A 43-year-old man presents to the emergency department with bright red blood in his stool this morning. He noticed this yesterday as well, but it was much scanter. The patient is otherwise healthy. He was celebrating his birthday last night and admits having "too much to drink" and vomited profusely overnight. He currently feels well and is not nauseous. He has no other significant medical history and does not take any medications. His temperature is 99.2°F (37.3°C), blood pressure is 110/75 mmHg, pulse is 82/min, respirations are 16/min, and oxygen saturation is 100% on room air. Physical exam reveals a nontender abdomen with normal bowel sounds. Rectal exam reveals grossly bloody stool. Laboratory studies are ordered as shown below.

Hemoglobin: 12 g/dL
Hematocrit: 36%
Leukocyte count: 5,500/mm^3 with normal differential
Platelet count: 179,000/mm^3

Which of the following is the most likely cause of this patient's symptoms?
Erosion into a gastric vessel
Submucosal esophageal tear
Vascular malformation
Malignancy
Vascular malformation
This patient is presenting with bright red blood per rectum with a non-tender abdomen. Of the answer choices given, angiodysplasia is the most likely to cause such profuse and sudden bleeding.

Angiodysplasia is a vascular malformation found in the gastrointestinal (GI) tract, most commonly in the colon. The exposed vessels can bleed, leading to bright red blood per rectum. The diagnosis can be confirmed with colonoscopy. Ablation can be performed to stop the bleeding. Any patient who is unstable or anemic with a hemoglobin < 7.0 g/dL requires a transfusion with blood products. Angiodysplasia is a common cause of bright red blood per rectum but is not more common than diverticulosis.

Garcia-Compeon et al. review the presentation and treatment of gastrointestinal angiodysplasia. The authors note that angiodysplasias are the cause of many "occult" GI bleeds not visualized on upper endoscopy or colonoscopy. The authors recommend the use of capsule endoscopy in occult GI bleeds to identify angiodysplasias as a potential source.

Incorrect Answers:
Answer A: Erosion into a gastric vessel is the pathophysiology of a bleeding gastric vessel secondary to peptic ulcer disease. This usually presents with melena (black tarry stools) rather than bright red blood per rectum. Only in cases of extremely brisk upper GI bleeding would patients present with bright red blood per rectum. Treatment involves treating Helicobacter pylori infection if present, proton pump inhibitors, and sucralfate. Endoscopy is needed to confirm and treat the bleeding vessel.

Answer B: Inflammation and infection of colonic outpouching is the pathophysiology of diverticulitis which presents with a history of constipation with a fever and left lower quadrant abdominal pain. Management involves a computed tomography (CT) scan of the abdomen/pelvis and administration of antibiotics (such as ciprofloxacin and metronidazole or ceftriaxone and metronidazole). Diverticulosis presents with bright red blood and is possible in this patient, but it does not involve inflammation or infection, which defines diverticulitis.

Answer C: Malignancy or colon cancer can present with bright red blood per rectum, malaise, weight loss, and microcytic anemia. While it is possible in this patient, his age, lack of risk factors for colon cancer, and the sudden onset of his symptoms make this diagnosis less likely.

Answer D: Submucosal esophageal (Mallory-Weiss) tear presents after profuse vomiting (as in this patient) with bloody vomitus. Treatment is supportive and involves antiemetics.

Bullet Summary:
Angiodysplasia is a vascular malformation that presents with bright red blood per rectum.