radiation therapy for prostatic or gynecologic malignancy 3

Mid GI (Small Bowel) Bleeding Causes

Age-Stratified Etiologies

• Younger patients (<40 years): Dieulafoy's lesion and Crohn's disease are most likely 3
• Older patients (>40 years): Vascular lesions comprise up to 40% of all causes, along with NSAID-induced small bowel disease 3

Small Bowel-Specific Causes

• Angiectasias - account for up to 80% of obscure bleeding cases 3, 6
• Small bowel tumors - most common cause of obscure bleeding in younger patients 3
• NSAID-induced ulcers 3, 6
• Small bowel diverticula 6
• Endometriosis 6

Rare Duodenal C-Loop Sources

• Hemobilia 3
• Hemosuccus pancreaticus 3
• Aortoenteric fistula 3

Critical Clinical Context

Epidemiologic Trends

• Upper GI bleeding incidence: 47/100,000 population 7
• Lower GI bleeding incidence: 33/100,000 population 7
• Upper GI bleeding incidence has fallen due to H. pylori eradication and proton pump inhibitor use, while lower GI bleeding incidence may be increasing 7

Obscure Bleeding

• Approximately 5% of patients with GI bleeding have no lesions identified by upper or lower endoscopy 6
• In 68% of patients presenting with GI bleeding without obvious source, the etiology remains unknown even after workup 8
• Bleeding stops spontaneously in 75-90% of cases 3, 1

Mortality and Rebleeding Risk

• Upper GI bleeding carries 2-14% mortality risk despite spontaneous cessation in 75% of cases 1
• Lower GI bleeding patients may have longer hospital stays and potentially higher risk of death or rebleeding compared to historical data 7

Key Clinical Pitfalls

• Nasogastric aspirate may be negative in 3-16% of patients with confirmed upper GI bleeding 1
• Approximately 40% of rectal carcinomas are palpable on digital rectal examination, making this examination essential 3
• The old dogma that "the most common cause of lower GI bleeding is upper GI bleeding" may no longer be valid with modern PPI and H. pylori treatment 8
• 17% of patients presenting with lower GI symptoms actually have an upper GI source 8