Review Question - QID 108848

A 69-year-old male presents to his primary care physician complaining of fatigue. He reports that over the past four months, he has felt worsening tiredness and generalized weakness. His past medical history is notable for aortic stenosis, hypertension, and diabetes mellitus. Physical examination is notable for conjunctival pallor, delayed capillary refill, and a crescendo-decrescendo murmur at the upper right sternal border. A complete blood count reveals a hemoglobin of 8.9 g/dL and hematocrit of 30%. A stool sample is positive for heme. A colonoscopy is performed and an image from the ascending colon is shown in Figure A. Which of the following mechanisms has most likely contributed to this patient’s condition?