Review Question - QID 212567

A 27-year-old man presents to the emergency department with a chief concern of abdominal pain and diarrhea. The patient states that for the past 4 days he has experienced abdominal pain, diarrhea, weakness and a subjective fever. He also endorses a weight loss of 11 pounds during this time. The patient has a past medical history of celiac disease, constipation, and depression. His current medications include fish oil, a multivitamin, sodium docusate, and fluoxetine. His temperature is 98.5°F (36.9°C), blood pressure is 110/75 mmHg, pulse is 90/min, respirations are 13/min, and oxygen saturation is 98% on room air. Physical exam is notable for a young man in mild distress. Cardiac and pulmonary exams are within normal limits. Abdominal exam is notable for generalized tenderness and increased bowel sounds. Oral exam is notable for multiple shallow painful ulcers. Laboratory values are ordered as seen below:

Hemoglobin: 12 g/dL
Hematocrit: 36%
Leukocyte count: 8,000 cells/mm^3 with normal differential
Platelet count: 227,500/mm^3

Serum:
Na+: 141 mEq/L
Cl-: 101 mEq/L
K+: 4.5 mEq/L
HCO3-: 24 mEq/L
BUN: 17 mg/dL
Glucose: 82 mg/dL
Creatinine: 1.0 mg/dL
Ca2+: 10.1 mg/dL
AST: 12 U/L
ALT: 11 U/L

A stool guaiac test is performed which returns positive. The patient is started on IV fluids and morphine. Which of the following best describes the most likely diagnosis?