How GI bleeding is tested on Step 1
Questions give a bleeding pattern plus age and context, and ask for the source or mechanism.
Upper GI causes
Know the classic vignette for each.
| Cause | Classic clue |
|---|---|
| Peptic ulcer disease | NSAIDs or H. pylori; epigastric pain; posterior duodenal ulcer → gastroduodenal artery |
| Esophageal varices | Cirrhosis and portal hypertension; massive painless hematemesis |
| Mallory-Weiss tear | Hematemesis after repeated retching, often with alcohol |
| Boerhaave syndrome | Vomiting → severe chest pain, subcutaneous emphysema, pneumomediastinum; a surgical emergency |
| Erosive gastritis | NSAIDs, alcohol, critical illness (stress ulcers) |
| Dieulafoy lesion | Large tortuous submucosal artery, usually in the stomach; recurrent brisk bleeding |
Aortoenteric fistula is a rare cause after aortic graft surgery, often heralded by a small "herald" bleed.
Lower GI causes
Age shapes the differential.
| Cause | Key feature |
|---|---|
| Diverticulosis | Painless, often large-volume bleeding from a vasa recta at the diverticular neck |
| Angiodysplasia | Older adults; cecum and ascending colon; associated with aortic stenosis and ESKD |
| Colorectal cancer | Occult bleeding (right side) or hematochezia (left side) |
| Ischemic colitis | Pain then bloody diarrhea; watershed areas (splenic flexure, rectosigmoid junction) |
| Hemorrhoids | Bright red blood on the toilet paper; internal hemorrhoids are painless |
| Meckel diverticulum | Rule of 2s: about 2% of people, within about 2 feet of the ileocecal valve, often symptomatic before age 2 |
Diverticulitis (inflammation) usually causes pain and fever, not major bleeding; diverticulosis bleeds without pain.
Initial approach
Physiology drives the first steps.
- Assess and support airway and circulation: two large-bore IVs, crystalloid, and blood products as needed.
- Tachycardia and orthostatic changes appear before hypotension; hemoglobin may not fall until fluid shifts or resuscitation.
- Upper bleeding: IV PPI and endoscopy; suspected variceal bleeding adds octreotide and antibiotics.
- Lower bleeding: colonoscopy after bowel preparation; angiography or a tagged red cell scan for brisk or obscure bleeding.
Worked example
Pick the cause from age and context.
functions Worked example — painless bleeding in a toddler
A 2-year-old has large-volume, painless, maroon stools. The abdomen is soft and nontender. Which test confirms the most likely diagnosis, and why does it work?
- Painless lower GI bleeding in a young child suggests Meckel diverticulum.
- It is a true diverticulum from persistence of the vitelline (omphalomesenteric) duct.
- Ectopic gastric mucosa secretes acid, ulcerating the adjacent ileum.
- Technetium-99m pertechnetate is taken up by gastric mucosa, showing the ectopic tissue.
Answer. Meckel diverticulum, confirmed with a technetium-99m pertechnetate (Meckel) scan.
